Auto merge of #63627 - Centril:rollup-v8i7x5i, r=Centril

Rollup of 7 pull requests

Successful merges:

 - #62593 (Group all ABI tests.)
 - #63173 (Use libunwind from llvm-project submodule for musl targets)
 - #63535 (Continue refactoring resolve and hygiene)
 - #63539 (Suggest Rust 2018 on `<expr>.await` with no such field)
 - #63584 (libcore: more cleanups using `#![feature(associated_type_bounds)]`)
 - #63612 (Do not suggest `try_into` for base types inside of macro expansions)
 - #63615 (Fix typo in DoubleEndedIterator::nth_back doc)

Failed merges:

r? @ghost

src/bootstrap/sanity.rs

@@ -202,10 +202,6 @@ pub fn check(build: &mut Build) {
                         panic!("couldn't find libc.a in musl dir: {}",
                                root.join("lib").display());
                     }
-                    if fs::metadata(root.join("lib/libunwind.a")).is_err() {
-                        panic!("couldn't find libunwind.a in musl dir: {}",
-                               root.join("lib").display());
-                    }
                 }
                 None => {
                     panic!("when targeting MUSL either the rust.musl-root \

src/ci/docker/scripts/musl-toolchain.sh

@@ -54,29 +54,3 @@ if [ "$REPLACE_CC" = "1" ]; then
         ln -s $TARGET-g++ /usr/local/bin/$exec
     done
 fi
-
-export CC=$TARGET-gcc
-export CXX=$TARGET-g++
-
-LLVM=70
-
-# may have been downloaded in a previous run
-if [ ! -d libunwind-release_$LLVM ]; then
-  curl -L https://github.com/llvm-mirror/llvm/archive/release_$LLVM.tar.gz | tar xzf -
-  curl -L https://github.com/llvm-mirror/libunwind/archive/release_$LLVM.tar.gz | tar xzf -
-fi
-
-# fixme(mati865): Replace it with https://github.com/rust-lang/rust/pull/59089
-mkdir libunwind-build
-cd libunwind-build
-cmake ../libunwind-release_$LLVM \
-          -DLLVM_PATH=/build/llvm-release_$LLVM \
-          -DLIBUNWIND_ENABLE_SHARED=0 \
-          -DCMAKE_C_COMPILER=$CC \
-          -DCMAKE_CXX_COMPILER=$CXX \
-          -DCMAKE_C_FLAGS="$CFLAGS" \
-          -DCMAKE_CXX_FLAGS="$CXXFLAGS"
-
-hide_output make -j$(nproc)
-cp lib/libunwind.a $OUTPUT/$TARGET/lib
-cd - && rm -rf libunwind-build

src/ci/docker/scripts/musl.sh

@@ -20,6 +20,8 @@ exit 1
 TAG=$1
 shift
 
+# Ancient binutils versions don't understand debug symbols produced by more recent tools.
+# Apparently applying `-fPIC` everywhere allows them to link successfully.
 export CFLAGS="-fPIC $CFLAGS"
 
 MUSL=musl-1.1.22
@@ -38,27 +40,3 @@ else
 fi
 hide_output make install
 hide_output make clean
-
-cd ..
-
-LLVM=70
-
-# may have been downloaded in a previous run
-if [ ! -d libunwind-release_$LLVM ]; then
-  curl -L https://github.com/llvm-mirror/llvm/archive/release_$LLVM.tar.gz | tar xzf -
-  curl -L https://github.com/llvm-mirror/libunwind/archive/release_$LLVM.tar.gz | tar xzf -
-fi
-
-mkdir libunwind-build
-cd libunwind-build
-cmake ../libunwind-release_$LLVM \
-          -DLLVM_PATH=/build/llvm-release_$LLVM \
-          -DLIBUNWIND_ENABLE_SHARED=0 \
-          -DCMAKE_C_COMPILER=$CC \
-          -DCMAKE_CXX_COMPILER=$CXX \
-          -DCMAKE_C_FLAGS="$CFLAGS" \
-          -DCMAKE_CXX_FLAGS="$CXXFLAGS"
-
-hide_output make -j$(nproc)
-cp lib/libunwind.a /musl-$TAG/lib
-cd ../ && rm -rf libunwind-build

src/libcore/iter/adapters/flatten.rs

@@ -72,8 +72,7 @@ impl<I: Iterator, U: IntoIterator, F> Iterator for FlatMap<I, U, F>
 impl<I: DoubleEndedIterator, U, F> DoubleEndedIterator for FlatMap<I, U, F>
 where
     F: FnMut(I::Item) -> U,
-    U: IntoIterator,
+    U: IntoIterator<IntoIter: DoubleEndedIterator>,
-    U::IntoIter: DoubleEndedIterator,
 {
     #[inline]
     fn next_back(&mut self) -> Option<U::Item> { self.inner.next_back() }
@@ -107,10 +106,7 @@ impl<I, U, F> FusedIterator for FlatMap<I, U, F>
 /// [`Iterator`]: trait.Iterator.html
 #[must_use = "iterators are lazy and do nothing unless consumed"]
 #[stable(feature = "iterator_flatten", since = "1.29.0")]
-pub struct Flatten<I: Iterator>
+pub struct Flatten<I: Iterator<Item: IntoIterator>> {
-where
-    I::Item: IntoIterator,
-{
     inner: FlattenCompat<I, <I::Item as IntoIterator>::IntoIter>,
 }
 

src/libcore/iter/traits/double_ended.rs

@@ -69,7 +69,7 @@ pub trait DoubleEndedIterator: Iterator {
     /// Returns the `n`th element from the end of the iterator.
     ///
     /// This is essentially the reversed version of [`nth`]. Although like most indexing
-    /// operations, the count starts from zero, so `nth_back(0)` returns the first value fro
+    /// operations, the count starts from zero, so `nth_back(0)` returns the first value from
     /// the end, `nth_back(1)` the second, and so on.
     ///
     /// Note that all elements between the end and the returned element will be

src/librustc/hir/lowering.rs

@@ -67,7 +67,7 @@ use syntax::errors;
 use syntax::ext::base::SpecialDerives;
 use syntax::ext::hygiene::ExpnId;
 use syntax::print::pprust;
-use syntax::source_map::{respan, ExpnInfo, ExpnKind, DesugaringKind, Spanned};
+use syntax::source_map::{respan, ExpnData, ExpnKind, DesugaringKind, Spanned};
 use syntax::symbol::{kw, sym, Symbol};
 use syntax::tokenstream::{TokenStream, TokenTree};
 use syntax::parse::token::{self, Token};
@@ -704,10 +704,9 @@ impl<'a> LoweringContext<'a> {
         span: Span,
         allow_internal_unstable: Option<Lrc<[Symbol]>>,
     ) -> Span {
-        span.fresh_expansion(ExpnId::root(), ExpnInfo {
+        span.fresh_expansion(ExpnData {
-            def_site: span,
             allow_internal_unstable,
-            ..ExpnInfo::default(ExpnKind::Desugaring(reason), span, self.sess.edition())
+            ..ExpnData::default(ExpnKind::Desugaring(reason), span, self.sess.edition())
         })
     }
 
@@ -1224,7 +1223,7 @@ impl<'a> LoweringContext<'a> {
                     P(hir::Path {
                         res,
                         segments: hir_vec![hir::PathSegment::from_ident(
-                            Ident::with_empty_ctxt(kw::SelfUpper)
+                            Ident::with_dummy_span(kw::SelfUpper)
                         )],
                         span: t.span,
                     }),
@@ -1558,7 +1557,7 @@ impl<'a> LoweringContext<'a> {
 
                     let (name, kind) = match name {
                         hir::LifetimeName::Underscore => (
-                            hir::ParamName::Plain(Ident::with_empty_ctxt(kw::UnderscoreLifetime)),
+                            hir::ParamName::Plain(Ident::with_dummy_span(kw::UnderscoreLifetime)),
                             hir::LifetimeParamKind::Elided,
                         ),
                         hir::LifetimeName::Param(param_name) => (
@@ -2002,7 +2001,7 @@ impl<'a> LoweringContext<'a> {
                         bindings: hir_vec![
                             hir::TypeBinding {
                                 hir_id: this.next_id(),
-                                ident: Ident::with_empty_ctxt(FN_OUTPUT_NAME),
+                                ident: Ident::with_dummy_span(FN_OUTPUT_NAME),
                                 kind: hir::TypeBindingKind::Equality {
                                     ty: output
                                         .as_ref()
@@ -2394,7 +2393,7 @@ impl<'a> LoweringContext<'a> {
         let future_params = P(hir::GenericArgs {
             args: hir_vec![],
             bindings: hir_vec![hir::TypeBinding {
-                ident: Ident::with_empty_ctxt(FN_OUTPUT_NAME),
+                ident: Ident::with_dummy_span(FN_OUTPUT_NAME),
                 kind: hir::TypeBindingKind::Equality {
                     ty: output_ty,
                 },

src/librustc/hir/lowering/expr.rs

@@ -552,7 +552,7 @@ impl LoweringContext<'_> {
 
         // let mut pinned = <expr>;
         let expr = P(self.lower_expr(expr));
-        let pinned_ident = Ident::with_empty_ctxt(sym::pinned);
+        let pinned_ident = Ident::with_dummy_span(sym::pinned);
         let (pinned_pat, pinned_pat_hid) = self.pat_ident_binding_mode(
             span,
             pinned_ident,
@@ -593,7 +593,7 @@ impl LoweringContext<'_> {
         let loop_node_id = self.sess.next_node_id();
         let loop_hir_id = self.lower_node_id(loop_node_id);
         let ready_arm = {
-            let x_ident = Ident::with_empty_ctxt(sym::result);
+            let x_ident = Ident::with_dummy_span(sym::result);
             let (x_pat, x_pat_hid) = self.pat_ident(span, x_ident);
             let x_expr = P(self.expr_ident(span, x_ident, x_pat_hid));
             let ready_pat = self.pat_std_enum(
@@ -1070,9 +1070,9 @@ impl LoweringContext<'_> {
         );
         head.span = desugared_span;
 
-        let iter = Ident::with_empty_ctxt(sym::iter);
+        let iter = Ident::with_dummy_span(sym::iter);
 
-        let next_ident = Ident::with_empty_ctxt(sym::__next);
+        let next_ident = Ident::with_dummy_span(sym::__next);
         let (next_pat, next_pat_hid) = self.pat_ident_binding_mode(
             desugared_span,
             next_ident,
@@ -1081,7 +1081,7 @@ impl LoweringContext<'_> {
 
         // `::std::option::Option::Some(val) => __next = val`
         let pat_arm = {
-            let val_ident = Ident::with_empty_ctxt(sym::val);
+            let val_ident = Ident::with_dummy_span(sym::val);
             let (val_pat, val_pat_hid) = self.pat_ident(pat.span, val_ident);
             let val_expr = P(self.expr_ident(pat.span, val_ident, val_pat_hid));
             let next_expr = P(self.expr_ident(pat.span, next_ident, next_pat_hid));
@@ -1247,7 +1247,7 @@ impl LoweringContext<'_> {
 
         // `Ok(val) => #[allow(unreachable_code)] val,`
         let ok_arm = {
-            let val_ident = Ident::with_empty_ctxt(sym::val);
+            let val_ident = Ident::with_dummy_span(sym::val);
             let (val_pat, val_pat_nid) = self.pat_ident(span, val_ident);
             let val_expr = P(self.expr_ident_with_attrs(
                 span,
@@ -1263,7 +1263,7 @@ impl LoweringContext<'_> {
         // `Err(err) => #[allow(unreachable_code)]
         //              return Try::from_error(From::from(err)),`
         let err_arm = {
-            let err_ident = Ident::with_empty_ctxt(sym::err);
+            let err_ident = Ident::with_dummy_span(sym::err);
             let (err_local, err_local_nid) = self.pat_ident(try_span, err_ident);
             let from_expr = {
                 let from_path = &[sym::convert, sym::From, sym::from];

src/librustc/hir/mod.rs

@@ -202,7 +202,7 @@ impl ParamName {
         match *self {
             ParamName::Plain(ident) => ident,
             ParamName::Fresh(_) |
-            ParamName::Error => Ident::with_empty_ctxt(kw::UnderscoreLifetime),
+            ParamName::Error => Ident::with_dummy_span(kw::UnderscoreLifetime),
         }
     }
 
@@ -237,8 +237,8 @@ impl LifetimeName {
     pub fn ident(&self) -> Ident {
         match *self {
             LifetimeName::Implicit | LifetimeName::Error => Ident::invalid(),
-            LifetimeName::Underscore => Ident::with_empty_ctxt(kw::UnderscoreLifetime),
+            LifetimeName::Underscore => Ident::with_dummy_span(kw::UnderscoreLifetime),
-            LifetimeName::Static => Ident::with_empty_ctxt(kw::StaticLifetime),
+            LifetimeName::Static => Ident::with_dummy_span(kw::StaticLifetime),
             LifetimeName::Param(param_name) => param_name.ident(),
         }
     }

src/librustc/hir/print.rs

@@ -1457,7 +1457,7 @@ impl<'a> State<'a> {
     }
 
     pub fn print_name(&mut self, name: ast::Name) {
-        self.print_ident(ast::Ident::with_empty_ctxt(name))
+        self.print_ident(ast::Ident::with_dummy_span(name))
     }
 
     pub fn print_for_decl(&mut self, loc: &hir::Local, coll: &hir::Expr) {

src/librustc/ich/hcx.rs

@@ -350,7 +350,7 @@ impl<'a> HashStable<StableHashingContext<'a>> for Span {
         let line_col_len = col | line | len;
         std_hash::Hash::hash(&line_col_len, hasher);
 
-        if span.ctxt == SyntaxContext::empty() {
+        if span.ctxt == SyntaxContext::root() {
             TAG_NO_EXPANSION.hash_stable(hcx, hasher);
         } else {
             TAG_EXPANSION.hash_stable(hcx, hasher);
@@ -370,7 +370,7 @@ impl<'a> HashStable<StableHashingContext<'a>> for Span {
                 }
 
                 let mut hasher = StableHasher::new();
-                expn_id.expn_info().hash_stable(hcx, &mut hasher);
+                expn_id.expn_data().hash_stable(hcx, &mut hasher);
                 let sub_hash: Fingerprint = hasher.finish();
                 let sub_hash = sub_hash.to_smaller_hash();
                 cache.borrow_mut().insert(expn_id, sub_hash);

src/librustc/ich/impls_syntax.rs

@@ -397,9 +397,10 @@ impl_stable_hash_for!(enum ::syntax_pos::hygiene::Transparency {
     Opaque,
 });
 
-impl_stable_hash_for!(struct ::syntax_pos::hygiene::ExpnInfo {
+impl_stable_hash_for!(struct ::syntax_pos::hygiene::ExpnData {
-    call_site,
     kind,
+    parent -> _,
+    call_site,
     def_site,
     default_transparency,
     allow_internal_unstable,

src/librustc/lint/internal.rs

@@ -9,7 +9,6 @@ use errors::Applicability;
 use rustc_data_structures::fx::FxHashMap;
 use syntax::ast::{Ident, Item, ItemKind};
 use syntax::symbol::{sym, Symbol};
-use syntax_pos::ExpnInfo;
 
 declare_tool_lint! {
     pub rustc::DEFAULT_HASH_TYPES,
@@ -108,7 +107,7 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TyTyKind {
                             .help("try using `Ty` instead")
                             .emit();
                         } else {
-                            if ty.span.ctxt().outer_expn_info().is_some() {
+                            if ty.span.from_expansion() {
                                 return;
                             }
                             if let Some(t) = is_ty_or_ty_ctxt(cx, ty) {
@@ -228,30 +227,20 @@ impl EarlyLintPass for LintPassImpl {
         if let ItemKind::Impl(_, _, _, _, Some(lint_pass), _, _) = &item.node {
             if let Some(last) = lint_pass.path.segments.last() {
                 if last.ident.name == sym::LintPass {
-                    match &lint_pass.path.span.ctxt().outer_expn_info() {
+                    let expn_data = lint_pass.path.span.ctxt().outer_expn_data();
-                        Some(info) if is_lint_pass_expansion(info) => {}
+                    let call_site = expn_data.call_site;
-                        _ => {
+                    if expn_data.kind.descr() != sym::impl_lint_pass &&
-                            cx.struct_span_lint(
+                       call_site.ctxt().outer_expn_data().kind.descr() != sym::declare_lint_pass {
-                                LINT_PASS_IMPL_WITHOUT_MACRO,
+                        cx.struct_span_lint(
-                                lint_pass.path.span,
+                            LINT_PASS_IMPL_WITHOUT_MACRO,
-                                "implementing `LintPass` by hand",
+                            lint_pass.path.span,
-                            )
+                            "implementing `LintPass` by hand",
-                            .help("try using `declare_lint_pass!` or `impl_lint_pass!` instead")
+                        )
-                            .emit();
+                        .help("try using `declare_lint_pass!` or `impl_lint_pass!` instead")
-                        }
+                        .emit();
                     }
                 }
             }
         }
     }
 }
-
-fn is_lint_pass_expansion(expn_info: &ExpnInfo) -> bool {
-    if expn_info.kind.descr() == sym::impl_lint_pass {
-        true
-    } else if let Some(info) = expn_info.call_site.ctxt().outer_expn_info() {
-        info.kind.descr() == sym::declare_lint_pass
-    } else {
-        false
-    }
-}

src/librustc/lint/mod.rs

@@ -885,21 +885,16 @@ pub fn provide(providers: &mut Providers<'_>) {
 /// This is used to test whether a lint should not even begin to figure out whether it should
 /// be reported on the current node.
 pub fn in_external_macro(sess: &Session, span: Span) -> bool {
-    let info = match span.ctxt().outer_expn_info() {
+    let expn_data = span.ctxt().outer_expn_data();
-        Some(info) => info,
+    match expn_data.kind {
-        // no ExpnInfo means this span doesn't come from a macro
-        None => return false,
-    };
-
-    match info.kind {
         ExpnKind::Root | ExpnKind::Desugaring(DesugaringKind::ForLoop) => false,
         ExpnKind::Desugaring(_) => true, // well, it's "external"
         ExpnKind::Macro(MacroKind::Bang, _) => {
-            if info.def_site.is_dummy() {
+            if expn_data.def_site.is_dummy() {
                 // dummy span for the def_site means it's an external macro
                 return true;
             }
-            match sess.source_map().span_to_snippet(info.def_site) {
+            match sess.source_map().span_to_snippet(expn_data.def_site) {
                 Ok(code) => !code.starts_with("macro_rules"),
                 // no snippet = external macro or compiler-builtin expansion
                 Err(_) => true,
@@ -911,10 +906,8 @@ pub fn in_external_macro(sess: &Session, span: Span) -> bool {
 
 /// Returns whether `span` originates in a derive macro's expansion
 pub fn in_derive_expansion(span: Span) -> bool {
-    if let Some(info) = span.ctxt().outer_expn_info() {
+    if let ExpnKind::Macro(MacroKind::Derive, _) = span.ctxt().outer_expn_data().kind {
-        if let ExpnKind::Macro(MacroKind::Derive, _) = info.kind {
+        return true;
-            return true;
-        }
     }
     false
 }

src/librustc/traits/error_reporting.rs

@@ -36,7 +36,7 @@ use errors::{Applicability, DiagnosticBuilder};
 use std::fmt;
 use syntax::ast;
 use syntax::symbol::sym;
-use syntax_pos::{DUMMY_SP, Span, ExpnInfo, ExpnKind};
+use syntax_pos::{DUMMY_SP, Span, ExpnKind};
 
 impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
     pub fn report_fulfillment_errors(&self,
@@ -61,9 +61,9 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
             // We want to ignore desugarings here: spans are equivalent even
             // if one is the result of a desugaring and the other is not.
             let mut span = error.obligation.cause.span;
-            if let Some(ExpnInfo { kind: ExpnKind::Desugaring(_), def_site, .. })
+            let expn_data = span.ctxt().outer_expn_data();
-                    = span.ctxt().outer_expn_info() {
+            if let ExpnKind::Desugaring(_) = expn_data.kind {
-                span = def_site;
+                span = expn_data.call_site;
             }
 
             error_map.entry(span).or_default().push(

src/librustc/traits/project.rs

@@ -1417,7 +1417,7 @@ fn confirm_callable_candidate<'cx, 'tcx>(
                 projection_ty: ty::ProjectionTy::from_ref_and_name(
                     tcx,
                     trait_ref,
-                    Ident::with_empty_ctxt(FN_OUTPUT_NAME),
+                    Ident::with_dummy_span(FN_OUTPUT_NAME),
                 ),
                 ty: ret_type
             }

src/librustc/ty/query/on_disk_cache.rs

@@ -23,16 +23,16 @@ use std::mem;
 use syntax::ast::NodeId;
 use syntax::source_map::{SourceMap, StableSourceFileId};
 use syntax_pos::{BytePos, Span, DUMMY_SP, SourceFile};
-use syntax_pos::hygiene::{ExpnId, SyntaxContext, ExpnInfo};
+use syntax_pos::hygiene::{ExpnId, SyntaxContext, ExpnData};
 
 const TAG_FILE_FOOTER: u128 = 0xC0FFEE_C0FFEE_C0FFEE_C0FFEE_C0FFEE;
 
 const TAG_CLEAR_CROSS_CRATE_CLEAR: u8 = 0;
 const TAG_CLEAR_CROSS_CRATE_SET: u8 = 1;
 
-const TAG_NO_EXPANSION_INFO: u8 = 0;
+const TAG_NO_EXPN_DATA: u8 = 0;
-const TAG_EXPANSION_INFO_SHORTHAND: u8 = 1;
+const TAG_EXPN_DATA_SHORTHAND: u8 = 1;
-const TAG_EXPANSION_INFO_INLINE: u8 = 2;
+const TAG_EXPN_DATA_INLINE: u8 = 2;
 
 const TAG_VALID_SPAN: u8 = 0;
 const TAG_INVALID_SPAN: u8 = 1;
@@ -58,7 +58,7 @@ pub struct OnDiskCache<'sess> {
 
     // These two fields caches that are populated lazily during decoding.
     file_index_to_file: Lock<FxHashMap<SourceFileIndex, Lrc<SourceFile>>>,
-    synthetic_expansion_infos: Lock<FxHashMap<AbsoluteBytePos, SyntaxContext>>,
+    synthetic_syntax_contexts: Lock<FxHashMap<AbsoluteBytePos, SyntaxContext>>,
 
     // A map from dep-node to the position of the cached query result in
     // `serialized_data`.
@@ -135,7 +135,7 @@ impl<'sess> OnDiskCache<'sess> {
             current_diagnostics: Default::default(),
             query_result_index: footer.query_result_index.into_iter().collect(),
             prev_diagnostics_index: footer.diagnostics_index.into_iter().collect(),
-            synthetic_expansion_infos: Default::default(),
+            synthetic_syntax_contexts: Default::default(),
             alloc_decoding_state: AllocDecodingState::new(footer.interpret_alloc_index),
         }
     }
@@ -151,7 +151,7 @@ impl<'sess> OnDiskCache<'sess> {
             current_diagnostics: Default::default(),
             query_result_index: Default::default(),
             prev_diagnostics_index: Default::default(),
-            synthetic_expansion_infos: Default::default(),
+            synthetic_syntax_contexts: Default::default(),
             alloc_decoding_state: AllocDecodingState::new(Vec::new()),
         }
     }
@@ -185,7 +185,7 @@ impl<'sess> OnDiskCache<'sess> {
                 encoder,
                 type_shorthands: Default::default(),
                 predicate_shorthands: Default::default(),
-                expn_info_shorthands: Default::default(),
+                expn_data_shorthands: Default::default(),
                 interpret_allocs: Default::default(),
                 interpret_allocs_inverse: Vec::new(),
                 source_map: CachingSourceMapView::new(tcx.sess.source_map()),
@@ -383,7 +383,7 @@ impl<'sess> OnDiskCache<'sess> {
             cnum_map: self.cnum_map.get(),
             file_index_to_file: &self.file_index_to_file,
             file_index_to_stable_id: &self.file_index_to_stable_id,
-            synthetic_expansion_infos: &self.synthetic_expansion_infos,
+            synthetic_syntax_contexts: &self.synthetic_syntax_contexts,
             alloc_decoding_session: self.alloc_decoding_state.new_decoding_session(),
         };
 
@@ -440,7 +440,7 @@ struct CacheDecoder<'a, 'tcx> {
     opaque: opaque::Decoder<'a>,
     source_map: &'a SourceMap,
     cnum_map: &'a IndexVec<CrateNum, Option<CrateNum>>,
-    synthetic_expansion_infos: &'a Lock<FxHashMap<AbsoluteBytePos, SyntaxContext>>,
+    synthetic_syntax_contexts: &'a Lock<FxHashMap<AbsoluteBytePos, SyntaxContext>>,
     file_index_to_file: &'a Lock<FxHashMap<SourceFileIndex, Lrc<SourceFile>>>,
     file_index_to_stable_id: &'a FxHashMap<SourceFileIndex, StableSourceFileId>,
     alloc_decoding_session: AllocDecodingSession<'a>,
@@ -586,37 +586,37 @@ impl<'a, 'tcx> SpecializedDecoder<Span> for CacheDecoder<'a, 'tcx> {
         let lo = file_lo.lines[line_lo - 1] + col_lo;
         let hi = lo + len;
 
-        let expn_info_tag = u8::decode(self)?;
+        let expn_data_tag = u8::decode(self)?;
 
-        // FIXME(mw): This method does not restore `InternalExpnData::parent` or
+        // FIXME(mw): This method does not restore `ExpnData::parent` or
         // `SyntaxContextData::prev_ctxt` or `SyntaxContextData::opaque`. These things
         // don't seem to be used after HIR lowering, so everything should be fine
         // as long as incremental compilation does not kick in before that.
-        let location = || Span::new(lo, hi, SyntaxContext::empty());
+        let location = || Span::with_root_ctxt(lo, hi);
-        let recover_from_expn_info = |this: &Self, expn_info, pos| {
+        let recover_from_expn_data = |this: &Self, expn_data, pos| {
-            let span = location().fresh_expansion(ExpnId::root(), expn_info);
+            let span = location().fresh_expansion(expn_data);
-            this.synthetic_expansion_infos.borrow_mut().insert(pos, span.ctxt());
+            this.synthetic_syntax_contexts.borrow_mut().insert(pos, span.ctxt());
             span
         };
-        Ok(match expn_info_tag {
+        Ok(match expn_data_tag {
-            TAG_NO_EXPANSION_INFO => {
+            TAG_NO_EXPN_DATA => {
                 location()
             }
-            TAG_EXPANSION_INFO_INLINE => {
+            TAG_EXPN_DATA_INLINE => {
-                let expn_info = Decodable::decode(self)?;
+                let expn_data = Decodable::decode(self)?;
-                recover_from_expn_info(
+                recover_from_expn_data(
-                    self, expn_info, AbsoluteBytePos::new(self.opaque.position())
+                    self, expn_data, AbsoluteBytePos::new(self.opaque.position())
                 )
             }
-            TAG_EXPANSION_INFO_SHORTHAND => {
+            TAG_EXPN_DATA_SHORTHAND => {
                 let pos = AbsoluteBytePos::decode(self)?;
-                let cached_ctxt = self.synthetic_expansion_infos.borrow().get(&pos).cloned();
+                let cached_ctxt = self.synthetic_syntax_contexts.borrow().get(&pos).cloned();
                 if let Some(ctxt) = cached_ctxt {
                     Span::new(lo, hi, ctxt)
                 } else {
-                    let expn_info =
+                    let expn_data =
-                        self.with_position(pos.to_usize(), |this| ExpnInfo::decode(this))?;
+                        self.with_position(pos.to_usize(), |this| ExpnData::decode(this))?;
-                    recover_from_expn_info(self, expn_info, pos)
+                    recover_from_expn_data(self, expn_data, pos)
                 }
             }
             _ => {
@@ -725,7 +725,7 @@ struct CacheEncoder<'a, 'tcx, E: ty_codec::TyEncoder> {
     encoder: &'a mut E,
     type_shorthands: FxHashMap<Ty<'tcx>, usize>,
     predicate_shorthands: FxHashMap<ty::Predicate<'tcx>, usize>,
-    expn_info_shorthands: FxHashMap<ExpnId, AbsoluteBytePos>,
+    expn_data_shorthands: FxHashMap<ExpnId, AbsoluteBytePos>,
     interpret_allocs: FxHashMap<interpret::AllocId, usize>,
     interpret_allocs_inverse: Vec<interpret::AllocId>,
     source_map: CachingSourceMapView<'tcx>,
@@ -816,22 +816,18 @@ where
         col_lo.encode(self)?;
         len.encode(self)?;
 
-        if span_data.ctxt == SyntaxContext::empty() {
+        if span_data.ctxt == SyntaxContext::root() {
-            TAG_NO_EXPANSION_INFO.encode(self)
+            TAG_NO_EXPN_DATA.encode(self)
         } else {
-            let (expn_id, expn_info) = span_data.ctxt.outer_expn_with_info();
+            let (expn_id, expn_data) = span_data.ctxt.outer_expn_with_data();
-            if let Some(expn_info) = expn_info {
+            if let Some(pos) = self.expn_data_shorthands.get(&expn_id).cloned() {
-                if let Some(pos) = self.expn_info_shorthands.get(&expn_id).cloned() {
+                TAG_EXPN_DATA_SHORTHAND.encode(self)?;
-                    TAG_EXPANSION_INFO_SHORTHAND.encode(self)?;
+                pos.encode(self)
-                    pos.encode(self)
-                } else {
-                    TAG_EXPANSION_INFO_INLINE.encode(self)?;
-                    let pos = AbsoluteBytePos::new(self.position());
-                    self.expn_info_shorthands.insert(expn_id, pos);
-                    expn_info.encode(self)
-                }
             } else {
-                TAG_NO_EXPANSION_INFO.encode(self)
+                TAG_EXPN_DATA_INLINE.encode(self)?;
+                let pos = AbsoluteBytePos::new(self.position());
+                self.expn_data_shorthands.insert(expn_id, pos);
+                expn_data.encode(self)
             }
         }
     }

src/librustc_codegen_ssa/back/write.rs

@@ -1775,10 +1775,7 @@ impl SharedEmitterMain {
                     }
                 }
                 Ok(SharedEmitterMessage::InlineAsmError(cookie, msg)) => {
-                    match ExpnId::from_u32(cookie).expn_info() {
+                    sess.span_err(ExpnId::from_u32(cookie).expn_data().call_site, &msg)
-                        Some(ei) => sess.span_err(ei.call_site, &msg),
-                        None     => sess.err(&msg),
-                    }
                 }
                 Ok(SharedEmitterMessage::AbortIfErrors) => {
                     sess.abort_if_errors();

src/librustc_codegen_ssa/mir/mod.rs

@@ -8,7 +8,7 @@ use crate::base;
 use crate::debuginfo::{self, VariableAccess, VariableKind, FunctionDebugContext};
 use crate::traits::*;
 
-use syntax_pos::{DUMMY_SP, NO_EXPANSION, BytePos, Span};
+use syntax_pos::{DUMMY_SP, BytePos, Span};
 use syntax::symbol::kw;
 
 use std::iter;
@@ -120,7 +120,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         // In order to have a good line stepping behavior in debugger, we overwrite debug
         // locations of macro expansions with that of the outermost expansion site
         // (unless the crate is being compiled with `-Z debug-macros`).
-        if source_info.span.ctxt() == NO_EXPANSION ||
+        if !source_info.span.from_expansion() ||
            self.cx.sess().opts.debugging_opts.debug_macros {
             let scope = self.scope_metadata_for_loc(source_info.scope, source_info.span.lo());
             (scope, source_info.span)

src/librustc_driver/lib.rs

@@ -678,7 +678,7 @@ impl RustcDefaultCalls {
 
                     let mut cfgs = sess.parse_sess.config.iter().filter_map(|&(name, ref value)| {
                         let gated_cfg = GatedCfg::gate(&ast::MetaItem {
-                            path: ast::Path::from_ident(ast::Ident::with_empty_ctxt(name)),
+                            path: ast::Path::from_ident(ast::Ident::with_dummy_span(name)),
                             node: ast::MetaItemKind::Word,
                             span: DUMMY_SP,
                         });

src/librustc_errors/lib.rs

@@ -43,8 +43,7 @@ use syntax_pos::{BytePos,
                  SourceFile,
                  FileName,
                  MultiSpan,
-                 Span,
+                 Span};
-                 NO_EXPANSION};
 
 /// Indicates the confidence in the correctness of a suggestion.
 ///
@@ -189,7 +188,7 @@ impl CodeSuggestion {
             // Find the bounding span.
             let lo = substitution.parts.iter().map(|part| part.span.lo()).min().unwrap();
             let hi = substitution.parts.iter().map(|part| part.span.hi()).min().unwrap();
-            let bounding_span = Span::new(lo, hi, NO_EXPANSION);
+            let bounding_span = Span::with_root_ctxt(lo, hi);
             let lines = cm.span_to_lines(bounding_span).unwrap();
             assert!(!lines.lines.is_empty());
 

src/librustc_lint/builtin.rs

@@ -42,7 +42,7 @@ use syntax::source_map::Spanned;
 use syntax::edition::Edition;
 use syntax::feature_gate::{self, AttributeGate, AttributeType};
 use syntax::feature_gate::{Stability, deprecated_attributes};
-use syntax_pos::{BytePos, Span, SyntaxContext};
+use syntax_pos::{BytePos, Span};
 use syntax::symbol::{Symbol, kw, sym};
 use syntax::errors::{Applicability, DiagnosticBuilder};
 use syntax::print::pprust::expr_to_string;
@@ -78,7 +78,7 @@ impl EarlyLintPass for WhileTrue {
         if let ast::ExprKind::While(cond, ..) = &e.node {
             if let ast::ExprKind::Lit(ref lit) = pierce_parens(cond).node {
                 if let ast::LitKind::Bool(true) = lit.node {
-                    if lit.span.ctxt() == SyntaxContext::empty() {
+                    if !lit.span.from_expansion() {
                         let msg = "denote infinite loops with `loop { ... }`";
                         let condition_span = cx.sess.source_map().def_span(e.span);
                         cx.struct_span_lint(WHILE_TRUE, condition_span, msg)
@@ -167,7 +167,7 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for NonShorthandFieldPatterns {
                 if fieldpat.is_shorthand {
                     continue;
                 }
-                if fieldpat.span.ctxt().outer_expn_info().is_some() {
+                if fieldpat.span.from_expansion() {
                     // Don't lint if this is a macro expansion: macro authors
                     // shouldn't have to worry about this kind of style issue
                     // (Issue #49588)
@@ -1012,7 +1012,7 @@ impl UnreachablePub {
         let mut applicability = Applicability::MachineApplicable;
         match vis.node {
             hir::VisibilityKind::Public if !cx.access_levels.is_reachable(id) => {
-                if span.ctxt().outer_expn_info().is_some() {
+                if span.from_expansion() {
                     applicability = Applicability::MaybeIncorrect;
                 }
                 let def_span = cx.tcx.sess.source_map().def_span(span);

src/librustc_lint/unused.rs

@@ -517,9 +517,8 @@ impl EarlyLintPass for UnusedParens {
                 // trigger in situations that macro authors shouldn't have to care about, e.g.,
                 // when a parenthesized token tree matched in one macro expansion is matched as
                 // an expression in another and used as a fn/method argument (Issue #47775)
-                if e.span.ctxt().outer_expn_info()
+                if e.span.ctxt().outer_expn_data().call_site.from_expansion() {
-                    .map_or(false, |info| info.call_site.ctxt().outer_expn_info().is_some()) {
+                    return;
-                        return;
                 }
                 let msg = format!("{} argument", call_kind);
                 for arg in args_to_check {

src/librustc_metadata/cstore_impl.rs

@@ -35,7 +35,7 @@ use syntax::ext::proc_macro::BangProcMacro;
 use syntax::parse::source_file_to_stream;
 use syntax::parse::parser::emit_unclosed_delims;
 use syntax::symbol::{Symbol, sym};
-use syntax_pos::{Span, NO_EXPANSION, FileName};
+use syntax_pos::{Span, FileName};
 use rustc_data_structures::bit_set::BitSet;
 
 macro_rules! provide {
@@ -443,7 +443,7 @@ impl cstore::CStore {
         let source_name = FileName::Macros(macro_full_name);
 
         let source_file = sess.parse_sess.source_map().new_source_file(source_name, def.body);
-        let local_span = Span::new(source_file.start_pos, source_file.end_pos, NO_EXPANSION);
+        let local_span = Span::with_root_ctxt(source_file.start_pos, source_file.end_pos);
         let (body, mut errors) = source_file_to_stream(&sess.parse_sess, source_file, None);
         emit_unclosed_delims(&mut errors, &sess.diagnostic());
 

src/librustc_metadata/decoder.rs

@@ -32,7 +32,7 @@ use syntax::source_map;
 use syntax::symbol::{Symbol, sym};
 use syntax::ext::base::{MacroKind, SyntaxExtension};
 use syntax::ext::hygiene::ExpnId;
-use syntax_pos::{self, Span, BytePos, Pos, DUMMY_SP, NO_EXPANSION};
+use syntax_pos::{self, Span, BytePos, Pos, DUMMY_SP};
 use log::debug;
 
 pub struct DecodeContext<'a, 'tcx> {
@@ -344,7 +344,7 @@ impl<'a, 'tcx> SpecializedDecoder<Span> for DecodeContext<'a, 'tcx> {
         let hi = (hi + source_file.translated_source_file.start_pos)
                  - source_file.original_start_pos;
 
-        Ok(Span::new(lo, hi, NO_EXPANSION))
+        Ok(Span::with_root_ctxt(lo, hi))
     }
 }
 
@@ -569,7 +569,7 @@ impl<'a, 'tcx> CrateMetadata {
 
         ty::VariantDef::new(
             tcx,
-            Ident::with_empty_ctxt(self.item_name(index)),
+            Ident::with_dummy_span(self.item_name(index)),
             variant_did,
             ctor_did,
             data.discr,
@@ -577,7 +577,7 @@ impl<'a, 'tcx> CrateMetadata {
                 let f = self.entry(index);
                 ty::FieldDef {
                     did: self.local_def_id(index),
-                    ident: Ident::with_empty_ctxt(self.item_name(index)),
+                    ident: Ident::with_dummy_span(self.item_name(index)),
                     vis: f.visibility.decode(self)
                 }
             }).collect(),
@@ -741,7 +741,7 @@ impl<'a, 'tcx> CrateMetadata {
                         DefKind::Macro(ext.macro_kind()),
                         self.local_def_id(DefIndex::from_proc_macro_index(id)),
                     );
-                    let ident = Ident::with_empty_ctxt(name);
+                    let ident = Ident::with_dummy_span(name);
                     callback(def::Export {
                         ident: ident,
                         res: res,
@@ -783,7 +783,7 @@ impl<'a, 'tcx> CrateMetadata {
                             if let Some(kind) = self.def_kind(child_index) {
                                 callback(def::Export {
                                     res: Res::Def(kind, self.local_def_id(child_index)),
-                                    ident: Ident::with_empty_ctxt(self.item_name(child_index)),
+                                    ident: Ident::with_dummy_span(self.item_name(child_index)),
                                     vis: self.get_visibility(child_index),
                                     span: self.entry(child_index).span.decode((self, sess)),
                                 });

src/librustc_resolve/build_reduced_graph.rs

@@ -1,9 +1,11 @@
-//! Reduced graph building.
+//! After we obtain a fresh AST fragment from a macro, code in this module helps to integrate
+//! that fragment into the module structures that are already partially built.
 //!
-//! Here we build the "reduced graph": the graph of the module tree without
+//! Items from the fragment are placed into modules,
-//! any imports resolved.
+//! unexpanded macros in the fragment are visited and registered.
+//! Imports are also considered items and placed into modules here, but not resolved yet.
 
-use crate::macros::{InvocationData, LegacyBinding, LegacyScope};
+use crate::macros::{LegacyBinding, LegacyScope};
 use crate::resolve_imports::ImportDirective;
 use crate::resolve_imports::ImportDirectiveSubclass::{self, GlobImport, SingleImport};
 use crate::{Module, ModuleData, ModuleKind, NameBinding, NameBindingKind, Segment, ToNameBinding};
@@ -30,6 +32,7 @@ use syntax::attr;
 use syntax::ast::{self, Block, ForeignItem, ForeignItemKind, Item, ItemKind, NodeId};
 use syntax::ast::{MetaItemKind, StmtKind, TraitItem, TraitItemKind, Variant};
 use syntax::ext::base::{MacroKind, SyntaxExtension};
+use syntax::ext::expand::AstFragment;
 use syntax::ext::hygiene::ExpnId;
 use syntax::feature_gate::is_builtin_attr;
 use syntax::parse::token::{self, Token};
@@ -67,7 +70,7 @@ impl<'a> ToNameBinding<'a> for (Res, ty::Visibility, Span, ExpnId) {
     }
 }
 
-pub(crate) struct IsMacroExport;
+struct IsMacroExport;
 
 impl<'a> ToNameBinding<'a> for (Res, ty::Visibility, Span, ExpnId, IsMacroExport) {
     fn to_name_binding(self, arenas: &'a ResolverArenas<'a>) -> &'a NameBinding<'a> {
@@ -84,7 +87,7 @@ impl<'a> ToNameBinding<'a> for (Res, ty::Visibility, Span, ExpnId, IsMacroExport
 impl<'a> Resolver<'a> {
     /// Defines `name` in namespace `ns` of module `parent` to be `def` if it is not yet defined;
     /// otherwise, reports an error.
-    pub fn define<T>(&mut self, parent: Module<'a>, ident: Ident, ns: Namespace, def: T)
+    crate fn define<T>(&mut self, parent: Module<'a>, ident: Ident, ns: Namespace, def: T)
         where T: ToNameBinding<'a>,
     {
         let binding = def.to_name_binding(self.arenas);
@@ -93,7 +96,7 @@ impl<'a> Resolver<'a> {
         }
     }
 
-    pub fn get_module(&mut self, def_id: DefId) -> Module<'a> {
+    crate fn get_module(&mut self, def_id: DefId) -> Module<'a> {
         if def_id.krate == LOCAL_CRATE {
             return self.module_map[&def_id]
         }
@@ -119,7 +122,7 @@ impl<'a> Resolver<'a> {
         module
     }
 
-    pub fn macro_def_scope(&mut self, expn_id: ExpnId) -> Module<'a> {
+    crate fn macro_def_scope(&mut self, expn_id: ExpnId) -> Module<'a> {
         let def_id = match self.macro_defs.get(&expn_id) {
             Some(def_id) => *def_id,
             None => return self.graph_root,
@@ -141,7 +144,7 @@ impl<'a> Resolver<'a> {
         }
     }
 
-    crate fn get_macro_by_def_id(&mut self, def_id: DefId) -> Option<Lrc<SyntaxExtension>> {
+    fn get_macro_by_def_id(&mut self, def_id: DefId) -> Option<Lrc<SyntaxExtension>> {
         if let Some(ext) = self.macro_map.get(&def_id) {
             return Some(ext.clone());
         }
@@ -158,21 +161,29 @@ impl<'a> Resolver<'a> {
 
     /// Ensures that the reduced graph rooted at the given external module
     /// is built, building it if it is not.
-    pub fn populate_module_if_necessary(&mut self, module: Module<'a>) {
+    crate fn populate_module_if_necessary(&mut self, module: Module<'a>) {
         if module.populated.get() { return }
         let def_id = module.def_id().unwrap();
         for child in self.cstore.item_children_untracked(def_id, self.session) {
             let child = child.map_id(|_| panic!("unexpected id"));
-            BuildReducedGraphVisitor { parent_scope: self.dummy_parent_scope(), r: self }
+            BuildReducedGraphVisitor { parent_scope: ParentScope::module(module), r: self }
-                .build_reduced_graph_for_external_crate_res(module, child);
+                .build_reduced_graph_for_external_crate_res(child);
         }
         module.populated.set(true)
     }
+
+    crate fn build_reduced_graph(
+        &mut self, fragment: &AstFragment, parent_scope: ParentScope<'a>
+    ) -> LegacyScope<'a> {
+        let mut visitor = BuildReducedGraphVisitor { r: self, parent_scope };
+        fragment.visit_with(&mut visitor);
+        visitor.parent_scope.legacy
+    }
 }
 
-pub struct BuildReducedGraphVisitor<'a, 'b> {
+struct BuildReducedGraphVisitor<'a, 'b> {
-    pub r: &'b mut Resolver<'a>,
+    r: &'b mut Resolver<'a>,
-    pub parent_scope: ParentScope<'a>,
+    parent_scope: ParentScope<'a>,
 }
 
 impl<'a, 'b> BuildReducedGraphVisitor<'a, 'b> {
@@ -300,10 +311,9 @@ impl<'a, 'b> BuildReducedGraphVisitor<'a, 'b> {
         root_id: NodeId,
         vis: ty::Visibility,
     ) {
-        let parent_scope = &self.parent_scope;
+        let current_module = self.parent_scope.module;
-        let current_module = parent_scope.module;
         let directive = self.r.arenas.alloc_import_directive(ImportDirective {
-            parent_scope: parent_scope.clone(),
+            parent_scope: self.parent_scope,
             module_path,
             imported_module: Cell::new(None),
             subclass,
@@ -601,7 +611,7 @@ impl<'a, 'b> BuildReducedGraphVisitor<'a, 'b> {
                 let directive = self.r.arenas.alloc_import_directive(ImportDirective {
                     root_id: item.id,
                     id: item.id,
-                    parent_scope: self.parent_scope.clone(),
+                    parent_scope: self.parent_scope,
                     imported_module: Cell::new(Some(ModuleOrUniformRoot::Module(module))),
                     subclass: ImportDirectiveSubclass::ExternCrate {
                         source: orig_name,
@@ -706,7 +716,7 @@ impl<'a, 'b> BuildReducedGraphVisitor<'a, 'b> {
                 self.r.define(parent, ident, TypeNS, (module, vis, sp, expansion));
 
                 for variant in &(*enum_definition).variants {
-                    self.build_reduced_graph_for_variant(variant, module, vis, expansion);
+                    self.build_reduced_graph_for_variant(variant, module, vis);
                 }
             }
 
@@ -797,8 +807,8 @@ impl<'a, 'b> BuildReducedGraphVisitor<'a, 'b> {
     fn build_reduced_graph_for_variant(&mut self,
                                        variant: &Variant,
                                        parent: Module<'a>,
-                                       vis: ty::Visibility,
+                                       vis: ty::Visibility) {
-                                       expn_id: ExpnId) {
+        let expn_id = self.parent_scope.expansion;
         let ident = variant.ident;
 
         // Define a name in the type namespace.
@@ -861,11 +871,8 @@ impl<'a, 'b> BuildReducedGraphVisitor<'a, 'b> {
     }
 
     /// Builds the reduced graph for a single item in an external crate.
-    fn build_reduced_graph_for_external_crate_res(
+    fn build_reduced_graph_for_external_crate_res(&mut self, child: Export<ast::NodeId>) {
-        &mut self,
+        let parent = self.parent_scope.module;
-        parent: Module<'a>,
-        child: Export<ast::NodeId>,
-    ) {
         let Export { ident, res, vis, span } = child;
         // FIXME: We shouldn't create the gensym here, it should come from metadata,
         // but metadata cannot encode gensyms currently, so we create it here.
@@ -997,7 +1004,7 @@ impl<'a, 'b> BuildReducedGraphVisitor<'a, 'b> {
                 |this: &Self, span| this.r.arenas.alloc_import_directive(ImportDirective {
             root_id: item.id,
             id: item.id,
-            parent_scope: this.parent_scope.clone(),
+            parent_scope: this.parent_scope,
             imported_module: Cell::new(Some(ModuleOrUniformRoot::Module(module))),
             subclass: ImportDirectiveSubclass::MacroUse,
             use_span_with_attributes: item.span_with_attributes(),
@@ -1066,20 +1073,15 @@ impl<'a, 'b> BuildReducedGraphVisitor<'a, 'b> {
         false
     }
 
-    fn visit_invoc(&mut self, id: ast::NodeId) -> &'a InvocationData<'a> {
+    fn visit_invoc(&mut self, id: ast::NodeId) -> LegacyScope<'a> {
         let invoc_id = id.placeholder_to_expn_id();
 
         self.parent_scope.module.unresolved_invocations.borrow_mut().insert(invoc_id);
 
-        let invocation_data = self.r.arenas.alloc_invocation_data(InvocationData {
+        let old_parent_scope = self.r.invocation_parent_scopes.insert(invoc_id, self.parent_scope);
-            module: self.parent_scope.module,
+        assert!(old_parent_scope.is_none(), "invocation data is reset for an invocation");
-            parent_legacy_scope: self.parent_scope.legacy,
-            output_legacy_scope: Cell::new(None),
-        });
-        let old_invocation_data = self.r.invocations.insert(invoc_id, invocation_data);
-        assert!(old_invocation_data.is_none(), "invocation data is reset for an invocation");
 
-        invocation_data
+        LegacyScope::Invocation(invoc_id)
     }
 
     fn proc_macro_stub(item: &ast::Item) -> Option<(MacroKind, Ident, Span)> {
@@ -1180,7 +1182,7 @@ impl<'a, 'b> Visitor<'b> for BuildReducedGraphVisitor<'a, 'b> {
                 return
             }
             ItemKind::Mac(..) => {
-                self.parent_scope.legacy = LegacyScope::Invocation(self.visit_invoc(item.id));
+                self.parent_scope.legacy = self.visit_invoc(item.id);
                 return
             }
             ItemKind::Mod(..) => self.contains_macro_use(&item.attrs),
@@ -1199,7 +1201,7 @@ impl<'a, 'b> Visitor<'b> for BuildReducedGraphVisitor<'a, 'b> {
 
     fn visit_stmt(&mut self, stmt: &'b ast::Stmt) {
         if let ast::StmtKind::Mac(..) = stmt.node {
-            self.parent_scope.legacy = LegacyScope::Invocation(self.visit_invoc(stmt.id));
+            self.parent_scope.legacy = self.visit_invoc(stmt.id);
         } else {
             visit::walk_stmt(self, stmt);
         }
@@ -1267,9 +1269,7 @@ impl<'a, 'b> Visitor<'b> for BuildReducedGraphVisitor<'a, 'b> {
 
     fn visit_attribute(&mut self, attr: &'b ast::Attribute) {
         if !attr.is_sugared_doc && is_builtin_attr(attr) {
-            self.parent_scope.module.builtin_attrs.borrow_mut().push((
+            self.r.builtin_attrs.push((attr.path.segments[0].ident, self.parent_scope));
-                attr.path.segments[0].ident, self.parent_scope.clone()
-            ));
         }
         visit::walk_attribute(self, attr);
     }

src/librustc_resolve/diagnostics.rs

@@ -376,9 +376,9 @@ impl<'a> Resolver<'a> {
                 Scope::DeriveHelpers => {
                     let res = Res::NonMacroAttr(NonMacroAttrKind::DeriveHelper);
                     if filter_fn(res) {
-                        for derive in &parent_scope.derives {
+                        for derive in parent_scope.derives {
                             let parent_scope =
-                                &ParentScope { derives: Vec::new(), ..*parent_scope };
+                                &ParentScope { derives: &[], ..*parent_scope };
                             if let Ok((Some(ext), _)) = this.resolve_macro_path(
                                 derive, Some(MacroKind::Derive), parent_scope, false, false
                             ) {
@@ -455,7 +455,7 @@ impl<'a> Resolver<'a> {
                         let mut tmp_suggestions = Vec::new();
                         add_module_candidates(prelude, &mut tmp_suggestions, filter_fn);
                         suggestions.extend(tmp_suggestions.into_iter().filter(|s| {
-                            use_prelude || this.is_builtin_macro(s.res.opt_def_id())
+                            use_prelude || this.is_builtin_macro(s.res)
                         }));
                     }
                 }
@@ -595,7 +595,7 @@ impl<'a> Resolver<'a> {
         where FilterFn: Fn(Res) -> bool
     {
         let mut suggestions = self.lookup_import_candidates_from_module(
-            lookup_ident, namespace, self.graph_root, Ident::with_empty_ctxt(kw::Crate), &filter_fn
+            lookup_ident, namespace, self.graph_root, Ident::with_dummy_span(kw::Crate), &filter_fn
         );
 
         if lookup_ident.span.rust_2018() {

src/librustc_resolve/late.rs

@@ -1,3 +1,10 @@
+//! "Late resolution" is the pass that resolves most of names in a crate beside imports and macros.
+//! It runs when the crate is fully expanded and its module structure is fully built.
+//! So it just walks through the crate and resolves all the expressions, types, etc.
+//!
+//! If you wonder why there's no `early.rs`, that's because it's split into three files -
+//! `build_reduced_graph.rs`, `macros.rs` and `resolve_imports.rs`.
+
 use GenericParameters::*;
 use RibKind::*;
 
@@ -352,7 +359,7 @@ impl<'a, 'tcx> Visitor<'tcx> for LateResolutionVisitor<'a, '_> {
                 self.smart_resolve_path(ty.id, qself.as_ref(), path, PathSource::Type);
             }
             TyKind::ImplicitSelf => {
-                let self_ty = Ident::with_empty_ctxt(kw::SelfUpper);
+                let self_ty = Ident::with_dummy_span(kw::SelfUpper);
                 let res = self.resolve_ident_in_lexical_scope(self_ty, TypeNS, Some(ty.id), ty.span)
                               .map_or(Res::Err, |d| d.res());
                 self.r.record_partial_res(ty.id, PartialRes::new(res));
@@ -442,7 +449,7 @@ impl<'a, 'tcx> Visitor<'tcx> for LateResolutionVisitor<'a, '_> {
                 GenericParamKind::Type { ref default, .. } => {
                     found_default |= default.is_some();
                     if found_default {
-                        Some((Ident::with_empty_ctxt(param.ident.name), Res::Err))
+                        Some((Ident::with_dummy_span(param.ident.name), Res::Err))
                     } else {
                         None
                     }
@@ -459,7 +466,7 @@ impl<'a, 'tcx> Visitor<'tcx> for LateResolutionVisitor<'a, '_> {
                     false
                 }
             })
-            .map(|param| (Ident::with_empty_ctxt(param.ident.name), Res::Err)));
+            .map(|param| (Ident::with_dummy_span(param.ident.name), Res::Err)));
 
         for param in &generics.params {
             match param.kind {
@@ -476,7 +483,7 @@ impl<'a, 'tcx> Visitor<'tcx> for LateResolutionVisitor<'a, '_> {
                     }
 
                     // Allow all following defaults to refer to this type parameter.
-                    default_ban_rib.bindings.remove(&Ident::with_empty_ctxt(param.ident.name));
+                    default_ban_rib.bindings.remove(&Ident::with_dummy_span(param.ident.name));
                 }
                 GenericParamKind::Const { ref ty } => {
                     self.ribs[TypeNS].push(const_ty_param_ban_rib);
@@ -501,8 +508,8 @@ impl<'a, 'b> LateResolutionVisitor<'a, '_> {
     fn new(resolver: &'b mut Resolver<'a>) -> LateResolutionVisitor<'a, 'b> {
         // During late resolution we only track the module component of the parent scope,
         // although it may be useful to track other components as well for diagnostics.
-        let parent_scope = resolver.dummy_parent_scope();
         let graph_root = resolver.graph_root;
+        let parent_scope = ParentScope::module(graph_root);
         LateResolutionVisitor {
             r: resolver,
             parent_scope,
@@ -574,7 +581,6 @@ impl<'a, 'b> LateResolutionVisitor<'a, '_> {
             self.ribs[ValueNS].push(Rib::new(ModuleRibKind(module)));
             self.ribs[TypeNS].push(Rib::new(ModuleRibKind(module)));
 
-            self.r.finalize_current_module_macro_resolutions(module);
             let ret = f(self);
 
             self.parent_scope.module = orig_module;
@@ -965,7 +971,7 @@ impl<'a, 'b> LateResolutionVisitor<'a, '_> {
         let mut self_type_rib = Rib::new(NormalRibKind);
 
         // Plain insert (no renaming, since types are not currently hygienic)
-        self_type_rib.bindings.insert(Ident::with_empty_ctxt(kw::SelfUpper), self_res);
+        self_type_rib.bindings.insert(Ident::with_dummy_span(kw::SelfUpper), self_res);
         self.ribs[TypeNS].push(self_type_rib);
         f(self);
         self.ribs[TypeNS].pop();
@@ -976,7 +982,7 @@ impl<'a, 'b> LateResolutionVisitor<'a, '_> {
     {
         let self_res = Res::SelfCtor(impl_id);
         let mut self_type_rib = Rib::new(NormalRibKind);
-        self_type_rib.bindings.insert(Ident::with_empty_ctxt(kw::SelfUpper), self_res);
+        self_type_rib.bindings.insert(Ident::with_dummy_span(kw::SelfUpper), self_res);
         self.ribs[ValueNS].push(self_type_rib);
         f(self);
         self.ribs[ValueNS].pop();
@@ -1227,7 +1233,6 @@ impl<'a, 'b> LateResolutionVisitor<'a, '_> {
             self.ribs[ValueNS].push(Rib::new(ModuleRibKind(anonymous_module)));
             self.ribs[TypeNS].push(Rib::new(ModuleRibKind(anonymous_module)));
             self.parent_scope.module = anonymous_module;
-            self.r.finalize_current_module_macro_resolutions(anonymous_module);
         } else {
             self.ribs[ValueNS].push(Rib::new(NormalRibKind));
         }
@@ -1476,7 +1481,7 @@ impl<'a, 'b> LateResolutionVisitor<'a, '_> {
                     self.r.trait_map.insert(id, traits);
                 }
 
-                let mut std_path = vec![Segment::from_ident(Ident::with_empty_ctxt(sym::std))];
+                let mut std_path = vec![Segment::from_ident(Ident::with_dummy_span(sym::std))];
                 std_path.extend(path);
                 if self.r.primitive_type_table.primitive_types.contains_key(&path[0].ident.name) {
                     let cl = CrateLint::No;
@@ -1507,7 +1512,7 @@ impl<'a, 'b> LateResolutionVisitor<'a, '_> {
 
     fn self_type_is_available(&mut self, span: Span) -> bool {
         let binding = self.resolve_ident_in_lexical_scope(
-            Ident::with_empty_ctxt(kw::SelfUpper),
+            Ident::with_dummy_span(kw::SelfUpper),
             TypeNS,
             None,
             span,
@@ -1984,7 +1989,6 @@ impl<'a, 'b> LateResolutionVisitor<'a, '_> {
 
 impl<'a> Resolver<'a> {
     pub(crate) fn late_resolve_crate(&mut self, krate: &Crate) {
-        self.finalize_current_module_macro_resolutions(self.graph_root);
         let mut late_resolution_visitor = LateResolutionVisitor::new(self);
         visit::walk_crate(&mut late_resolution_visitor, krate);
         for (id, span) in late_resolution_visitor.unused_labels.iter() {

src/librustc_resolve/lib.rs

@@ -1,3 +1,12 @@
+//! This crate is responsible for the part of name resolution that doesn't require type checker.
+//!
+//! Module structure of the crate is built here.
+//! Paths in macros, imports, expressions, types, patterns are resolved here.
+//! Label names are resolved here as well.
+//!
+//! Type-relative name resolution (methods, fields, associated items) happens in `librustc_typeck`.
+//! Lifetime names are resolved in `librustc/middle/resolve_lifetime.rs`.
+
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/")]
 
 #![feature(crate_visibility_modifier)]
@@ -54,7 +63,7 @@ use diagnostics::{Suggestion, ImportSuggestion};
 use diagnostics::{find_span_of_binding_until_next_binding, extend_span_to_previous_binding};
 use late::{PathSource, Rib, RibKind::*};
 use resolve_imports::{ImportDirective, ImportDirectiveSubclass, NameResolution, ImportResolver};
-use macros::{InvocationData, LegacyBinding, LegacyScope};
+use macros::{LegacyBinding, LegacyScope};
 
 type Res = def::Res<NodeId>;
 
@@ -122,12 +131,25 @@ enum ScopeSet {
 /// Serves as a starting point for the scope visitor.
 /// This struct is currently used only for early resolution (imports and macros),
 /// but not for late resolution yet.
-#[derive(Clone, Debug)]
+#[derive(Clone, Copy, Debug)]
 pub struct ParentScope<'a> {
     module: Module<'a>,
     expansion: ExpnId,
     legacy: LegacyScope<'a>,
-    derives: Vec<ast::Path>,
+    derives: &'a [ast::Path],
+}
+
+impl<'a> ParentScope<'a> {
+    /// Creates a parent scope with the passed argument used as the module scope component,
+    /// and other scope components set to default empty values.
+    pub fn module(module: Module<'a>) -> ParentScope<'a> {
+        ParentScope {
+            module,
+            expansion: ExpnId::root(),
+            legacy: LegacyScope::Empty,
+            derives: &[],
+        }
+    }
 }
 
 #[derive(Eq)]
@@ -274,7 +296,7 @@ impl<'tcx> Visitor<'tcx> for UsePlacementFinder {
                 ItemKind::Use(..) => {
                     // don't suggest placing a use before the prelude
                     // import or other generated ones
-                    if item.span.ctxt().outer_expn_info().is_none() {
+                    if !item.span.from_expansion() {
                         self.span = Some(item.span.shrink_to_lo());
                         self.found_use = true;
                         return;
@@ -284,7 +306,7 @@ impl<'tcx> Visitor<'tcx> for UsePlacementFinder {
                 ItemKind::ExternCrate(_) => {}
                 // but place them before the first other item
                 _ => if self.span.map_or(true, |span| item.span < span ) {
-                    if item.span.ctxt().outer_expn_info().is_none() {
+                    if !item.span.from_expansion() {
                         // don't insert between attributes and an item
                         if item.attrs.is_empty() {
                             self.span = Some(item.span.shrink_to_lo());
@@ -418,11 +440,6 @@ pub struct ModuleData<'a> {
     normal_ancestor_id: DefId,
 
     resolutions: RefCell<FxHashMap<(Ident, Namespace), &'a RefCell<NameResolution<'a>>>>,
-    single_segment_macro_resolutions: RefCell<Vec<(Ident, MacroKind, ParentScope<'a>,
-                                                   Option<&'a NameBinding<'a>>)>>,
-    multi_segment_macro_resolutions: RefCell<Vec<(Vec<Segment>, Span, MacroKind, ParentScope<'a>,
-                                                  Option<Res>)>>,
-    builtin_attrs: RefCell<Vec<(Ident, ParentScope<'a>)>>,
 
     // Macro invocations that can expand into items in this module.
     unresolved_invocations: RefCell<FxHashSet<ExpnId>>,
@@ -459,9 +476,6 @@ impl<'a> ModuleData<'a> {
             kind,
             normal_ancestor_id,
             resolutions: Default::default(),
-            single_segment_macro_resolutions: RefCell::new(Vec::new()),
-            multi_segment_macro_resolutions: RefCell::new(Vec::new()),
-            builtin_attrs: RefCell::new(Vec::new()),
             unresolved_invocations: Default::default(),
             no_implicit_prelude: false,
             glob_importers: RefCell::new(Vec::new()),
@@ -807,7 +821,7 @@ pub struct Resolver<'a> {
 
     pub definitions: Definitions,
 
-    graph_root: Module<'a>,
+    pub graph_root: Module<'a>,
 
     prelude: Option<Module<'a>>,
     pub extern_prelude: FxHashMap<Ident, ExternPreludeEntry<'a>>,
@@ -896,15 +910,24 @@ pub struct Resolver<'a> {
     local_macro_def_scopes: FxHashMap<NodeId, Module<'a>>,
     unused_macros: NodeMap<Span>,
     proc_macro_stubs: NodeSet,
+    /// Traces collected during macro resolution and validated when it's complete.
+    single_segment_macro_resolutions: Vec<(Ident, MacroKind, ParentScope<'a>,
+                                           Option<&'a NameBinding<'a>>)>,
+    multi_segment_macro_resolutions: Vec<(Vec<Segment>, Span, MacroKind, ParentScope<'a>,
+                                          Option<Res>)>,
+    builtin_attrs: Vec<(Ident, ParentScope<'a>)>,
     /// Some built-in derives mark items they are applied to so they are treated specially later.
     /// Derive macros cannot modify the item themselves and have to store the markers in the global
     /// context, so they attach the markers to derive container IDs using this resolver table.
     /// FIXME: Find a way for `PartialEq` and `Eq` to emulate `#[structural_match]`
     /// by marking the produced impls rather than the original items.
     special_derives: FxHashMap<ExpnId, SpecialDerives>,
-
+    /// Parent scopes in which the macros were invoked.
-    /// Maps the `ExpnId` of an expansion to its containing module or block.
+    /// FIXME: `derives` are missing in these parent scopes and need to be taken from elsewhere.
-    invocations: FxHashMap<ExpnId, &'a InvocationData<'a>>,
+    invocation_parent_scopes: FxHashMap<ExpnId, ParentScope<'a>>,
+    /// Legacy scopes *produced* by expanding the macro invocations,
+    /// include all the `macro_rules` items and other invocations generated by them.
+    output_legacy_scopes: FxHashMap<ExpnId, LegacyScope<'a>>,
 
     /// Avoid duplicated errors for "name already defined".
     name_already_seen: FxHashMap<Name, Span>,
@@ -927,8 +950,8 @@ pub struct ResolverArenas<'a> {
     name_bindings: arena::TypedArena<NameBinding<'a>>,
     import_directives: arena::TypedArena<ImportDirective<'a>>,
     name_resolutions: arena::TypedArena<RefCell<NameResolution<'a>>>,
-    invocation_data: arena::TypedArena<InvocationData<'a>>,
     legacy_bindings: arena::TypedArena<LegacyBinding<'a>>,
+    ast_paths: arena::TypedArena<ast::Path>,
 }
 
 impl<'a> ResolverArenas<'a> {
@@ -952,13 +975,12 @@ impl<'a> ResolverArenas<'a> {
     fn alloc_name_resolution(&'a self) -> &'a RefCell<NameResolution<'a>> {
         self.name_resolutions.alloc(Default::default())
     }
-    fn alloc_invocation_data(&'a self, expansion_data: InvocationData<'a>)
-                             -> &'a InvocationData<'a> {
-        self.invocation_data.alloc(expansion_data)
-    }
     fn alloc_legacy_binding(&'a self, binding: LegacyBinding<'a>) -> &'a LegacyBinding<'a> {
         self.legacy_bindings.alloc(binding)
     }
+    fn alloc_ast_paths(&'a self, paths: &[ast::Path]) -> &'a [ast::Path] {
+        self.ast_paths.alloc_from_iter(paths.iter().cloned())
+    }
 }
 
 impl<'a, 'b> ty::DefIdTree for &'a Resolver<'b> {
@@ -985,11 +1007,11 @@ impl<'a> hir::lowering::Resolver for Resolver<'a> {
         } else {
             kw::Crate
         };
-        let segments = iter::once(Ident::with_empty_ctxt(root))
+        let segments = iter::once(Ident::with_dummy_span(root))
             .chain(
                 crate_root.into_iter()
                     .chain(components.iter().cloned())
-                    .map(Ident::with_empty_ctxt)
+                    .map(Ident::with_dummy_span)
             ).map(|i| self.new_ast_path_segment(i)).collect::<Vec<_>>();
 
         let path = ast::Path {
@@ -997,7 +1019,7 @@ impl<'a> hir::lowering::Resolver for Resolver<'a> {
             segments,
         };
 
-        let parent_scope = &self.dummy_parent_scope();
+        let parent_scope = &ParentScope::module(self.graph_root);
         let res = match self.resolve_ast_path(&path, ns, parent_scope) {
             Ok(res) => res,
             Err((span, error)) => {
@@ -1060,18 +1082,17 @@ impl<'a> Resolver<'a> {
                                        .collect();
 
         if !attr::contains_name(&krate.attrs, sym::no_core) {
-            extern_prelude.insert(Ident::with_empty_ctxt(sym::core), Default::default());
+            extern_prelude.insert(Ident::with_dummy_span(sym::core), Default::default());
             if !attr::contains_name(&krate.attrs, sym::no_std) {
-                extern_prelude.insert(Ident::with_empty_ctxt(sym::std), Default::default());
+                extern_prelude.insert(Ident::with_dummy_span(sym::std), Default::default());
                 if session.rust_2018() {
-                    extern_prelude.insert(Ident::with_empty_ctxt(sym::meta), Default::default());
+                    extern_prelude.insert(Ident::with_dummy_span(sym::meta), Default::default());
                 }
             }
         }
 
-        let mut invocations = FxHashMap::default();
+        let mut invocation_parent_scopes = FxHashMap::default();
-        invocations.insert(ExpnId::root(),
+        invocation_parent_scopes.insert(ExpnId::root(), ParentScope::module(graph_root));
-                           arenas.alloc_invocation_data(InvocationData::root(graph_root)));
 
         let mut macro_defs = FxHashMap::default();
         macro_defs.insert(ExpnId::root(), root_def_id);
@@ -1143,7 +1164,8 @@ impl<'a> Resolver<'a> {
             dummy_ext_bang: Lrc::new(SyntaxExtension::dummy_bang(session.edition())),
             dummy_ext_derive: Lrc::new(SyntaxExtension::dummy_derive(session.edition())),
             non_macro_attrs: [non_macro_attr(false), non_macro_attr(true)],
-            invocations,
+            invocation_parent_scopes,
+            output_legacy_scopes: Default::default(),
             macro_defs,
             local_macro_def_scopes: FxHashMap::default(),
             name_already_seen: FxHashMap::default(),
@@ -1151,6 +1173,9 @@ impl<'a> Resolver<'a> {
             struct_constructors: Default::default(),
             unused_macros: Default::default(),
             proc_macro_stubs: Default::default(),
+            single_segment_macro_resolutions: Default::default(),
+            multi_segment_macro_resolutions: Default::default(),
+            builtin_attrs: Default::default(),
             special_derives: Default::default(),
             active_features:
                 features.declared_lib_features.iter().map(|(feat, ..)| *feat)
@@ -1182,9 +1207,8 @@ impl<'a> Resolver<'a> {
         f(self, MacroNS);
     }
 
-    fn is_builtin_macro(&mut self, def_id: Option<DefId>) -> bool {
+    fn is_builtin_macro(&mut self, res: Res) -> bool {
-        def_id.and_then(|def_id| self.get_macro_by_def_id(def_id))
+        self.get_macro(res).map_or(false, |ext| ext.is_builtin)
-              .map_or(false, |ext| ext.is_builtin)
     }
 
     fn macro_def(&self, mut ctxt: SyntaxContext) -> DefId {
@@ -1203,6 +1227,7 @@ impl<'a> Resolver<'a> {
     /// Entry point to crate resolution.
     pub fn resolve_crate(&mut self, krate: &Crate) {
         ImportResolver { r: self }.finalize_imports();
+        self.finalize_macro_resolutions();
 
         self.late_resolve_crate(krate);
 
@@ -1319,13 +1344,15 @@ impl<'a> Resolver<'a> {
             ScopeSet::AbsolutePath(ns) => (ns, true),
             ScopeSet::Macro(_) => (MacroNS, false),
         };
+        // Jump out of trait or enum modules, they do not act as scopes.
+        let module = parent_scope.module.nearest_item_scope();
         let mut scope = match ns {
             _ if is_absolute_path => Scope::CrateRoot,
-            TypeNS | ValueNS => Scope::Module(parent_scope.module),
+            TypeNS | ValueNS => Scope::Module(module),
             MacroNS => Scope::DeriveHelpers,
         };
         let mut ident = ident.modern();
-        let mut use_prelude = !parent_scope.module.no_implicit_prelude;
+        let mut use_prelude = !module.no_implicit_prelude;
 
         loop {
             let visit = match scope {
@@ -1355,10 +1382,11 @@ impl<'a> Resolver<'a> {
                     LegacyScope::Binding(binding) => Scope::MacroRules(
                         binding.parent_legacy_scope
                     ),
-                    LegacyScope::Invocation(invoc) => Scope::MacroRules(
+                    LegacyScope::Invocation(invoc_id) => Scope::MacroRules(
-                        invoc.output_legacy_scope.get().unwrap_or(invoc.parent_legacy_scope)
+                        self.output_legacy_scopes.get(&invoc_id).cloned()
+                            .unwrap_or(self.invocation_parent_scopes[&invoc_id].legacy)
                     ),
-                    LegacyScope::Empty => Scope::Module(parent_scope.module),
+                    LegacyScope::Empty => Scope::Module(module),
                 }
                 Scope::CrateRoot => match ns {
                     TypeNS => {
@@ -1430,7 +1458,7 @@ impl<'a> Resolver<'a> {
         }
         let (general_span, modern_span) = if ident.name == kw::SelfUpper {
             // FIXME(jseyfried) improve `Self` hygiene
-            let empty_span = ident.span.with_ctxt(SyntaxContext::empty());
+            let empty_span = ident.span.with_ctxt(SyntaxContext::root());
             (empty_span, empty_span)
         } else if ns == TypeNS {
             let modern_span = ident.span.modern();
@@ -1501,7 +1529,7 @@ impl<'a> Resolver<'a> {
                 self.hygienic_lexical_parent(module, &mut ident.span)
             };
             module = unwrap_or!(opt_module, break);
-            let adjusted_parent_scope = &ParentScope { module, ..parent_scope.clone() };
+            let adjusted_parent_scope = &ParentScope { module, ..*parent_scope };
             let result = self.resolve_ident_in_module_unadjusted(
                 ModuleOrUniformRoot::Module(module),
                 ident,
@@ -1637,7 +1665,7 @@ impl<'a> Resolver<'a> {
             ModuleOrUniformRoot::Module(m) => {
                 if let Some(def) = ident.span.modernize_and_adjust(m.expansion) {
                     tmp_parent_scope =
-                        ParentScope { module: self.macro_def_scope(def), ..parent_scope.clone() };
+                        ParentScope { module: self.macro_def_scope(def), ..*parent_scope };
                     adjusted_parent_scope = &tmp_parent_scope;
                 }
             }
@@ -2624,7 +2652,7 @@ impl<'a> Resolver<'a> {
         let path = if path_str.starts_with("::") {
             ast::Path {
                 span,
-                segments: iter::once(Ident::with_empty_ctxt(kw::PathRoot))
+                segments: iter::once(Ident::with_dummy_span(kw::PathRoot))
                     .chain({
                         path_str.split("::").skip(1).map(Ident::from_str)
                     })
@@ -2645,7 +2673,7 @@ impl<'a> Resolver<'a> {
             let def_id = self.definitions.local_def_id(module_id);
             self.module_map.get(&def_id).copied().unwrap_or(self.graph_root)
         });
-        let parent_scope = &ParentScope { module, ..self.dummy_parent_scope() };
+        let parent_scope = &ParentScope::module(module);
         let res = self.resolve_ast_path(&path, ns, parent_scope).map_err(|_| ())?;
         Ok((path, res))
     }
@@ -2713,7 +2741,7 @@ fn module_to_string(module: Module<'_>) -> Option<String> {
     fn collect_mod(names: &mut Vec<Ident>, module: Module<'_>) {
         if let ModuleKind::Def(.., name) = module.kind {
             if let Some(parent) = module.parent {
-                names.push(Ident::with_empty_ctxt(name));
+                names.push(Ident::with_dummy_span(name));
                 collect_mod(names, parent);
             }
         } else {

src/librustc_resolve/macros.rs

@@ -1,9 +1,11 @@
+//! A bunch of methods and structures more or less related to resolving macros and
+//! interface provided by `Resolver` to macro expander.
+
 use crate::{AmbiguityError, AmbiguityKind, AmbiguityErrorMisc, Determinacy};
 use crate::{CrateLint, Resolver, ResolutionError, Scope, ScopeSet, ParentScope, Weak};
-use crate::{Module, ModuleKind, NameBinding, PathResult, Segment, ToNameBinding};
+use crate::{ModuleKind, NameBinding, PathResult, Segment, ToNameBinding};
 use crate::{ModuleOrUniformRoot, KNOWN_TOOLS};
 use crate::Namespace::*;
-use crate::build_reduced_graph::BuildReducedGraphVisitor;
 use crate::resolve_imports::ImportResolver;
 use rustc::hir::def::{self, DefKind, NonMacroAttrKind};
 use rustc::hir::map::DefCollector;
@@ -15,43 +17,18 @@ use syntax::edition::Edition;
 use syntax::ext::base::{self, Indeterminate, SpecialDerives};
 use syntax::ext::base::{MacroKind, SyntaxExtension};
 use syntax::ext::expand::{AstFragment, Invocation, InvocationKind};
-use syntax::ext::hygiene::{self, ExpnId, ExpnInfo, ExpnKind};
+use syntax::ext::hygiene::{self, ExpnId, ExpnData, ExpnKind};
 use syntax::ext::tt::macro_rules;
 use syntax::feature_gate::{emit_feature_err, is_builtin_attr_name};
 use syntax::feature_gate::GateIssue;
 use syntax::symbol::{Symbol, kw, sym};
 use syntax_pos::{Span, DUMMY_SP};
 
-use std::cell::Cell;
 use std::{mem, ptr};
 use rustc_data_structures::sync::Lrc;
 
 type Res = def::Res<ast::NodeId>;
 
-// FIXME: Merge this with `ParentScope`.
-#[derive(Clone, Debug)]
-pub struct InvocationData<'a> {
-    /// The module in which the macro was invoked.
-    crate module: Module<'a>,
-    /// The legacy scope in which the macro was invoked.
-    /// The invocation path is resolved in this scope.
-    crate parent_legacy_scope: LegacyScope<'a>,
-    /// The legacy scope *produced* by expanding this macro invocation,
-    /// includes all the macro_rules items, other invocations, etc generated by it.
-    /// `None` if the macro is not expanded yet.
-    crate output_legacy_scope: Cell<Option<LegacyScope<'a>>>,
-}
-
-impl<'a> InvocationData<'a> {
-    pub fn root(graph_root: Module<'a>) -> Self {
-        InvocationData {
-            module: graph_root,
-            parent_legacy_scope: LegacyScope::Empty,
-            output_legacy_scope: Cell::new(None),
-        }
-    }
-}
-
 /// Binding produced by a `macro_rules` item.
 /// Not modularized, can shadow previous legacy bindings, etc.
 #[derive(Debug)]
@@ -75,7 +52,7 @@ pub enum LegacyScope<'a> {
     Binding(&'a LegacyBinding<'a>),
     /// The scope introduced by a macro invocation that can potentially
     /// create a `macro_rules!` macro definition.
-    Invocation(&'a InvocationData<'a>),
+    Invocation(ExpnId),
 }
 
 // Macro namespace is separated into two sub-namespaces, one for bang macros and
@@ -120,17 +97,12 @@ impl<'a> base::Resolver for Resolver<'a> {
     }
 
     fn get_module_scope(&mut self, id: ast::NodeId) -> ExpnId {
-        let span = DUMMY_SP.fresh_expansion(ExpnId::root(), ExpnInfo::default(
+        let expn_id = ExpnId::fresh(Some(ExpnData::default(
             ExpnKind::Macro(MacroKind::Attr, sym::test_case), DUMMY_SP, self.session.edition()
-        ));
+        )));
-        let expn_id = span.ctxt().outer_expn();
         let module = self.module_map[&self.definitions.local_def_id(id)];
+        self.invocation_parent_scopes.insert(expn_id, ParentScope::module(module));
         self.definitions.set_invocation_parent(expn_id, module.def_id().unwrap().index);
-        self.invocations.insert(expn_id, self.arenas.alloc_invocation_data(InvocationData {
-            module,
-            parent_legacy_scope: LegacyScope::Empty,
-            output_legacy_scope: Cell::new(None),
-        }));
         expn_id
     }
 
@@ -144,29 +116,24 @@ impl<'a> base::Resolver for Resolver<'a> {
         });
     }
 
-    fn visit_ast_fragment_with_placeholders(&mut self, expn_id: ExpnId, fragment: &AstFragment,
+    fn visit_ast_fragment_with_placeholders(
-                                            derives: &[ExpnId]) {
+        &mut self, expansion: ExpnId, fragment: &AstFragment, derives: &[ExpnId]
-        fragment.visit_with(&mut DefCollector::new(&mut self.definitions, expn_id));
+    ) {
-
+        // Fill in some data for derives if the fragment is from a derive container.
-        let invocation = self.invocations[&expn_id];
+        // We are inside the `expansion` now, but other parent scope components are still the same.
-        invocation.module.unresolved_invocations.borrow_mut().remove(&expn_id);
+        let parent_scope = ParentScope { expansion, ..self.invocation_parent_scopes[&expansion] };
-        invocation.module.unresolved_invocations.borrow_mut().extend(derives);
+        let parent_def = self.definitions.invocation_parent(expansion);
-        let parent_def = self.definitions.invocation_parent(expn_id);
+        self.invocation_parent_scopes.extend(derives.iter().map(|&derive| (derive, parent_scope)));
         for &derive_invoc_id in derives {
             self.definitions.set_invocation_parent(derive_invoc_id, parent_def);
         }
-        self.invocations.extend(derives.iter().map(|&derive| (derive, invocation)));
+        parent_scope.module.unresolved_invocations.borrow_mut().remove(&expansion);
-        let mut visitor = BuildReducedGraphVisitor {
+        parent_scope.module.unresolved_invocations.borrow_mut().extend(derives);
-            r: self,
+
-            parent_scope: ParentScope {
+        // Integrate the new AST fragment into all the definition and module structures.
-                module: invocation.module,
+        fragment.visit_with(&mut DefCollector::new(&mut self.definitions, expansion));
-                expansion: expn_id,
+        let output_legacy_scope = self.build_reduced_graph(fragment, parent_scope);
-                legacy: invocation.parent_legacy_scope,
+        self.output_legacy_scopes.insert(expansion, output_legacy_scope);
-                derives: Vec::new(),
-            },
-        };
-        fragment.visit_with(&mut visitor);
-        invocation.output_legacy_scope.set(Some(visitor.parent_scope.legacy));
     }
 
     fn register_builtin_macro(&mut self, ident: ast::Ident, ext: SyntaxExtension) {
@@ -182,13 +149,14 @@ impl<'a> base::Resolver for Resolver<'a> {
 
     fn resolve_macro_invocation(&mut self, invoc: &Invocation, invoc_id: ExpnId, force: bool)
                                 -> Result<Option<Lrc<SyntaxExtension>>, Indeterminate> {
-        let (path, kind, derives_in_scope, after_derive) = match invoc.kind {
+        let parent_scope = self.invocation_parent_scopes[&invoc_id];
+        let (path, kind, derives, after_derive) = match invoc.kind {
             InvocationKind::Attr { ref attr, ref derives, after_derive, .. } =>
-                (&attr.path, MacroKind::Attr, derives.clone(), after_derive),
+                (&attr.path, MacroKind::Attr, self.arenas.alloc_ast_paths(derives), after_derive),
             InvocationKind::Bang { ref mac, .. } =>
-                (&mac.path, MacroKind::Bang, Vec::new(), false),
+                (&mac.path, MacroKind::Bang, &[][..], false),
             InvocationKind::Derive { ref path, .. } =>
-                (path, MacroKind::Derive, Vec::new(), false),
+                (path, MacroKind::Derive, &[][..], false),
             InvocationKind::DeriveContainer { ref derives, .. } => {
                 // Block expansion of derives in the container until we know whether one of them
                 // is a built-in `Copy`. Skip the resolution if there's only one derive - either
@@ -196,10 +164,9 @@ impl<'a> base::Resolver for Resolver<'a> {
                 // will automatically knows about itself.
                 let mut result = Ok(None);
                 if derives.len() > 1 {
-                    let parent_scope = &self.invoc_parent_scope(invoc_id, Vec::new());
                     for path in derives {
                         match self.resolve_macro_path(path, Some(MacroKind::Derive),
-                                                      parent_scope, true, force) {
+                                                      &parent_scope, true, force) {
                             Ok((Some(ref ext), _)) if ext.is_derive_copy => {
                                 self.add_derives(invoc.expansion_data.id, SpecialDerives::COPY);
                                 return Ok(None);
@@ -213,11 +180,14 @@ impl<'a> base::Resolver for Resolver<'a> {
             }
         };
 
-        let parent_scope = &self.invoc_parent_scope(invoc_id, derives_in_scope);
+        // Derives are not included when `invocations` are collected, so we have to add them here.
+        let parent_scope = &ParentScope { derives, ..parent_scope };
         let (ext, res) = self.smart_resolve_macro_path(path, kind, parent_scope, force)?;
 
         let span = invoc.span();
-        invoc.expansion_data.id.set_expn_info(ext.expn_info(span, fast_print_path(path)));
+        invoc.expansion_data.id.set_expn_data(
+            ext.expn_data(parent_scope.expansion, span, fast_print_path(path))
+        );
 
         if let Res::Def(_, def_id) = res {
             if after_derive {
@@ -251,20 +221,6 @@ impl<'a> base::Resolver for Resolver<'a> {
 }
 
 impl<'a> Resolver<'a> {
-    pub fn dummy_parent_scope(&self) -> ParentScope<'a> {
-        self.invoc_parent_scope(ExpnId::root(), Vec::new())
-    }
-
-    fn invoc_parent_scope(&self, invoc_id: ExpnId, derives: Vec<ast::Path>) -> ParentScope<'a> {
-        let invoc = self.invocations[&invoc_id];
-        ParentScope {
-            module: invoc.module.nearest_item_scope(),
-            expansion: invoc_id.parent(),
-            legacy: invoc.parent_legacy_scope,
-            derives,
-        }
-    }
-
     /// Resolve macro path with error reporting and recovery.
     fn smart_resolve_macro_path(
         &mut self,
@@ -346,8 +302,7 @@ impl<'a> Resolver<'a> {
 
         // Possibly apply the macro helper hack
         if kind == Some(MacroKind::Bang) && path.len() == 1 &&
-           path[0].ident.span.ctxt().outer_expn_info()
+           path[0].ident.span.ctxt().outer_expn_data().local_inner_macros {
-               .map_or(false, |info| info.local_inner_macros) {
             let root = Ident::new(kw::DollarCrate, path[0].ident.span);
             path.insert(0, Segment::from_ident(root));
         }
@@ -367,8 +322,8 @@ impl<'a> Resolver<'a> {
 
             if trace {
                 let kind = kind.expect("macro kind must be specified if tracing is enabled");
-                parent_scope.module.multi_segment_macro_resolutions.borrow_mut()
+                self.multi_segment_macro_resolutions
-                    .push((path, path_span, kind, parent_scope.clone(), res.ok()));
+                    .push((path, path_span, kind, *parent_scope, res.ok()));
             }
 
             self.prohibit_imported_non_macro_attrs(None, res.ok(), path_span);
@@ -384,8 +339,8 @@ impl<'a> Resolver<'a> {
 
             if trace {
                 let kind = kind.expect("macro kind must be specified if tracing is enabled");
-                parent_scope.module.single_segment_macro_resolutions.borrow_mut()
+                self.single_segment_macro_resolutions
-                    .push((path[0].ident, kind, parent_scope.clone(), binding.ok()));
+                    .push((path[0].ident, kind, *parent_scope, binding.ok()));
             }
 
             let res = binding.map(|binding| binding.res());
@@ -454,8 +409,8 @@ impl<'a> Resolver<'a> {
             let result = match scope {
                 Scope::DeriveHelpers => {
                     let mut result = Err(Determinacy::Determined);
-                    for derive in &parent_scope.derives {
+                    for derive in parent_scope.derives {
-                        let parent_scope = &ParentScope { derives: Vec::new(), ..*parent_scope };
+                        let parent_scope = &ParentScope { derives: &[], ..*parent_scope };
                         match this.resolve_macro_path(derive, Some(MacroKind::Derive),
                                                       parent_scope, true, force) {
                             Ok((Some(ext), _)) => if ext.helper_attrs.contains(&ident.name) {
@@ -475,8 +430,9 @@ impl<'a> Resolver<'a> {
                 Scope::MacroRules(legacy_scope) => match legacy_scope {
                     LegacyScope::Binding(legacy_binding) if ident == legacy_binding.ident =>
                         Ok((legacy_binding.binding, Flags::MACRO_RULES)),
-                    LegacyScope::Invocation(invoc) if invoc.output_legacy_scope.get().is_none() =>
+                    LegacyScope::Invocation(invoc_id)
-                        Err(Determinacy::Undetermined),
+                        if !this.output_legacy_scopes.contains_key(&invoc_id) =>
+                            Err(Determinacy::Undetermined),
                     _ => Err(Determinacy::Determined),
                 }
                 Scope::CrateRoot => {
@@ -500,7 +456,7 @@ impl<'a> Resolver<'a> {
                     }
                 }
                 Scope::Module(module) => {
-                    let adjusted_parent_scope = &ParentScope { module, ..parent_scope.clone() };
+                    let adjusted_parent_scope = &ParentScope { module, ..*parent_scope };
                     let binding = this.resolve_ident_in_module_unadjusted_ext(
                         ModuleOrUniformRoot::Module(module),
                         ident,
@@ -575,7 +531,7 @@ impl<'a> Resolver<'a> {
                             false,
                             path_span,
                         ) {
-                            if use_prelude || this.is_builtin_macro(binding.res().opt_def_id()) {
+                            if use_prelude || this.is_builtin_macro(binding.res()) {
                                 result = Ok((binding, Flags::PRELUDE | Flags::MISC_FROM_PRELUDE));
                             }
                         }
@@ -694,7 +650,7 @@ impl<'a> Resolver<'a> {
         }
     }
 
-    pub fn finalize_current_module_macro_resolutions(&mut self, module: Module<'a>) {
+    crate fn finalize_macro_resolutions(&mut self) {
         let check_consistency = |this: &mut Self, path: &[Segment], span, kind: MacroKind,
                                  initial_res: Option<Res>, res: Res| {
             if let Some(initial_res) = initial_res {
@@ -730,8 +686,7 @@ impl<'a> Resolver<'a> {
             }
         };
 
-        let macro_resolutions =
+        let macro_resolutions = mem::take(&mut self.multi_segment_macro_resolutions);
-            mem::take(&mut *module.multi_segment_macro_resolutions.borrow_mut());
         for (mut path, path_span, kind, parent_scope, initial_res) in macro_resolutions {
             // FIXME: Path resolution will ICE if segment IDs present.
             for seg in &mut path { seg.id = None; }
@@ -758,8 +713,7 @@ impl<'a> Resolver<'a> {
             }
         }
 
-        let macro_resolutions =
+        let macro_resolutions = mem::take(&mut self.single_segment_macro_resolutions);
-            mem::take(&mut *module.single_segment_macro_resolutions.borrow_mut());
         for (ident, kind, parent_scope, initial_binding) in macro_resolutions {
             match self.early_resolve_ident_in_lexical_scope(ident, ScopeSet::Macro(kind),
                                                             &parent_scope, true, true, ident.span) {
@@ -784,7 +738,7 @@ impl<'a> Resolver<'a> {
             }
         }
 
-        let builtin_attrs = mem::take(&mut *module.builtin_attrs.borrow_mut());
+        let builtin_attrs = mem::take(&mut self.builtin_attrs);
         for (ident, parent_scope) in builtin_attrs {
             let _ = self.early_resolve_ident_in_lexical_scope(
                 ident, ScopeSet::Macro(MacroKind::Attr), &parent_scope, true, true, ident.span

src/librustc_resolve/resolve_imports.rs

@@ -1,3 +1,5 @@
+//! A bunch of methods and structures more or less related to resolving imports.
+
 use ImportDirectiveSubclass::*;
 
 use crate::{AmbiguityError, AmbiguityKind, AmbiguityErrorMisc};
@@ -394,7 +396,7 @@ impl<'a> Resolver<'a> {
             match ident.span.glob_adjust(module.expansion, glob_import.span) {
                 Some(Some(def)) => {
                     tmp_parent_scope =
-                        ParentScope { module: self.macro_def_scope(def), ..parent_scope.clone() };
+                        ParentScope { module: self.macro_def_scope(def), ..*parent_scope };
                     adjusted_parent_scope = &tmp_parent_scope;
                 }
                 Some(None) => {}
@@ -848,7 +850,7 @@ impl<'a, 'b> ImportResolver<'a, 'b> {
         directive.vis.set(orig_vis);
         let module = match path_res {
             PathResult::Module(module) => {
-                // Consistency checks, analogous to `finalize_current_module_macro_resolutions`.
+                // Consistency checks, analogous to `finalize_macro_resolutions`.
                 if let Some(initial_module) = directive.imported_module.get() {
                     if !ModuleOrUniformRoot::same_def(module, initial_module) && no_ambiguity {
                         span_bug!(directive.span, "inconsistent resolution for an import");
@@ -973,7 +975,7 @@ impl<'a, 'b> ImportResolver<'a, 'b> {
 
             match binding {
                 Ok(binding) => {
-                    // Consistency checks, analogous to `finalize_current_module_macro_resolutions`.
+                    // Consistency checks, analogous to `finalize_macro_resolutions`.
                     let initial_res = source_bindings[ns].get().map(|initial_binding| {
                         all_ns_err = false;
                         if let Some(target_binding) = target_bindings[ns].get() {

src/librustc_save_analysis/lib.rs

@@ -1156,7 +1156,7 @@ fn escape(s: String) -> String {
 // Helper function to determine if a span came from a
 // macro expansion or syntax extension.
 fn generated_code(span: Span) -> bool {
-    span.ctxt() != NO_EXPANSION || span.is_dummy()
+    span.from_expansion() || span.is_dummy()
 }
 
 // DefId::index is a newtype and so the JSON serialisation is ugly. Therefore

src/librustc_typeck/check/demand.rs

@@ -347,9 +347,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             sp,
         );
 
-        // Check the `expn_info()` to see if this is a macro; if so, it's hard to
+        // If the span is from a macro, then it's hard to extract the text
-        // extract the text and make a good suggestion, so don't bother.
+        // and make a good suggestion, so don't bother.
-        let is_macro = sp.ctxt().outer_expn_info().is_some();
+        let is_macro = sp.from_expansion();
 
         match (&expr.node, &expected.sty, &checked_ty.sty) {
             (_, &ty::Ref(_, exp, _), &ty::Ref(_, check, _)) => match (&exp.sty, &check.sty) {
@@ -554,6 +554,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             // FIXME(estebank): modify once we decide to suggest `as` casts
             return false;
         }
+        if !self.tcx.sess.source_map().span_to_filename(expr.span).is_real() {
+            // Ignore if span is from within a macro.
+            return false;
+        }
 
         // If casting this expression to a given numeric type would be appropriate in case of a type
         // mismatch.

src/librustc_typeck/check/expr.rs

@@ -24,6 +24,7 @@ use syntax::source_map::Span;
 use syntax::util::lev_distance::find_best_match_for_name;
 use rustc::hir;
 use rustc::hir::{ExprKind, QPath};
+use rustc::hir::def_id::DefId;
 use rustc::hir::def::{CtorKind, Res, DefKind};
 use rustc::hir::ptr::P;
 use rustc::infer;
@@ -1336,114 +1337,180 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         autoderef.unambiguous_final_ty(self);
 
         if let Some((did, field_ty)) = private_candidate {
-            let struct_path = self.tcx().def_path_str(did);
+            self.ban_private_field_access(expr, expr_t, field, did);
-            let mut err = struct_span_err!(self.tcx().sess, expr.span, E0616,
+            return field_ty;
-                                           "field `{}` of struct `{}` is private",
-                                           field, struct_path);
-            // Also check if an accessible method exists, which is often what is meant.
-            if self.method_exists(field, expr_t, expr.hir_id, false)
-                && !self.expr_in_place(expr.hir_id)
-            {
-                self.suggest_method_call(
-                    &mut err,
-                    &format!("a method `{}` also exists, call it with parentheses", field),
-                    field,
-                    expr_t,
-                    expr.hir_id,
-                );
-            }
-            err.emit();
-            field_ty
-        } else if field.name == kw::Invalid {
-            self.tcx().types.err
-        } else if self.method_exists(field, expr_t, expr.hir_id, true) {
-            let mut err = type_error_struct!(self.tcx().sess, field.span, expr_t, E0615,
-                               "attempted to take value of method `{}` on type `{}`",
-                               field, expr_t);
-
-            if !self.expr_in_place(expr.hir_id) {
-                self.suggest_method_call(
-                    &mut err,
-                    "use parentheses to call the method",
-                    field,
-                    expr_t,
-                    expr.hir_id
-                );
-            } else {
-                err.help("methods are immutable and cannot be assigned to");
-            }
-
-            err.emit();
-            self.tcx().types.err
-        } else {
-            if !expr_t.is_primitive_ty() {
-                let mut err = self.no_such_field_err(field.span, field, expr_t);
-
-                match expr_t.sty {
-                    ty::Adt(def, _) if !def.is_enum() => {
-                        if let Some(suggested_field_name) =
-                            Self::suggest_field_name(def.non_enum_variant(),
-                                                     &field.as_str(), vec![]) {
-                                err.span_suggestion(
-                                    field.span,
-                                    "a field with a similar name exists",
-                                    suggested_field_name.to_string(),
-                                    Applicability::MaybeIncorrect,
-                                );
-                            } else {
-                                err.span_label(field.span, "unknown field");
-                                let struct_variant_def = def.non_enum_variant();
-                                let field_names = self.available_field_names(struct_variant_def);
-                                if !field_names.is_empty() {
-                                    err.note(&format!("available fields are: {}",
-                                                      self.name_series_display(field_names)));
-                                }
-                            };
-                    }
-                    ty::Array(_, len) => {
-                        if let (Some(len), Ok(user_index)) = (
-                            len.try_eval_usize(self.tcx, self.param_env),
-                            field.as_str().parse::<u64>()
-                        ) {
-                            let base = self.tcx.sess.source_map()
-                                .span_to_snippet(base.span)
-                                .unwrap_or_else(|_|
-                                    self.tcx.hir().hir_to_pretty_string(base.hir_id));
-                            let help = "instead of using tuple indexing, use array indexing";
-                            let suggestion = format!("{}[{}]", base, field);
-                            let applicability = if len < user_index {
-                                Applicability::MachineApplicable
-                            } else {
-                                Applicability::MaybeIncorrect
-                            };
-                            err.span_suggestion(
-                                expr.span, help, suggestion, applicability
-                            );
-                        }
-                    }
-                    ty::RawPtr(..) => {
-                        let base = self.tcx.sess.source_map()
-                            .span_to_snippet(base.span)
-                            .unwrap_or_else(|_| self.tcx.hir().hir_to_pretty_string(base.hir_id));
-                        let msg = format!("`{}` is a raw pointer; try dereferencing it", base);
-                        let suggestion = format!("(*{}).{}", base, field);
-                        err.span_suggestion(
-                            expr.span,
-                            &msg,
-                            suggestion,
-                            Applicability::MaybeIncorrect,
-                        );
-                    }
-                    _ => {}
-                }
-                err
-            } else {
-                type_error_struct!(self.tcx().sess, field.span, expr_t, E0610,
-                                   "`{}` is a primitive type and therefore doesn't have fields",
-                                   expr_t)
-            }.emit();
-            self.tcx().types.err
         }
+
+        if field.name == kw::Invalid {
+        } else if self.method_exists(field, expr_t, expr.hir_id, true) {
+            self.ban_take_value_of_method(expr, expr_t, field);
+        } else if !expr_t.is_primitive_ty() {
+            let mut err = self.no_such_field_err(field.span, field, expr_t);
+
+            match expr_t.sty {
+                ty::Adt(def, _) if !def.is_enum() => {
+                    self.suggest_fields_on_recordish(&mut err, def, field);
+                }
+                ty::Array(_, len) => {
+                    self.maybe_suggest_array_indexing(&mut err, expr, base, field, len);
+                }
+                ty::RawPtr(..) => {
+                    self.suggest_first_deref_field(&mut err, expr, base, field);
+                }
+                _ => {}
+            }
+
+            if field.name == kw::Await {
+                // We know by construction that `<expr>.await` is either on Rust 2015
+                // or results in `ExprKind::Await`. Suggest switching the edition to 2018.
+                err.note("to `.await` a `Future`, switch to Rust 2018");
+                err.help("set `edition = \"2018\"` in `Cargo.toml`");
+                err.note("for more on editions, read https://doc.rust-lang.org/edition-guide");
+            }
+
+            err.emit();
+        } else {
+            type_error_struct!(
+                self.tcx().sess,
+                field.span,
+                expr_t,
+                E0610,
+                "`{}` is a primitive type and therefore doesn't have fields",
+                expr_t
+            )
+            .emit();
+        }
+
+        self.tcx().types.err
+    }
+
+    fn ban_private_field_access(
+        &self,
+        expr: &hir::Expr,
+        expr_t: Ty<'tcx>,
+        field: ast::Ident,
+        base_did: DefId,
+    ) {
+        let struct_path = self.tcx().def_path_str(base_did);
+        let mut err = struct_span_err!(
+            self.tcx().sess,
+            expr.span,
+            E0616,
+            "field `{}` of struct `{}` is private",
+            field,
+            struct_path
+        );
+        // Also check if an accessible method exists, which is often what is meant.
+        if self.method_exists(field, expr_t, expr.hir_id, false)
+            && !self.expr_in_place(expr.hir_id)
+        {
+            self.suggest_method_call(
+                &mut err,
+                &format!("a method `{}` also exists, call it with parentheses", field),
+                field,
+                expr_t,
+                expr.hir_id,
+            );
+        }
+        err.emit();
+    }
+
+    fn ban_take_value_of_method(&self, expr: &hir::Expr, expr_t: Ty<'tcx>, field: ast::Ident) {
+        let mut err = type_error_struct!(
+            self.tcx().sess,
+            field.span,
+            expr_t,
+            E0615,
+            "attempted to take value of method `{}` on type `{}`",
+            field,
+            expr_t
+        );
+
+        if !self.expr_in_place(expr.hir_id) {
+            self.suggest_method_call(
+                &mut err,
+                "use parentheses to call the method",
+                field,
+                expr_t,
+                expr.hir_id
+            );
+        } else {
+            err.help("methods are immutable and cannot be assigned to");
+        }
+
+        err.emit();
+    }
+
+    fn suggest_fields_on_recordish(
+        &self,
+        err: &mut DiagnosticBuilder<'_>,
+        def: &'tcx ty::AdtDef,
+        field: ast::Ident,
+    ) {
+        if let Some(suggested_field_name) =
+            Self::suggest_field_name(def.non_enum_variant(), &field.as_str(), vec![])
+        {
+            err.span_suggestion(
+                field.span,
+                "a field with a similar name exists",
+                suggested_field_name.to_string(),
+                Applicability::MaybeIncorrect,
+            );
+        } else {
+            err.span_label(field.span, "unknown field");
+            let struct_variant_def = def.non_enum_variant();
+            let field_names = self.available_field_names(struct_variant_def);
+            if !field_names.is_empty() {
+                err.note(&format!("available fields are: {}",
+                                    self.name_series_display(field_names)));
+            }
+        }
+    }
+
+    fn maybe_suggest_array_indexing(
+        &self,
+        err: &mut DiagnosticBuilder<'_>,
+        expr: &hir::Expr,
+        base: &hir::Expr,
+        field: ast::Ident,
+        len: &ty::Const<'tcx>,
+    ) {
+        if let (Some(len), Ok(user_index)) = (
+            len.try_eval_usize(self.tcx, self.param_env),
+            field.as_str().parse::<u64>()
+        ) {
+            let base = self.tcx.sess.source_map()
+                .span_to_snippet(base.span)
+                .unwrap_or_else(|_| self.tcx.hir().hir_to_pretty_string(base.hir_id));
+            let help = "instead of using tuple indexing, use array indexing";
+            let suggestion = format!("{}[{}]", base, field);
+            let applicability = if len < user_index {
+                Applicability::MachineApplicable
+            } else {
+                Applicability::MaybeIncorrect
+            };
+            err.span_suggestion(expr.span, help, suggestion, applicability);
+        }
+    }
+
+    fn suggest_first_deref_field(
+        &self,
+        err: &mut DiagnosticBuilder<'_>,
+        expr: &hir::Expr,
+        base: &hir::Expr,
+        field: ast::Ident,
+    ) {
+        let base = self.tcx.sess.source_map()
+            .span_to_snippet(base.span)
+            .unwrap_or_else(|_| self.tcx.hir().hir_to_pretty_string(base.hir_id));
+        let msg = format!("`{}` is a raw pointer; try dereferencing it", base);
+        let suggestion = format!("(*{}).{}", base, field);
+        err.span_suggestion(
+            expr.span,
+            &msg,
+            suggestion,
+            Applicability::MaybeIncorrect,
+        );
     }
 
     fn no_such_field_err<T: Display>(&self, span: Span, field: T, expr_t: &ty::TyS<'_>)

src/librustc_typeck/check/method/suggest.rs

@@ -985,7 +985,7 @@ impl hir::intravisit::Visitor<'tcx> for UsePlacementFinder<'tcx> {
                 hir::ItemKind::Use(..) => {
                     // Don't suggest placing a `use` before the prelude
                     // import or other generated ones.
-                    if item.span.ctxt().outer_expn_info().is_none() {
+                    if !item.span.from_expansion() {
                         self.span = Some(item.span.shrink_to_lo());
                         self.found_use = true;
                         return;
@@ -995,7 +995,7 @@ impl hir::intravisit::Visitor<'tcx> for UsePlacementFinder<'tcx> {
                 hir::ItemKind::ExternCrate(_) => {}
                 // ...but do place them before the first other item.
                 _ => if self.span.map_or(true, |span| item.span < span ) {
-                    if item.span.ctxt().outer_expn_info().is_none() {
+                    if !item.span.from_expansion() {
                         // Don't insert between attributes and an item.
                         if item.attrs.is_empty() {
                             self.span = Some(item.span.shrink_to_lo());

src/librustc_typeck/check/mod.rs

@@ -2943,7 +2943,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             (PlaceOp::Index, false) => (self.tcx.lang_items().index_trait(), sym::index),
             (PlaceOp::Index, true) => (self.tcx.lang_items().index_mut_trait(), sym::index_mut),
         };
-        (tr, ast::Ident::with_empty_ctxt(name))
+        (tr, ast::Ident::with_dummy_span(name))
     }
 
     fn try_overloaded_place_op(&self,

src/librustdoc/clean/mod.rs

@@ -930,7 +930,7 @@ impl Attributes {
             if attr.check_name(sym::enable) {
                 if let Some(feat) = attr.value_str() {
                     let meta = attr::mk_name_value_item_str(
-                        Ident::with_empty_ctxt(sym::target_feature), feat, DUMMY_SP
+                        Ident::with_dummy_span(sym::target_feature), feat, DUMMY_SP
                     );
                     if let Ok(feat_cfg) = Cfg::parse(&meta) {
                         cfg &= feat_cfg;

src/librustdoc/passes/collect_intra_doc_links.rs

@@ -4,6 +4,7 @@ use rustc::hir::def_id::DefId;
 use rustc::hir;
 use rustc::lint as lint;
 use rustc::ty;
+use rustc_resolve::ParentScope;
 use syntax;
 use syntax::ast::{self, Ident};
 use syntax::ext::base::SyntaxExtensionKind;
@@ -431,7 +432,7 @@ fn macro_resolve(cx: &DocContext<'_>, path_str: &str) -> Option<Res> {
     let path = ast::Path::from_ident(Ident::from_str(path_str));
     cx.enter_resolver(|resolver| {
         if let Ok((Some(ext), res)) = resolver.resolve_macro_path(
-            &path, None, &resolver.dummy_parent_scope(), false, false
+            &path, None, &ParentScope::module(resolver.graph_root), false, false
         ) {
             if let SyntaxExtensionKind::LegacyBang { .. } = ext.kind {
                 return Some(res.map_id(|_| panic!("unexpected id")));

src/libsyntax/attr/mod.rs

@@ -327,7 +327,7 @@ impl Attribute {
         if self.is_sugared_doc {
             let comment = self.value_str().unwrap();
             let meta = mk_name_value_item_str(
-                Ident::with_empty_ctxt(sym::doc),
+                Ident::with_dummy_span(sym::doc),
                 Symbol::intern(&strip_doc_comment_decoration(&comment.as_str())),
                 DUMMY_SP,
             );
@@ -412,7 +412,7 @@ pub fn mk_sugared_doc_attr(text: Symbol, span: Span) -> Attribute {
     Attribute {
         id: mk_attr_id(),
         style,
-        path: Path::from_ident(Ident::with_empty_ctxt(sym::doc).with_span_pos(span)),
+        path: Path::from_ident(Ident::with_dummy_span(sym::doc).with_span_pos(span)),
         tokens: MetaItemKind::NameValue(lit).tokens(span),
         is_sugared_doc: true,
         span,

src/libsyntax/diagnostics/plugin.rs

@@ -172,7 +172,7 @@ pub fn expand_build_diagnostic_array<'cx>(ecx: &'cx mut ExtCtxt<'_>,
             (descriptions.len(), ecx.expr_vec(span, descriptions))
         });
 
-    let static_ = ecx.lifetime(span, Ident::with_empty_ctxt(kw::StaticLifetime));
+    let static_ = ecx.lifetime(span, Ident::with_dummy_span(kw::StaticLifetime));
     let ty_str = ecx.ty_rptr(
         span,
         ecx.ty_ident(span, ecx.ident_of("str")),

src/libsyntax/ext/base.rs

@@ -15,7 +15,7 @@ use crate::tokenstream::{self, TokenStream, TokenTree};
 use errors::{DiagnosticBuilder, DiagnosticId};
 use smallvec::{smallvec, SmallVec};
 use syntax_pos::{FileName, Span, MultiSpan, DUMMY_SP};
-use syntax_pos::hygiene::{ExpnInfo, ExpnKind};
+use syntax_pos::hygiene::{ExpnData, ExpnKind};
 
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::sync::{self, Lrc};
@@ -640,10 +640,11 @@ impl SyntaxExtension {
         SyntaxExtension::default(SyntaxExtensionKind::NonMacroAttr { mark_used }, edition)
     }
 
-    pub fn expn_info(&self, call_site: Span, descr: Symbol) -> ExpnInfo {
+    pub fn expn_data(&self, parent: ExpnId, call_site: Span, descr: Symbol) -> ExpnData {
-        ExpnInfo {
+        ExpnData {
-            call_site,
             kind: ExpnKind::Macro(self.macro_kind(), descr),
+            parent,
+            call_site,
             def_site: self.span,
             default_transparency: self.default_transparency,
             allow_internal_unstable: self.allow_internal_unstable.clone(),
@@ -707,7 +708,7 @@ pub struct ExpansionData {
 
 /// One of these is made during expansion and incrementally updated as we go;
 /// when a macro expansion occurs, the resulting nodes have the `backtrace()
-/// -> expn_info` of their expansion context stored into their span.
+/// -> expn_data` of their expansion context stored into their span.
 pub struct ExtCtxt<'a> {
     pub parse_sess: &'a parse::ParseSess,
     pub ecfg: expand::ExpansionConfig<'a>,
@@ -756,13 +757,10 @@ impl<'a> ExtCtxt<'a> {
     pub fn parse_sess(&self) -> &'a parse::ParseSess { self.parse_sess }
     pub fn cfg(&self) -> &ast::CrateConfig { &self.parse_sess.config }
     pub fn call_site(&self) -> Span {
-        match self.current_expansion.id.expn_info() {
+        self.current_expansion.id.expn_data().call_site
-            Some(expn_info) => expn_info.call_site,
-            None => DUMMY_SP,
-        }
     }
     pub fn backtrace(&self) -> SyntaxContext {
-        SyntaxContext::empty().apply_mark(self.current_expansion.id)
+        SyntaxContext::root().apply_mark(self.current_expansion.id)
     }
 
     /// Returns span for the macro which originally caused the current expansion to happen.
@@ -772,17 +770,13 @@ impl<'a> ExtCtxt<'a> {
         let mut ctxt = self.backtrace();
         let mut last_macro = None;
         loop {
-            if ctxt.outer_expn_info().map_or(None, |info| {
+            let expn_data = ctxt.outer_expn_data();
-                if info.kind.descr() == sym::include {
+            // Stop going up the backtrace once include! is encountered
-                    // Stop going up the backtrace once include! is encountered
+            if expn_data.is_root() || expn_data.kind.descr() == sym::include {
-                    return None;
+                break;
-                }
-                ctxt = info.call_site.ctxt();
-                last_macro = Some(info.call_site);
-                Some(())
-            }).is_none() {
-                break
             }
+            ctxt = expn_data.call_site.ctxt();
+            last_macro = Some(expn_data.call_site);
         }
         last_macro
     }
@@ -872,7 +866,7 @@ impl<'a> ExtCtxt<'a> {
     pub fn std_path(&self, components: &[Symbol]) -> Vec<ast::Ident> {
         let def_site = DUMMY_SP.apply_mark(self.current_expansion.id);
         iter::once(Ident::new(kw::DollarCrate, def_site))
-            .chain(components.iter().map(|&s| Ident::with_empty_ctxt(s)))
+            .chain(components.iter().map(|&s| Ident::with_dummy_span(s)))
             .collect()
     }
     pub fn name_of(&self, st: &str) -> ast::Name {

src/libsyntax/ext/build.rs

@@ -340,7 +340,7 @@ impl<'a> ExtCtxt<'a> {
         self.expr_path(self.path_ident(span, id))
     }
     pub fn expr_self(&self, span: Span) -> P<ast::Expr> {
-        self.expr_ident(span, Ident::with_empty_ctxt(kw::SelfLower))
+        self.expr_ident(span, Ident::with_dummy_span(kw::SelfLower))
     }
 
     pub fn expr_binary(&self, sp: Span, op: ast::BinOpKind,

src/libsyntax/ext/expand.rs

@@ -5,7 +5,7 @@ use crate::source_map::respan;
 use crate::config::StripUnconfigured;
 use crate::ext::base::*;
 use crate::ext::proc_macro::collect_derives;
-use crate::ext::hygiene::{ExpnId, SyntaxContext, ExpnInfo, ExpnKind};
+use crate::ext::hygiene::{ExpnId, SyntaxContext, ExpnData, ExpnKind};
 use crate::ext::tt::macro_rules::annotate_err_with_kind;
 use crate::ext::placeholders::{placeholder, PlaceholderExpander};
 use crate::feature_gate::{self, Features, GateIssue, is_builtin_attr, emit_feature_err};
@@ -353,7 +353,7 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
                 derives.reserve(traits.len());
                 invocations.reserve(traits.len());
                 for path in traits {
-                    let expn_id = ExpnId::fresh(self.cx.current_expansion.id, None);
+                    let expn_id = ExpnId::fresh(None);
                     derives.push(expn_id);
                     invocations.push(Invocation {
                         kind: InvocationKind::Derive { path, item: item.clone() },
@@ -475,11 +475,11 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
         }
 
         if self.cx.current_expansion.depth > self.cx.ecfg.recursion_limit {
-            let info = self.cx.current_expansion.id.expn_info().unwrap();
+            let expn_data = self.cx.current_expansion.id.expn_data();
             let suggested_limit = self.cx.ecfg.recursion_limit * 2;
-            let mut err = self.cx.struct_span_err(info.call_site,
+            let mut err = self.cx.struct_span_err(expn_data.call_site,
                 &format!("recursion limit reached while expanding the macro `{}`",
-                         info.kind.descr()));
+                         expn_data.kind.descr()));
             err.help(&format!(
                 "consider adding a `#![recursion_limit=\"{}\"]` attribute to your crate",
                 suggested_limit));
@@ -759,7 +759,7 @@ impl<'a> Parser<'a> {
             let msg = format!("macro expansion ignores token `{}` and any following",
                               self.this_token_to_string());
             // Avoid emitting backtrace info twice.
-            let def_site_span = self.token.span.with_ctxt(SyntaxContext::empty());
+            let def_site_span = self.token.span.with_ctxt(SyntaxContext::root());
             let mut err = self.diagnostic().struct_span_err(def_site_span, &msg);
             err.span_label(span, "caused by the macro expansion here");
             let msg = format!(
@@ -796,17 +796,20 @@ struct InvocationCollector<'a, 'b> {
 
 impl<'a, 'b> InvocationCollector<'a, 'b> {
     fn collect(&mut self, fragment_kind: AstFragmentKind, kind: InvocationKind) -> AstFragment {
-        // Expansion info for all the collected invocations is set upon their resolution,
+        // Expansion data for all the collected invocations is set upon their resolution,
         // with exception of the derive container case which is not resolved and can get
-        // its expansion info immediately.
+        // its expansion data immediately.
-        let expn_info = match &kind {
+        let expn_data = match &kind {
-            InvocationKind::DeriveContainer { item, .. } => Some(ExpnInfo::default(
+            InvocationKind::DeriveContainer { item, .. } => Some(ExpnData {
-                ExpnKind::Macro(MacroKind::Attr, sym::derive),
+                parent: self.cx.current_expansion.id,
-                item.span(), self.cx.parse_sess.edition,
+                ..ExpnData::default(
-            )),
+                    ExpnKind::Macro(MacroKind::Attr, sym::derive),
+                    item.span(), self.cx.parse_sess.edition,
+                )
+            }),
             _ => None,
         };
-        let expn_id = ExpnId::fresh(self.cx.current_expansion.id, expn_info);
+        let expn_id = ExpnId::fresh(expn_data);
         self.invocations.push(Invocation {
             kind,
             fragment_kind,
@@ -1249,21 +1252,21 @@ impl<'a, 'b> MutVisitor for InvocationCollector<'a, 'b> {
                             let include_info = vec![
                                 ast::NestedMetaItem::MetaItem(
                                     attr::mk_name_value_item_str(
-                                        Ident::with_empty_ctxt(sym::file),
+                                        Ident::with_dummy_span(sym::file),
                                         file,
                                         DUMMY_SP,
                                     ),
                                 ),
                                 ast::NestedMetaItem::MetaItem(
                                     attr::mk_name_value_item_str(
-                                        Ident::with_empty_ctxt(sym::contents),
+                                        Ident::with_dummy_span(sym::contents),
                                         src_interned,
                                         DUMMY_SP,
                                     ),
                                 ),
                             ];
 
-                            let include_ident = Ident::with_empty_ctxt(sym::include);
+                            let include_ident = Ident::with_dummy_span(sym::include);
                             let item = attr::mk_list_item(include_ident, include_info);
                             items.push(ast::NestedMetaItem::MetaItem(item));
                         }
@@ -1325,7 +1328,7 @@ impl<'a, 'b> MutVisitor for InvocationCollector<'a, 'b> {
                 }
             }
 
-            let meta = attr::mk_list_item(Ident::with_empty_ctxt(sym::doc), items);
+            let meta = attr::mk_list_item(Ident::with_dummy_span(sym::doc), items);
             *at = attr::Attribute {
                 span: at.span,
                 id: at.id,

src/libsyntax/ext/proc_macro_server.rs

@@ -362,10 +362,10 @@ pub(crate) struct Rustc<'a> {
 impl<'a> Rustc<'a> {
     pub fn new(cx: &'a ExtCtxt<'_>) -> Self {
         // No way to determine def location for a proc macro right now, so use call location.
-        let location = cx.current_expansion.id.expn_info().unwrap().call_site;
+        let location = cx.current_expansion.id.expn_data().call_site;
         let to_span = |transparency| {
             location.with_ctxt(
-                SyntaxContext::empty()
+                SyntaxContext::root()
                     .apply_mark_with_transparency(cx.current_expansion.id, transparency),
             )
         };
@@ -677,7 +677,7 @@ impl server::Span for Rustc<'_> {
         self.sess.source_map().lookup_char_pos(span.lo()).file
     }
     fn parent(&mut self, span: Self::Span) -> Option<Self::Span> {
-        span.ctxt().outer_expn_info().map(|i| i.call_site)
+        span.parent()
     }
     fn source(&mut self, span: Self::Span) -> Self::Span {
         span.source_callsite()

src/libsyntax/parse/lexer/mod.rs

@@ -4,7 +4,7 @@ use crate::symbol::{sym, Symbol};
 use crate::parse::unescape_error_reporting::{emit_unescape_error, push_escaped_char};
 
 use errors::{FatalError, DiagnosticBuilder};
-use syntax_pos::{BytePos, Pos, Span, NO_EXPANSION};
+use syntax_pos::{BytePos, Pos, Span};
 use rustc_lexer::Base;
 use rustc_lexer::unescape;
 
@@ -84,7 +84,7 @@ impl<'a> StringReader<'a> {
 
 
     fn mk_sp(&self, lo: BytePos, hi: BytePos) -> Span {
-        self.override_span.unwrap_or_else(|| Span::new(lo, hi, NO_EXPANSION))
+        self.override_span.unwrap_or_else(|| Span::with_root_ctxt(lo, hi))
     }
 
     /// Returns the next token, including trivia like whitespace or comments.

src/libsyntax/parse/lexer/tests.rs

@@ -1,41 +1,17 @@
 use super::*;
 
-use crate::ast::CrateConfig;
 use crate::symbol::Symbol;
 use crate::source_map::{SourceMap, FilePathMapping};
-use crate::feature_gate::UnstableFeatures;
 use crate::parse::token;
-use crate::diagnostics::plugin::ErrorMap;
 use crate::with_default_globals;
 use std::io;
 use std::path::PathBuf;
-use syntax_pos::{BytePos, Span, NO_EXPANSION, edition::Edition};
+use errors::{Handler, emitter::EmitterWriter};
-use rustc_data_structures::fx::{FxHashSet, FxHashMap};
+use syntax_pos::{BytePos, Span};
-use rustc_data_structures::sync::{Lock, Once};
 
 fn mk_sess(sm: Lrc<SourceMap>) -> ParseSess {
-    let emitter = errors::emitter::EmitterWriter::new(Box::new(io::sink()),
+    let emitter = EmitterWriter::new(Box::new(io::sink()), Some(sm.clone()), false, false, false);
-                                                        Some(sm.clone()),
+    ParseSess::with_span_handler(Handler::with_emitter(true, None, Box::new(emitter)), sm)
-                                                        false,
-                                                        false,
-                                                        false);
-    ParseSess {
-        span_diagnostic: errors::Handler::with_emitter(true, None, Box::new(emitter)),
-        unstable_features: UnstableFeatures::from_environment(),
-        config: CrateConfig::default(),
-        included_mod_stack: Lock::new(Vec::new()),
-        source_map: sm,
-        missing_fragment_specifiers: Lock::new(FxHashSet::default()),
-        raw_identifier_spans: Lock::new(Vec::new()),
-        registered_diagnostics: Lock::new(ErrorMap::new()),
-        buffered_lints: Lock::new(vec![]),
-        edition: Edition::from_session(),
-        ambiguous_block_expr_parse: Lock::new(FxHashMap::default()),
-        param_attr_spans: Lock::new(Vec::new()),
-        let_chains_spans: Lock::new(Vec::new()),
-        async_closure_spans: Lock::new(Vec::new()),
-        injected_crate_name: Once::new(),
-    }
 }
 
 // open a string reader for the given string
@@ -61,7 +37,7 @@ fn t1() {
         let tok1 = string_reader.next_token();
         let tok2 = Token::new(
             mk_ident("fn"),
-            Span::new(BytePos(21), BytePos(23), NO_EXPANSION),
+            Span::with_root_ctxt(BytePos(21), BytePos(23)),
         );
         assert_eq!(tok1.kind, tok2.kind);
         assert_eq!(tok1.span, tok2.span);
@@ -71,7 +47,7 @@ fn t1() {
         assert_eq!(string_reader.pos.clone(), BytePos(28));
         let tok4 = Token::new(
             mk_ident("main"),
-            Span::new(BytePos(24), BytePos(28), NO_EXPANSION),
+            Span::with_root_ctxt(BytePos(24), BytePos(28)),
         );
         assert_eq!(tok3.kind, tok4.kind);
         assert_eq!(tok3.span, tok4.span);

src/libsyntax/parse/lexer/unicode_chars.rs

@@ -3,7 +3,7 @@
 
 use super::StringReader;
 use errors::{Applicability, DiagnosticBuilder};
-use syntax_pos::{BytePos, Pos, Span, NO_EXPANSION, symbol::kw};
+use syntax_pos::{BytePos, Pos, Span, symbol::kw};
 use crate::parse::token;
 
 #[rustfmt::skip] // for line breaks
@@ -343,7 +343,7 @@ crate fn check_for_substitution<'a>(
         None => return None,
     };
 
-    let span = Span::new(pos, pos + Pos::from_usize(ch.len_utf8()), NO_EXPANSION);
+    let span = Span::with_root_ctxt(pos, pos + Pos::from_usize(ch.len_utf8()));
 
     let (ascii_name, token) = match ASCII_ARRAY.iter().find(|&&(c, _, _)| c == ascii_char) {
         Some((_ascii_char, ascii_name, token)) => (ascii_name, token),
@@ -362,10 +362,9 @@ crate fn check_for_substitution<'a>(
             ascii_char, ascii_name
         );
         err.span_suggestion(
-            Span::new(
+            Span::with_root_ctxt(
                 pos,
                 pos + Pos::from_usize('“'.len_utf8() + s.len() + '”'.len_utf8()),
-                NO_EXPANSION,
             ),
             &msg,
             format!("\"{}\"", s),

src/libsyntax/parse/mod.rs

@@ -16,6 +16,7 @@ use errors::{Applicability, FatalError, Level, Handler, ColorConfig, Diagnostic,
 use rustc_data_structures::sync::{Lrc, Lock, Once};
 use syntax_pos::{Span, SourceFile, FileName, MultiSpan};
 use syntax_pos::edition::Edition;
+use syntax_pos::hygiene::ExpnId;
 
 use rustc_data_structures::fx::{FxHashSet, FxHashMap};
 use std::borrow::Cow;
@@ -86,7 +87,7 @@ impl ParseSess {
             included_mod_stack: Lock::new(vec![]),
             source_map,
             buffered_lints: Lock::new(vec![]),
-            edition: Edition::from_session(),
+            edition: ExpnId::root().expn_data().edition,
             ambiguous_block_expr_parse: Lock::new(FxHashMap::default()),
             param_attr_spans: Lock::new(Vec::new()),
             let_chains_spans: Lock::new(Vec::new()),

src/libsyntax/parse/parser.rs

@@ -13,7 +13,6 @@ mod generics;
 use crate::ast::{self, AttrStyle, Attribute, Arg, BindingMode, StrStyle, SelfKind};
 use crate::ast::{FnDecl, Ident, IsAsync, MacDelimiter, Mutability, TyKind};
 use crate::ast::{Visibility, VisibilityKind, Unsafety, CrateSugar};
-use crate::ext::hygiene::SyntaxContext;
 use crate::source_map::{self, respan};
 use crate::parse::{SeqSep, literal, token};
 use crate::parse::lexer::UnmatchedBrace;
@@ -1101,7 +1100,7 @@ impl<'a> Parser<'a> {
 
     crate fn process_potential_macro_variable(&mut self) {
         self.token = match self.token.kind {
-            token::Dollar if self.token.span.ctxt() != SyntaxContext::empty() &&
+            token::Dollar if self.token.span.from_expansion() &&
                              self.look_ahead(1, |t| t.is_ident()) => {
                 self.bump();
                 let name = match self.token.kind {

src/libsyntax/parse/parser/module.rs

@@ -60,7 +60,7 @@ impl<'a> Parser<'a> {
                 // Record that we fetched the mod from an external file
                 if warn {
                     let attr = attr::mk_attr_outer(
-                        attr::mk_word_item(Ident::with_empty_ctxt(sym::warn_directory_ownership)));
+                        attr::mk_word_item(Ident::with_dummy_span(sym::warn_directory_ownership)));
                     attr::mark_known(&attr);
                     attrs.push(attr);
                 }

src/libsyntax/parse/tests.rs

@@ -12,7 +12,7 @@ use crate::symbol::{kw, sym};
 use crate::tests::{matches_codepattern, string_to_stream, with_error_checking_parse};
 use crate::tokenstream::{DelimSpan, TokenTree, TokenStream};
 use crate::with_default_globals;
-use syntax_pos::{Span, BytePos, Pos, NO_EXPANSION};
+use syntax_pos::{Span, BytePos, Pos};
 
 use std::path::PathBuf;
 
@@ -27,7 +27,7 @@ fn parse_item_from_source_str(name: FileName, source: String, sess: &ParseSess)
 
 // produce a syntax_pos::span
 fn sp(a: u32, b: u32) -> Span {
-    Span::new(BytePos(a), BytePos(b), NO_EXPANSION)
+    Span::with_root_ctxt(BytePos(a), BytePos(b))
 }
 
 /// Parse a string, return an expr

src/libsyntax/print/pprust.rs

@@ -123,13 +123,13 @@ pub fn print_crate<'a>(cm: &'a SourceMap,
         // of the feature gate, so we fake them up here.
 
         // #![feature(prelude_import)]
-        let pi_nested = attr::mk_nested_word_item(ast::Ident::with_empty_ctxt(sym::prelude_import));
+        let pi_nested = attr::mk_nested_word_item(ast::Ident::with_dummy_span(sym::prelude_import));
-        let list = attr::mk_list_item(ast::Ident::with_empty_ctxt(sym::feature), vec![pi_nested]);
+        let list = attr::mk_list_item(ast::Ident::with_dummy_span(sym::feature), vec![pi_nested]);
         let fake_attr = attr::mk_attr_inner(list);
         s.print_attribute(&fake_attr);
 
         // #![no_std]
-        let no_std_meta = attr::mk_word_item(ast::Ident::with_empty_ctxt(sym::no_std));
+        let no_std_meta = attr::mk_word_item(ast::Ident::with_dummy_span(sym::no_std));
         let fake_attr = attr::mk_attr_inner(no_std_meta);
         s.print_attribute(&fake_attr);
     }

src/libsyntax/source_map.rs

@@ -8,7 +8,7 @@
 //! information, source code snippets, etc.
 
 pub use syntax_pos::*;
-pub use syntax_pos::hygiene::{ExpnKind, ExpnInfo};
+pub use syntax_pos::hygiene::{ExpnKind, ExpnData};
 
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::stable_hasher::StableHasher;
@@ -29,14 +29,15 @@ mod tests;
 
 /// Returns the span itself if it doesn't come from a macro expansion,
 /// otherwise return the call site span up to the `enclosing_sp` by
-/// following the `expn_info` chain.
+/// following the `expn_data` chain.
 pub fn original_sp(sp: Span, enclosing_sp: Span) -> Span {
-    let call_site1 = sp.ctxt().outer_expn_info().map(|ei| ei.call_site);
+    let expn_data1 = sp.ctxt().outer_expn_data();
-    let call_site2 = enclosing_sp.ctxt().outer_expn_info().map(|ei| ei.call_site);
+    let expn_data2 = enclosing_sp.ctxt().outer_expn_data();
-    match (call_site1, call_site2) {
+    if expn_data1.is_root() ||
-        (None, _) => sp,
+       !expn_data2.is_root() && expn_data1.call_site == expn_data2.call_site {
-        (Some(call_site1), Some(call_site2)) if call_site1 == call_site2 => sp,
+        sp
-        (Some(call_site1), _) => original_sp(call_site1, enclosing_sp),
+    } else {
+        original_sp(expn_data1.call_site, enclosing_sp)
     }
 }
 

src/libsyntax/source_map/tests.rs

@@ -91,7 +91,7 @@ fn t6() {
 fn t7() {
     // Test span_to_lines for a span ending at the end of source_file
     let sm = init_source_map();
-    let span = Span::new(BytePos(12), BytePos(23), NO_EXPANSION);
+    let span = Span::with_root_ctxt(BytePos(12), BytePos(23));
     let file_lines = sm.span_to_lines(span).unwrap();
 
     assert_eq!(file_lines.file.name, PathBuf::from("blork.rs").into());
@@ -107,7 +107,7 @@ fn span_from_selection(input: &str, selection: &str) -> Span {
     assert_eq!(input.len(), selection.len());
     let left_index = selection.find('~').unwrap() as u32;
     let right_index = selection.rfind('~').map(|x|x as u32).unwrap_or(left_index);
-    Span::new(BytePos(left_index), BytePos(right_index + 1), NO_EXPANSION)
+    Span::with_root_ctxt(BytePos(left_index), BytePos(right_index + 1))
 }
 
 /// Tests span_to_snippet and span_to_lines for a span converting 3
@@ -137,7 +137,7 @@ fn span_to_snippet_and_lines_spanning_multiple_lines() {
 fn t8() {
     // Test span_to_snippet for a span ending at the end of source_file
     let sm = init_source_map();
-    let span = Span::new(BytePos(12), BytePos(23), NO_EXPANSION);
+    let span = Span::with_root_ctxt(BytePos(12), BytePos(23));
     let snippet = sm.span_to_snippet(span);
 
     assert_eq!(snippet, Ok("second line".to_string()));
@@ -147,7 +147,7 @@ fn t8() {
 fn t9() {
     // Test span_to_str for a span ending at the end of source_file
     let sm = init_source_map();
-    let span = Span::new(BytePos(12), BytePos(23), NO_EXPANSION);
+    let span = Span::with_root_ctxt(BytePos(12), BytePos(23));
     let sstr =  sm.span_to_string(span);
 
     assert_eq!(sstr, "blork.rs:2:1: 2:12");
@@ -198,10 +198,9 @@ impl SourceMapExtension for SourceMap {
             let lo = hi + offset;
             hi = lo + substring.len();
             if i == n {
-                let span = Span::new(
+                let span = Span::with_root_ctxt(
                     BytePos(lo as u32 + file.start_pos.0),
                     BytePos(hi as u32 + file.start_pos.0),
-                    NO_EXPANSION,
                 );
                 assert_eq!(&self.span_to_snippet(span).unwrap()[..],
                         substring);

src/libsyntax/tests.rs

@@ -9,7 +9,7 @@ use crate::with_default_globals;
 use errors::emitter::EmitterWriter;
 use errors::Handler;
 use rustc_data_structures::sync::Lrc;
-use syntax_pos::{BytePos, NO_EXPANSION, Span, MultiSpan};
+use syntax_pos::{BytePos, Span, MultiSpan};
 
 use std::io;
 use std::io::prelude::*;
@@ -169,7 +169,7 @@ fn make_span(file_text: &str, start: &Position, end: &Position) -> Span {
     let start = make_pos(file_text, start);
     let end = make_pos(file_text, end) + end.string.len(); // just after matching thing ends
     assert!(start <= end);
-    Span::new(BytePos(start as u32), BytePos(end as u32), NO_EXPANSION)
+    Span::with_root_ctxt(BytePos(start as u32), BytePos(end as u32))
 }
 
 fn make_pos(file_text: &str, pos: &Position) -> usize {

src/libsyntax/tokenstream/tests.rs

@@ -3,14 +3,14 @@ use super::*;
 use crate::ast::Name;
 use crate::with_default_globals;
 use crate::tests::string_to_stream;
-use syntax_pos::{Span, BytePos, NO_EXPANSION};
+use syntax_pos::{Span, BytePos};
 
 fn string_to_ts(string: &str) -> TokenStream {
     string_to_stream(string.to_owned())
 }
 
 fn sp(a: u32, b: u32) -> Span {
-    Span::new(BytePos(a), BytePos(b), NO_EXPANSION)
+    Span::with_root_ctxt(BytePos(a), BytePos(b))
 }
 
 #[test]

src/libsyntax_ext/deriving/clone.rs

@@ -35,7 +35,7 @@ pub fn expand_deriving_clone(cx: &mut ExtCtxt<'_>,
             match annitem.node {
                 ItemKind::Struct(_, Generics { ref params, .. }) |
                 ItemKind::Enum(_, Generics { ref params, .. }) => {
-                    let container_id = cx.current_expansion.id.parent();
+                    let container_id = cx.current_expansion.id.expn_data().parent;
                     if cx.resolver.has_derives(container_id, SpecialDerives::COPY) &&
                         !params.iter().any(|param| match param.kind {
                             ast::GenericParamKind::Type { .. } => true,
@@ -129,7 +129,7 @@ fn cs_clone_shallow(name: &str,
     if is_union {
         // let _: AssertParamIsCopy<Self>;
         let self_ty =
-            cx.ty_path(cx.path_ident(trait_span, ast::Ident::with_empty_ctxt(kw::SelfUpper)));
+            cx.ty_path(cx.path_ident(trait_span, ast::Ident::with_dummy_span(kw::SelfUpper)));
         assert_ty_bounds(cx, &mut stmts, self_ty, trait_span, "AssertParamIsCopy");
     } else {
         match *substr.fields {

src/libsyntax_ext/deriving/cmp/eq.rs

@@ -13,7 +13,7 @@ pub fn expand_deriving_eq(cx: &mut ExtCtxt<'_>,
                           mitem: &MetaItem,
                           item: &Annotatable,
                           push: &mut dyn FnMut(Annotatable)) {
-    cx.resolver.add_derives(cx.current_expansion.id.parent(), SpecialDerives::EQ);
+    cx.resolver.add_derives(cx.current_expansion.id.expn_data().parent, SpecialDerives::EQ);
 
     let inline = cx.meta_word(span, sym::inline);
     let hidden = cx.meta_list_item_word(span, sym::hidden);

src/libsyntax_ext/deriving/cmp/partial_eq.rs

@@ -13,7 +13,7 @@ pub fn expand_deriving_partial_eq(cx: &mut ExtCtxt<'_>,
                                   mitem: &MetaItem,
                                   item: &Annotatable,
                                   push: &mut dyn FnMut(Annotatable)) {
-    cx.resolver.add_derives(cx.current_expansion.id.parent(), SpecialDerives::PARTIAL_EQ);
+    cx.resolver.add_derives(cx.current_expansion.id.expn_data().parent, SpecialDerives::PARTIAL_EQ);
 
     // structures are equal if all fields are equal, and non equal, if
     // any fields are not equal or if the enum variants are different

src/libsyntax_ext/deriving/debug.rs

@@ -82,7 +82,7 @@ fn show_substructure(cx: &mut ExtCtxt<'_>, span: Span, substr: &Substructure<'_>
 
                 let expr = cx.expr_method_call(span,
                                                 builder_expr.clone(),
-                                                Ident::with_empty_ctxt(sym::field),
+                                                Ident::with_dummy_span(sym::field),
                                                 vec![field]);
 
                 // Use `let _ = expr;` to avoid triggering the
@@ -106,7 +106,7 @@ fn show_substructure(cx: &mut ExtCtxt<'_>, span: Span, substr: &Substructure<'_>
                 let field = cx.expr_addr_of(field.span, field);
                 let expr = cx.expr_method_call(span,
                                                 builder_expr.clone(),
-                                                Ident::with_empty_ctxt(sym::field),
+                                                Ident::with_dummy_span(sym::field),
                                                 vec![name, field]);
                 stmts.push(stmt_let_undescore(cx, span, expr));
             }

src/libsyntax_ext/deriving/generic/mod.rs

@@ -425,7 +425,7 @@ impl<'a> TraitDef<'a> {
                         return;
                     }
                 };
-                let container_id = cx.current_expansion.id.parent();
+                let container_id = cx.current_expansion.id.expn_data().parent;
                 let is_always_copy =
                     cx.resolver.has_derives(container_id, SpecialDerives::COPY) &&
                     has_no_type_params;
@@ -928,7 +928,7 @@ impl<'a> MethodDef<'a> {
 
         let args = {
             let self_args = explicit_self.map(|explicit_self| {
-                let ident = Ident::with_empty_ctxt(kw::SelfLower).with_span_pos(trait_.span);
+                let ident = Ident::with_dummy_span(kw::SelfLower).with_span_pos(trait_.span);
                 ast::Arg::from_self(ThinVec::default(), explicit_self, ident)
             });
             let nonself_args = arg_types.into_iter()

src/libsyntax_ext/env.rs

@@ -23,13 +23,13 @@ pub fn expand_option_env<'cx>(cx: &'cx mut ExtCtxt<'_>,
     let sp = sp.apply_mark(cx.current_expansion.id);
     let e = match env::var(&*var.as_str()) {
         Err(..) => {
-            let lt = cx.lifetime(sp, Ident::with_empty_ctxt(kw::StaticLifetime));
+            let lt = cx.lifetime(sp, Ident::with_dummy_span(kw::StaticLifetime));
             cx.expr_path(cx.path_all(sp,
                                      true,
                                      cx.std_path(&[sym::option, sym::Option, sym::None]),
                                      vec![GenericArg::Type(cx.ty_rptr(sp,
                                                      cx.ty_ident(sp,
-                                                                 Ident::with_empty_ctxt(sym::str)),
+                                                                 Ident::with_dummy_span(sym::str)),
                                                      Some(lt),
                                                      ast::Mutability::Immutable))],
                                      vec![]))

src/libsyntax_ext/global_allocator.rs

@@ -29,7 +29,7 @@ pub fn expand(
     };
 
     // Generate a bunch of new items using the AllocFnFactory
-    let span = item.span.with_ctxt(SyntaxContext::empty().apply_mark(ecx.current_expansion.id));
+    let span = item.span.with_ctxt(SyntaxContext::root().apply_mark(ecx.current_expansion.id));
     let f = AllocFnFactory {
         span,
         kind: AllocatorKind::Global,
@@ -44,7 +44,7 @@ pub fn expand(
     let const_ty = ecx.ty(span, TyKind::Tup(Vec::new()));
     let const_body = ecx.expr_block(ecx.block(span, stmts));
     let const_item =
-        ecx.item_const(span, Ident::with_empty_ctxt(kw::Underscore), const_ty, const_body);
+        ecx.item_const(span, Ident::with_dummy_span(kw::Underscore), const_ty, const_body);
 
     // Return the original item and the new methods.
     vec![Annotatable::Item(item), Annotatable::Item(const_item)]
@@ -120,7 +120,7 @@ impl AllocFnFactory<'_, '_> {
     ) -> P<Expr> {
         match *ty {
             AllocatorTy::Layout => {
-                let usize = self.cx.path_ident(self.span, Ident::with_empty_ctxt(sym::usize));
+                let usize = self.cx.path_ident(self.span, Ident::with_dummy_span(sym::usize));
                 let ty_usize = self.cx.ty_path(usize);
                 let size = ident();
                 let align = ident();
@@ -178,12 +178,12 @@ impl AllocFnFactory<'_, '_> {
     }
 
     fn usize(&self) -> P<Ty> {
-        let usize = self.cx.path_ident(self.span, Ident::with_empty_ctxt(sym::usize));
+        let usize = self.cx.path_ident(self.span, Ident::with_dummy_span(sym::usize));
         self.cx.ty_path(usize)
     }
 
     fn ptr_u8(&self) -> P<Ty> {
-        let u8 = self.cx.path_ident(self.span, Ident::with_empty_ctxt(sym::u8));
+        let u8 = self.cx.path_ident(self.span, Ident::with_dummy_span(sym::u8));
         let ty_u8 = self.cx.ty_path(u8);
         self.cx.ty_ptr(self.span, ty_u8, Mutability::Mutable)
     }

src/libsyntax_ext/lib.rs

@@ -42,7 +42,7 @@ pub mod test_harness;
 
 pub fn register_builtin_macros(resolver: &mut dyn syntax::ext::base::Resolver, edition: Edition) {
     let mut register = |name, kind| resolver.register_builtin_macro(
-        Ident::with_empty_ctxt(name), SyntaxExtension {
+        Ident::with_dummy_span(name), SyntaxExtension {
             is_builtin: true, ..SyntaxExtension::default(kind, edition)
         },
     );

src/libsyntax_ext/plugin_macro_defs.rs

@@ -11,7 +11,7 @@ use syntax::source_map::respan;
 use syntax::symbol::sym;
 use syntax::tokenstream::*;
 use syntax_pos::{Span, DUMMY_SP};
-use syntax_pos::hygiene::{ExpnId, ExpnInfo, ExpnKind, MacroKind};
+use syntax_pos::hygiene::{ExpnData, ExpnKind, MacroKind};
 
 use std::mem;
 
@@ -43,12 +43,12 @@ pub fn inject(
 ) {
     if !named_exts.is_empty() {
         let mut extra_items = Vec::new();
-        let span = DUMMY_SP.fresh_expansion(ExpnId::root(), ExpnInfo::allow_unstable(
+        let span = DUMMY_SP.fresh_expansion(ExpnData::allow_unstable(
             ExpnKind::Macro(MacroKind::Attr, sym::plugin), DUMMY_SP, edition,
             [sym::rustc_attrs][..].into(),
         ));
         for (name, ext) in named_exts {
-            resolver.register_builtin_macro(Ident::with_empty_ctxt(name), ext);
+            resolver.register_builtin_macro(Ident::with_dummy_span(name), ext);
             extra_items.push(plugin_macro_def(name, span));
         }
         // The `macro_rules` items must be inserted before any other items.

src/libsyntax_ext/proc_macro_harness.rs

@@ -3,10 +3,9 @@ use std::mem;
 use smallvec::smallvec;
 use syntax::ast::{self, Ident};
 use syntax::attr;
-use syntax::source_map::{ExpnInfo, ExpnKind, respan};
+use syntax::source_map::{ExpnData, ExpnKind, respan};
 use syntax::ext::base::{ExtCtxt, MacroKind};
 use syntax::ext::expand::{AstFragment, ExpansionConfig};
-use syntax::ext::hygiene::ExpnId;
 use syntax::ext::proc_macro::is_proc_macro_attr;
 use syntax::parse::ParseSess;
 use syntax::ptr::P;
@@ -328,7 +327,7 @@ fn mk_decls(
     custom_attrs: &[ProcMacroDef],
     custom_macros: &[ProcMacroDef],
 ) -> P<ast::Item> {
-    let span = DUMMY_SP.fresh_expansion(ExpnId::root(), ExpnInfo::allow_unstable(
+    let span = DUMMY_SP.fresh_expansion(ExpnData::allow_unstable(
         ExpnKind::Macro(MacroKind::Attr, sym::proc_macro), DUMMY_SP, cx.parse_sess.edition,
         [sym::rustc_attrs, sym::proc_macro_internals][..].into(),
     ));
@@ -337,7 +336,7 @@ fn mk_decls(
     let doc = cx.meta_list(span, sym::doc, vec![hidden]);
     let doc_hidden = cx.attribute(doc);
 
-    let proc_macro = Ident::with_empty_ctxt(sym::proc_macro);
+    let proc_macro = Ident::with_dummy_span(sym::proc_macro);
     let krate = cx.item(span,
                         proc_macro,
                         Vec::new(),
@@ -349,7 +348,7 @@ fn mk_decls(
     let custom_derive = Ident::from_str("custom_derive");
     let attr = Ident::from_str("attr");
     let bang = Ident::from_str("bang");
-    let crate_kw = Ident::with_empty_ctxt(kw::Crate);
+    let crate_kw = Ident::with_dummy_span(kw::Crate);
 
     let decls = {
         let local_path = |sp: Span, name| {

src/libsyntax_ext/standard_library_imports.rs

@@ -1,8 +1,8 @@
 use syntax::{ast, attr};
 use syntax::edition::Edition;
-use syntax::ext::hygiene::{ExpnId, MacroKind};
+use syntax::ext::hygiene::MacroKind;
 use syntax::ptr::P;
-use syntax::source_map::{ExpnInfo, ExpnKind, dummy_spanned, respan};
+use syntax::source_map::{ExpnData, ExpnKind, dummy_spanned, respan};
 use syntax::symbol::{Ident, Symbol, kw, sym};
 use syntax_pos::DUMMY_SP;
 
@@ -32,7 +32,7 @@ pub fn inject(
         // HACK(eddyb) gensym the injected crates on the Rust 2018 edition,
         // so they don't accidentally interfere with the new import paths.
         let orig_name_sym = Symbol::intern(orig_name_str);
-        let orig_name_ident = Ident::with_empty_ctxt(orig_name_sym);
+        let orig_name_ident = Ident::with_dummy_span(orig_name_sym);
         let (rename, orig_name) = if rust_2018 {
             (orig_name_ident.gensym(), Some(orig_name_sym))
         } else {
@@ -40,7 +40,7 @@ pub fn inject(
         };
         krate.module.items.insert(0, P(ast::Item {
             attrs: vec![attr::mk_attr_outer(
-                attr::mk_word_item(ast::Ident::with_empty_ctxt(sym::macro_use))
+                attr::mk_word_item(ast::Ident::with_dummy_span(sym::macro_use))
             )],
             vis: dummy_spanned(ast::VisibilityKind::Inherited),
             node: ast::ItemKind::ExternCrate(alt_std_name.or(orig_name)),
@@ -55,7 +55,7 @@ pub fn inject(
     // the prelude.
     let name = names[0];
 
-    let span = DUMMY_SP.fresh_expansion(ExpnId::root(), ExpnInfo::allow_unstable(
+    let span = DUMMY_SP.fresh_expansion(ExpnData::allow_unstable(
         ExpnKind::Macro(MacroKind::Attr, sym::std_inject), DUMMY_SP, edition,
         [sym::prelude_import][..].into(),
     ));
@@ -66,7 +66,7 @@ pub fn inject(
         vis: respan(span.shrink_to_lo(), ast::VisibilityKind::Inherited),
         node: ast::ItemKind::Use(P(ast::UseTree {
             prefix: ast::Path {
-                segments: iter::once(ast::Ident::with_empty_ctxt(kw::PathRoot))
+                segments: iter::once(ast::Ident::with_dummy_span(kw::PathRoot))
                     .chain(
                         [name, "prelude", "v1"].iter().cloned()
                             .map(ast::Ident::from_str)

src/libsyntax_ext/test.rs

@@ -29,7 +29,7 @@ pub fn expand_test_case(
 
     if !ecx.ecfg.should_test { return vec![]; }
 
-    let sp = attr_sp.with_ctxt(SyntaxContext::empty().apply_mark(ecx.current_expansion.id));
+    let sp = attr_sp.with_ctxt(SyntaxContext::root().apply_mark(ecx.current_expansion.id));
     let mut item = anno_item.expect_item();
     item = item.map(|mut item| {
         item.vis = respan(item.vis.span, ast::VisibilityKind::Public);
@@ -93,7 +93,7 @@ pub fn expand_test_or_bench(
         return vec![Annotatable::Item(item)];
     }
 
-    let ctxt = SyntaxContext::empty().apply_mark(cx.current_expansion.id);
+    let ctxt = SyntaxContext::root().apply_mark(cx.current_expansion.id);
     let (sp, attr_sp) = (item.span.with_ctxt(ctxt), attr_sp.with_ctxt(ctxt));
 
     // Gensym "test" so we can extern crate without conflicting with any local names

src/libsyntax_ext/test_harness.rs

@@ -5,14 +5,13 @@ use smallvec::{smallvec, SmallVec};
 use syntax::ast::{self, Ident};
 use syntax::attr;
 use syntax::entry::{self, EntryPointType};
-use syntax::ext::base::{ExtCtxt, Resolver};
+use syntax::ext::base::{ExtCtxt, MacroKind, Resolver};
 use syntax::ext::expand::{AstFragment, ExpansionConfig};
-use syntax::ext::hygiene::{ExpnId, MacroKind};
 use syntax::feature_gate::Features;
 use syntax::mut_visit::{*, ExpectOne};
 use syntax::parse::ParseSess;
 use syntax::ptr::P;
-use syntax::source_map::{ExpnInfo, ExpnKind, dummy_spanned};
+use syntax::source_map::{ExpnData, ExpnKind, dummy_spanned};
 use syntax::symbol::{kw, sym, Symbol};
 use syntax_pos::{Span, DUMMY_SP};
 
@@ -150,7 +149,7 @@ impl MutVisitor for EntryPointCleaner {
             EntryPointType::MainAttr |
             EntryPointType::Start =>
                 item.map(|ast::Item {id, ident, attrs, node, vis, span, tokens}| {
-                    let allow_ident = Ident::with_empty_ctxt(sym::allow);
+                    let allow_ident = Ident::with_dummy_span(sym::allow);
                     let dc_nested = attr::mk_nested_word_item(Ident::from_str("dead_code"));
                     let allow_dead_code_item = attr::mk_list_item(allow_ident, vec![dc_nested]);
                     let allow_dead_code = attr::mk_attr_outer(allow_dead_code_item);
@@ -191,7 +190,7 @@ fn mk_reexport_mod(cx: &mut TestCtxt<'_>,
                    tests: Vec<Ident>,
                    tested_submods: Vec<(Ident, Ident)>)
                    -> (P<ast::Item>, Ident) {
-    let super_ = Ident::with_empty_ctxt(kw::Super);
+    let super_ = Ident::with_dummy_span(kw::Super);
 
     let items = tests.into_iter().map(|r| {
         cx.ext_cx.item_use_simple(DUMMY_SP, dummy_spanned(ast::VisibilityKind::Public),
@@ -269,12 +268,12 @@ fn mk_main(cx: &mut TestCtxt<'_>) -> P<ast::Item> {
     //            #![main]
     //            test::test_main_static(&[..tests]);
     //        }
-    let sp = DUMMY_SP.fresh_expansion(ExpnId::root(), ExpnInfo::allow_unstable(
+    let sp = DUMMY_SP.fresh_expansion(ExpnData::allow_unstable(
         ExpnKind::Macro(MacroKind::Attr, sym::test_case), DUMMY_SP, cx.ext_cx.parse_sess.edition,
         [sym::main, sym::test, sym::rustc_attrs][..].into(),
     ));
     let ecx = &cx.ext_cx;
-    let test_id = Ident::with_empty_ctxt(sym::test);
+    let test_id = Ident::with_dummy_span(sym::test);
 
     // test::test_main_static(...)
     let mut test_runner = cx.test_runner.clone().unwrap_or(

src/libsyntax_pos/edition.rs

@@ -1,7 +1,6 @@
 use crate::symbol::{Symbol, sym};
 use std::fmt;
 use std::str::FromStr;
-use crate::GLOBALS;
 
 /// The edition of the compiler (RFC 2052)
 #[derive(Clone, Copy, Hash, PartialEq, PartialOrd, Debug, RustcEncodable, RustcDecodable, Eq)]
@@ -39,10 +38,6 @@ impl fmt::Display for Edition {
 }
 
 impl Edition {
-    pub fn from_session() -> Edition {
-        GLOBALS.with(|globals| globals.edition)
-    }
-
     pub fn lint_name(&self) -> &'static str {
         match *self {
             Edition::Edition2015 => "rust_2015_compatibility",

src/libsyntax_pos/hygiene.rs

@@ -13,8 +13,8 @@
 //
 // This explains why `HygieneData`, `SyntaxContext` and `ExpnId` have interfaces
 // with a certain amount of redundancy in them. For example,
-// `SyntaxContext::outer_expn_info` combines `SyntaxContext::outer` and
+// `SyntaxContext::outer_expn_data` combines `SyntaxContext::outer` and
-// `ExpnId::expn_info` so that two `HygieneData` accesses can be performed within
+// `ExpnId::expn_data` so that two `HygieneData` accesses can be performed within
 // a single `HygieneData::with` call.
 //
 // It also explains why many functions appear in `HygieneData` and again in
@@ -56,16 +56,6 @@ struct SyntaxContextData {
 #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
 pub struct ExpnId(u32);
 
-// FIXME: Find a way to merge this with `ExpnInfo`.
-#[derive(Debug)]
-struct InternalExpnData {
-    parent: ExpnId,
-    /// Each expansion should have an associated expansion info, but sometimes there's a delay
-    /// between creation of an expansion ID and obtaining its info (e.g. macros are collected
-    /// first and then resolved later), so we use an `Option` here.
-    expn_info: Option<ExpnInfo>,
-}
-
 /// A property of a macro expansion that determines how identifiers
 /// produced by that expansion are resolved.
 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Hash, Debug, RustcEncodable, RustcDecodable)]
@@ -86,8 +76,8 @@ pub enum Transparency {
 }
 
 impl ExpnId {
-    pub fn fresh(parent: ExpnId, expn_info: Option<ExpnInfo>) -> Self {
+    pub fn fresh(expn_data: Option<ExpnData>) -> Self {
-        HygieneData::with(|data| data.fresh_expn(parent, expn_info))
+        HygieneData::with(|data| data.fresh_expn(expn_data))
     }
 
     /// The ID of the theoretical expansion that generates freshly parsed, unexpanded AST.
@@ -107,21 +97,16 @@ impl ExpnId {
     }
 
     #[inline]
-    pub fn parent(self) -> ExpnId {
+    pub fn expn_data(self) -> ExpnData {
-        HygieneData::with(|data| data.parent_expn(self))
+        HygieneData::with(|data| data.expn_data(self).clone())
     }
 
     #[inline]
-    pub fn expn_info(self) -> Option<ExpnInfo> {
+    pub fn set_expn_data(self, expn_data: ExpnData) {
-        HygieneData::with(|data| data.expn_info(self).cloned())
-    }
-
-    #[inline]
-    pub fn set_expn_info(self, info: ExpnInfo) {
         HygieneData::with(|data| {
-            let old_info = &mut data.expn_data[self.0 as usize].expn_info;
+            let old_expn_data = &mut data.expn_data[self.0 as usize];
-            assert!(old_info.is_none(), "expansion info is reset for an expansion ID");
+            assert!(old_expn_data.is_none(), "expansion data is reset for an expansion ID");
-            *old_info = Some(info);
+            *old_expn_data = Some(expn_data);
         })
     }
 
@@ -139,12 +124,9 @@ impl ExpnId {
     #[inline]
     pub fn looks_like_proc_macro_derive(self) -> bool {
         HygieneData::with(|data| {
-            if data.default_transparency(self) == Transparency::Opaque {
+            let expn_data = data.expn_data(self);
-                if let Some(expn_info) = data.expn_info(self) {
+            if let ExpnKind::Macro(MacroKind::Derive, _) = expn_data.kind {
-                    if let ExpnKind::Macro(MacroKind::Derive, _) = expn_info.kind {
+                return expn_data.default_transparency == Transparency::Opaque;
-                        return true;
-                    }
-                }
             }
             false
         })
@@ -153,7 +135,10 @@ impl ExpnId {
 
 #[derive(Debug)]
 crate struct HygieneData {
-    expn_data: Vec<InternalExpnData>,
+    /// Each expansion should have an associated expansion data, but sometimes there's a delay
+    /// between creation of an expansion ID and obtaining its data (e.g. macros are collected
+    /// first and then resolved later), so we use an `Option` here.
+    expn_data: Vec<Option<ExpnData>>,
     syntax_context_data: Vec<SyntaxContextData>,
     syntax_context_map: FxHashMap<(SyntaxContext, ExpnId, Transparency), SyntaxContext>,
 }
@@ -161,10 +146,7 @@ crate struct HygieneData {
 impl HygieneData {
     crate fn new(edition: Edition) -> Self {
         HygieneData {
-            expn_data: vec![InternalExpnData {
+            expn_data: vec![Some(ExpnData::default(ExpnKind::Root, DUMMY_SP, edition))],
-                parent: ExpnId::root(),
-                expn_info: Some(ExpnInfo::default(ExpnKind::Root, DUMMY_SP, edition)),
-            }],
             syntax_context_data: vec![SyntaxContextData {
                 outer_expn: ExpnId::root(),
                 outer_transparency: Transparency::Opaque,
@@ -181,25 +163,14 @@ impl HygieneData {
         GLOBALS.with(|globals| f(&mut *globals.hygiene_data.borrow_mut()))
     }
 
-    fn fresh_expn(&mut self, parent: ExpnId, expn_info: Option<ExpnInfo>) -> ExpnId {
+    fn fresh_expn(&mut self, expn_data: Option<ExpnData>) -> ExpnId {
-        self.expn_data.push(InternalExpnData { parent, expn_info });
+        self.expn_data.push(expn_data);
         ExpnId(self.expn_data.len() as u32 - 1)
     }
 
-    fn parent_expn(&self, expn_id: ExpnId) -> ExpnId {
+    fn expn_data(&self, expn_id: ExpnId) -> &ExpnData {
-        self.expn_data[expn_id.0 as usize].parent
+        self.expn_data[expn_id.0 as usize].as_ref()
-    }
+            .expect("no expansion data for an expansion ID")
-
-    fn expn_info(&self, expn_id: ExpnId) -> Option<&ExpnInfo> {
-        if expn_id != ExpnId::root() {
-            Some(self.expn_data[expn_id.0 as usize].expn_info.as_ref()
-                     .expect("no expansion info for an expansion ID"))
-        } else {
-            // FIXME: Some code relies on `expn_info().is_none()` meaning "no expansion".
-            // Introduce a method for checking for "no expansion" instead and always return
-            // `ExpnInfo` from this function instead of the `Option`.
-            None
-        }
     }
 
     fn is_descendant_of(&self, mut expn_id: ExpnId, ancestor: ExpnId) -> bool {
@@ -207,17 +178,11 @@ impl HygieneData {
             if expn_id == ExpnId::root() {
                 return false;
             }
-            expn_id = self.parent_expn(expn_id);
+            expn_id = self.expn_data(expn_id).parent;
         }
         true
     }
 
-    fn default_transparency(&self, expn_id: ExpnId) -> Transparency {
-        self.expn_info(expn_id).map_or(
-            Transparency::SemiTransparent, |einfo| einfo.default_transparency
-        )
-    }
-
     fn modern(&self, ctxt: SyntaxContext) -> SyntaxContext {
         self.syntax_context_data[ctxt.0 as usize].opaque
     }
@@ -246,7 +211,7 @@ impl HygieneData {
 
     fn marks(&self, mut ctxt: SyntaxContext) -> Vec<(ExpnId, Transparency)> {
         let mut marks = Vec::new();
-        while ctxt != SyntaxContext::empty() {
+        while ctxt != SyntaxContext::root() {
             marks.push((self.outer_expn(ctxt), self.outer_transparency(ctxt)));
             ctxt = self.parent_ctxt(ctxt);
         }
@@ -255,12 +220,8 @@ impl HygieneData {
     }
 
     fn walk_chain(&self, mut span: Span, to: SyntaxContext) -> Span {
-        while span.ctxt() != crate::NO_EXPANSION && span.ctxt() != to {
+        while span.from_expansion() && span.ctxt() != to {
-            if let Some(info) = self.expn_info(self.outer_expn(span.ctxt())) {
+            span = self.expn_data(self.outer_expn(span.ctxt())).call_site;
-                span = info.call_site;
-            } else {
-                break;
-            }
         }
         span
     }
@@ -275,7 +236,9 @@ impl HygieneData {
 
     fn apply_mark(&mut self, ctxt: SyntaxContext, expn_id: ExpnId) -> SyntaxContext {
         assert_ne!(expn_id, ExpnId::root());
-        self.apply_mark_with_transparency(ctxt, expn_id, self.default_transparency(expn_id))
+        self.apply_mark_with_transparency(
+            ctxt, expn_id, self.expn_data(expn_id).default_transparency
+        )
     }
 
     fn apply_mark_with_transparency(&mut self, ctxt: SyntaxContext, expn_id: ExpnId,
@@ -285,15 +248,14 @@ impl HygieneData {
             return self.apply_mark_internal(ctxt, expn_id, transparency);
         }
 
-        let call_site_ctxt =
+        let call_site_ctxt = self.expn_data(expn_id).call_site.ctxt();
-            self.expn_info(expn_id).map_or(SyntaxContext::empty(), |info| info.call_site.ctxt());
         let mut call_site_ctxt = if transparency == Transparency::SemiTransparent {
             self.modern(call_site_ctxt)
         } else {
             self.modern_and_legacy(call_site_ctxt)
         };
 
-        if call_site_ctxt == SyntaxContext::empty() {
+        if call_site_ctxt == SyntaxContext::root() {
             return self.apply_mark_internal(ctxt, expn_id, transparency);
         }
 
@@ -400,7 +362,7 @@ pub fn update_dollar_crate_names(mut get_name: impl FnMut(SyntaxContext) -> Symb
 
 impl SyntaxContext {
     #[inline]
-    pub const fn empty() -> Self {
+    pub const fn root() -> Self {
         SyntaxContext(0)
     }
 
@@ -578,20 +540,20 @@ impl SyntaxContext {
         HygieneData::with(|data| data.outer_expn(self))
     }
 
-    /// `ctxt.outer_expn_info()` is equivalent to but faster than
+    /// `ctxt.outer_expn_data()` is equivalent to but faster than
-    /// `ctxt.outer_expn().expn_info()`.
+    /// `ctxt.outer_expn().expn_data()`.
     #[inline]
-    pub fn outer_expn_info(self) -> Option<ExpnInfo> {
+    pub fn outer_expn_data(self) -> ExpnData {
-        HygieneData::with(|data| data.expn_info(data.outer_expn(self)).cloned())
+        HygieneData::with(|data| data.expn_data(data.outer_expn(self)).clone())
     }
 
-    /// `ctxt.outer_expn_with_info()` is equivalent to but faster than
+    /// `ctxt.outer_expn_with_data()` is equivalent to but faster than
-    /// `{ let outer = ctxt.outer_expn(); (outer, outer.expn_info()) }`.
+    /// `{ let outer = ctxt.outer_expn(); (outer, outer.expn_data()) }`.
     #[inline]
-    pub fn outer_expn_with_info(self) -> (ExpnId, Option<ExpnInfo>) {
+    pub fn outer_expn_with_data(self) -> (ExpnId, ExpnData) {
         HygieneData::with(|data| {
             let outer = data.outer_expn(self);
-            (outer, data.expn_info(outer).cloned())
+            (outer, data.expn_data(outer).clone())
         })
     }
 
@@ -612,10 +574,10 @@ impl Span {
     /// other compiler-generated code to set per-span properties like allowed unstable features.
     /// The returned span belongs to the created expansion and has the new properties,
     /// but its location is inherited from the current span.
-    pub fn fresh_expansion(self, parent: ExpnId, expn_info: ExpnInfo) -> Span {
+    pub fn fresh_expansion(self, expn_data: ExpnData) -> Span {
         HygieneData::with(|data| {
-            let expn_id = data.fresh_expn(parent, Some(expn_info));
+            let expn_id = data.fresh_expn(Some(expn_data));
-            self.with_ctxt(data.apply_mark(SyntaxContext::empty(), expn_id))
+            self.with_ctxt(data.apply_mark(SyntaxContext::root(), expn_id))
         })
     }
 }
@@ -623,8 +585,12 @@ impl Span {
 /// A subset of properties from both macro definition and macro call available through global data.
 /// Avoid using this if you have access to the original definition or call structures.
 #[derive(Clone, Debug, RustcEncodable, RustcDecodable)]
-pub struct ExpnInfo {
+pub struct ExpnData {
     // --- The part unique to each expansion.
+    /// The kind of this expansion - macro or compiler desugaring.
+    pub kind: ExpnKind,
+    /// The expansion that produced this expansion.
+    pub parent: ExpnId,
     /// The location of the actual macro invocation or syntax sugar , e.g.
     /// `let x = foo!();` or `if let Some(y) = x {}`
     ///
@@ -632,18 +598,18 @@ pub struct ExpnInfo {
     /// `foo!()` invoked `bar!()` internally, and there was an
     /// expression inside `bar!`; the call_site of the expression in
     /// the expansion would point to the `bar!` invocation; that
-    /// call_site span would have its own ExpnInfo, with the call_site
+    /// call_site span would have its own ExpnData, with the call_site
     /// pointing to the `foo!` invocation.
     pub call_site: Span,
-    /// The kind of this expansion - macro or compiler desugaring.
-    pub kind: ExpnKind,
 
     // --- The part specific to the macro/desugaring definition.
-    // --- FIXME: Share it between expansions with the same definition.
+    // --- It may be reasonable to share this part between expansions with the same definition,
+    // --- but such sharing is known to bring some minor inconveniences without also bringing
+    // --- noticeable perf improvements (PR #62898).
     /// The span of the macro definition (possibly dummy).
     /// This span serves only informational purpose and is not used for resolution.
     pub def_site: Span,
-    /// Transparency used by `apply_mark` for the expansion with this expansion info by default.
+    /// Transparency used by `apply_mark` for the expansion with this expansion data by default.
     pub default_transparency: Transparency,
     /// List of #[unstable]/feature-gated features that the macro is allowed to use
     /// internally without forcing the whole crate to opt-in
@@ -659,12 +625,13 @@ pub struct ExpnInfo {
     pub edition: Edition,
 }
 
-impl ExpnInfo {
+impl ExpnData {
-    /// Constructs an expansion info with default properties.
+    /// Constructs expansion data with default properties.
-    pub fn default(kind: ExpnKind, call_site: Span, edition: Edition) -> ExpnInfo {
+    pub fn default(kind: ExpnKind, call_site: Span, edition: Edition) -> ExpnData {
-        ExpnInfo {
+        ExpnData {
-            call_site,
             kind,
+            parent: ExpnId::root(),
+            call_site,
             def_site: DUMMY_SP,
             default_transparency: Transparency::SemiTransparent,
             allow_internal_unstable: None,
@@ -675,12 +642,17 @@ impl ExpnInfo {
     }
 
     pub fn allow_unstable(kind: ExpnKind, call_site: Span, edition: Edition,
-                          allow_internal_unstable: Lrc<[Symbol]>) -> ExpnInfo {
+                          allow_internal_unstable: Lrc<[Symbol]>) -> ExpnData {
-        ExpnInfo {
+        ExpnData {
             allow_internal_unstable: Some(allow_internal_unstable),
-            ..ExpnInfo::default(kind, call_site, edition)
+            ..ExpnData::default(kind, call_site, edition)
         }
     }
+
+    #[inline]
+    pub fn is_root(&self) -> bool {
+        if let ExpnKind::Root = self.kind { true } else { false }
+    }
 }
 
 /// Expansion kind.
@@ -767,6 +739,18 @@ impl DesugaringKind {
     }
 }
 
+impl Encodable for ExpnId {
+    fn encode<E: Encoder>(&self, _: &mut E) -> Result<(), E::Error> {
+        Ok(()) // FIXME(jseyfried) intercrate hygiene
+    }
+}
+
+impl Decodable for ExpnId {
+    fn decode<D: Decoder>(_: &mut D) -> Result<Self, D::Error> {
+        Ok(ExpnId::root()) // FIXME(jseyfried) intercrate hygiene
+    }
+}
+
 impl Encodable for SyntaxContext {
     fn encode<E: Encoder>(&self, _: &mut E) -> Result<(), E::Error> {
         Ok(()) // FIXME(jseyfried) intercrate hygiene
@@ -774,7 +758,7 @@ impl Encodable for SyntaxContext {
 }
 
 impl Decodable for SyntaxContext {
-    fn decode<D: Decoder>(_: &mut D) -> Result<SyntaxContext, D::Error> {
+    fn decode<D: Decoder>(_: &mut D) -> Result<Self, D::Error> {
-        Ok(SyntaxContext::empty()) // FIXME(jseyfried) intercrate hygiene
+        Ok(SyntaxContext::root()) // FIXME(jseyfried) intercrate hygiene
     }
 }

src/libsyntax_pos/lib.rs

@@ -21,7 +21,7 @@ use rustc_serialize::{Encodable, Decodable, Encoder, Decoder};
 pub mod edition;
 use edition::Edition;
 pub mod hygiene;
-pub use hygiene::{ExpnId, SyntaxContext, ExpnInfo, ExpnKind, MacroKind, DesugaringKind};
+pub use hygiene::{ExpnId, SyntaxContext, ExpnData, ExpnKind, MacroKind, DesugaringKind};
 
 mod span_encoding;
 pub use span_encoding::{Span, DUMMY_SP};
@@ -49,7 +49,6 @@ pub struct Globals {
     symbol_interner: Lock<symbol::Interner>,
     span_interner: Lock<span_encoding::SpanInterner>,
     hygiene_data: Lock<hygiene::HygieneData>,
-    edition: Edition,
 }
 
 impl Globals {
@@ -58,7 +57,6 @@ impl Globals {
             symbol_interner: Lock::new(symbol::Interner::fresh()),
             span_interner: Lock::new(span_encoding::SpanInterner::default()),
             hygiene_data: Lock::new(hygiene::HygieneData::new(edition)),
-            edition,
         }
     }
 }
@@ -288,6 +286,17 @@ impl Span {
         span.lo.0 == 0 && span.hi.0 == 0
     }
 
+    /// Returns `true` if this span comes from a macro or desugaring.
+    #[inline]
+    pub fn from_expansion(self) -> bool {
+        self.ctxt() != SyntaxContext::root()
+    }
+
+    #[inline]
+    pub fn with_root_ctxt(lo: BytePos, hi: BytePos) -> Span {
+        Span::new(lo, hi, SyntaxContext::root())
+    }
+
     /// Returns a new span representing an empty span at the beginning of this span
     #[inline]
     pub fn shrink_to_lo(self) -> Span {
@@ -344,20 +353,20 @@ impl Span {
     /// Returns the source span -- this is either the supplied span, or the span for
     /// the macro callsite that expanded to it.
     pub fn source_callsite(self) -> Span {
-        self.ctxt().outer_expn_info().map(|info| info.call_site.source_callsite()).unwrap_or(self)
+        let expn_data = self.ctxt().outer_expn_data();
+        if !expn_data.is_root() { expn_data.call_site.source_callsite() } else { self }
     }
 
     /// The `Span` for the tokens in the previous macro expansion from which `self` was generated,
     /// if any.
     pub fn parent(self) -> Option<Span> {
-        self.ctxt().outer_expn_info().map(|i| i.call_site)
+        let expn_data = self.ctxt().outer_expn_data();
+        if !expn_data.is_root() { Some(expn_data.call_site) } else { None }
     }
 
     /// Edition of the crate from which this span came.
     pub fn edition(self) -> edition::Edition {
-        self.ctxt().outer_expn_info().map_or_else(|| {
+        self.ctxt().outer_expn_data().edition
-            Edition::from_session()
-        }, |einfo| einfo.edition)
     }
 
     #[inline]
@@ -373,52 +382,42 @@ impl Span {
     /// Returns the source callee.
     ///
     /// Returns `None` if the supplied span has no expansion trace,
-    /// else returns the `ExpnInfo` for the macro definition
+    /// else returns the `ExpnData` for the macro definition
     /// corresponding to the source callsite.
-    pub fn source_callee(self) -> Option<ExpnInfo> {
+    pub fn source_callee(self) -> Option<ExpnData> {
-        fn source_callee(info: ExpnInfo) -> ExpnInfo {
+        fn source_callee(expn_data: ExpnData) -> ExpnData {
-            match info.call_site.ctxt().outer_expn_info() {
+            let next_expn_data = expn_data.call_site.ctxt().outer_expn_data();
-                Some(info) => source_callee(info),
+            if !next_expn_data.is_root() { source_callee(next_expn_data) } else { expn_data }
-                None => info,
-            }
         }
-        self.ctxt().outer_expn_info().map(source_callee)
+        let expn_data = self.ctxt().outer_expn_data();
+        if !expn_data.is_root() { Some(source_callee(expn_data)) } else { None }
     }
 
     /// Checks if a span is "internal" to a macro in which `#[unstable]`
     /// items can be used (that is, a macro marked with
     /// `#[allow_internal_unstable]`).
     pub fn allows_unstable(&self, feature: Symbol) -> bool {
-        match self.ctxt().outer_expn_info() {
+        self.ctxt().outer_expn_data().allow_internal_unstable.map_or(false, |features| {
-            Some(info) => info
+            features.iter().any(|&f| {
-                .allow_internal_unstable
+                f == feature || f == sym::allow_internal_unstable_backcompat_hack
-                .map_or(false, |features| features.iter().any(|&f|
+            })
-                    f == feature || f == sym::allow_internal_unstable_backcompat_hack
+        })
-                )),
-            None => false,
-        }
     }
 
     /// Checks if this span arises from a compiler desugaring of kind `kind`.
     pub fn is_desugaring(&self, kind: DesugaringKind) -> bool {
-        match self.ctxt().outer_expn_info() {
+        match self.ctxt().outer_expn_data().kind {
-            Some(info) => match info.kind {
+            ExpnKind::Desugaring(k) => k == kind,
-                ExpnKind::Desugaring(k) => k == kind,
+            _ => false,
-                _ => false,
-            },
-            None => false,
         }
     }
 
     /// Returns the compiler desugaring that created this span, or `None`
     /// if this span is not from a desugaring.
     pub fn desugaring_kind(&self) -> Option<DesugaringKind> {
-        match self.ctxt().outer_expn_info() {
+        match self.ctxt().outer_expn_data().kind {
-            Some(info) => match info.kind {
+            ExpnKind::Desugaring(k) => Some(k),
-                ExpnKind::Desugaring(k) => Some(k),
+            _ => None
-                _ => None
-            },
-            None => None
         }
     }
 
@@ -426,19 +425,20 @@ impl Span {
     /// can be used without triggering the `unsafe_code` lint
     //  (that is, a macro marked with `#[allow_internal_unsafe]`).
     pub fn allows_unsafe(&self) -> bool {
-        match self.ctxt().outer_expn_info() {
+        self.ctxt().outer_expn_data().allow_internal_unsafe
-            Some(info) => info.allow_internal_unsafe,
-            None => false,
-        }
     }
 
     pub fn macro_backtrace(mut self) -> Vec<MacroBacktrace> {
         let mut prev_span = DUMMY_SP;
         let mut result = vec![];
-        while let Some(info) = self.ctxt().outer_expn_info() {
+        loop {
+            let expn_data = self.ctxt().outer_expn_data();
+            if expn_data.is_root() {
+                break;
+            }
             // Don't print recursive invocations.
-            if !info.call_site.source_equal(&prev_span) {
+            if !expn_data.call_site.source_equal(&prev_span) {
-                let (pre, post) = match info.kind {
+                let (pre, post) = match expn_data.kind {
                     ExpnKind::Root => break,
                     ExpnKind::Desugaring(..) => ("desugaring of ", ""),
                     ExpnKind::Macro(macro_kind, _) => match macro_kind {
@@ -448,14 +448,14 @@ impl Span {
                     }
                 };
                 result.push(MacroBacktrace {
-                    call_site: info.call_site,
+                    call_site: expn_data.call_site,
-                    macro_decl_name: format!("{}{}{}", pre, info.kind.descr(), post),
+                    macro_decl_name: format!("{}{}{}", pre, expn_data.kind.descr(), post),
-                    def_site_span: info.def_site,
+                    def_site_span: expn_data.def_site,
                 });
             }
 
             prev_span = self;
-            self = info.call_site;
+            self = expn_data.call_site;
         }
         result
     }
@@ -468,9 +468,9 @@ impl Span {
         // Return the macro span on its own to avoid weird diagnostic output. It is preferable to
         // have an incomplete span than a completely nonsensical one.
         if span_data.ctxt != end_data.ctxt {
-            if span_data.ctxt == SyntaxContext::empty() {
+            if span_data.ctxt == SyntaxContext::root() {
                 return end;
-            } else if end_data.ctxt == SyntaxContext::empty() {
+            } else if end_data.ctxt == SyntaxContext::root() {
                 return self;
             }
             // Both spans fall within a macro.
@@ -479,7 +479,7 @@ impl Span {
         Span::new(
             cmp::min(span_data.lo, end_data.lo),
             cmp::max(span_data.hi, end_data.hi),
-            if span_data.ctxt == SyntaxContext::empty() { end_data.ctxt } else { span_data.ctxt },
+            if span_data.ctxt == SyntaxContext::root() { end_data.ctxt } else { span_data.ctxt },
         )
     }
 
@@ -490,7 +490,7 @@ impl Span {
         Span::new(
             span.hi,
             end.lo,
-            if end.ctxt == SyntaxContext::empty() { end.ctxt } else { span.ctxt },
+            if end.ctxt == SyntaxContext::root() { end.ctxt } else { span.ctxt },
         )
     }
 
@@ -501,7 +501,7 @@ impl Span {
         Span::new(
             span.lo,
             end.lo,
-            if end.ctxt == SyntaxContext::empty() { end.ctxt } else { span.ctxt },
+            if end.ctxt == SyntaxContext::root() { end.ctxt } else { span.ctxt },
         )
     }
 
@@ -611,7 +611,7 @@ impl rustc_serialize::UseSpecializedDecodable for Span {
         d.read_struct("Span", 2, |d| {
             let lo = d.read_struct_field("lo", 0, Decodable::decode)?;
             let hi = d.read_struct_field("hi", 1, Decodable::decode)?;
-            Ok(Span::new(lo, hi, NO_EXPANSION))
+            Ok(Span::with_root_ctxt(lo, hi))
         })
     }
 }
@@ -755,8 +755,6 @@ impl From<Vec<Span>> for MultiSpan {
     }
 }
 
-pub const NO_EXPANSION: SyntaxContext = SyntaxContext::empty();
-
 /// Identifies an offset of a multi-byte character in a `SourceFile`.
 #[derive(Copy, Clone, RustcEncodable, RustcDecodable, Eq, PartialEq, Debug)]
 pub struct MultiByteChar {

src/libsyntax_pos/symbol.rs

@@ -14,7 +14,6 @@ use std::fmt;
 use std::hash::{Hash, Hasher};
 use std::str;
 
-use crate::hygiene::SyntaxContext;
 use crate::{Span, DUMMY_SP, GLOBALS};
 
 #[cfg(test)]
@@ -745,25 +744,25 @@ impl Ident {
         Ident { name, span }
     }
 
-    /// Constructs a new identifier with an empty syntax context.
+    /// Constructs a new identifier with a dummy span.
     #[inline]
-    pub const fn with_empty_ctxt(name: Symbol) -> Ident {
+    pub const fn with_dummy_span(name: Symbol) -> Ident {
         Ident::new(name, DUMMY_SP)
     }
 
     #[inline]
     pub fn invalid() -> Ident {
-        Ident::with_empty_ctxt(kw::Invalid)
+        Ident::with_dummy_span(kw::Invalid)
     }
 
     /// Maps an interned string to an identifier with an empty syntax context.
     pub fn from_interned_str(string: InternedString) -> Ident {
-        Ident::with_empty_ctxt(string.as_symbol())
+        Ident::with_dummy_span(string.as_symbol())
     }
 
     /// Maps a string to an identifier with an empty span.
     pub fn from_str(string: &str) -> Ident {
-        Ident::with_empty_ctxt(Symbol::intern(string))
+        Ident::with_dummy_span(Symbol::intern(string))
     }
 
     /// Maps a string and a span to an identifier.
@@ -851,7 +850,7 @@ impl fmt::Display for Ident {
 
 impl Encodable for Ident {
     fn encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
-        if self.span.ctxt().modern() == SyntaxContext::empty() {
+        if !self.span.modern().from_expansion() {
             s.emit_str(&self.as_str())
         } else { // FIXME(jseyfried): intercrate hygiene
             let mut string = "#".to_owned();

src/libunwind/Cargo.toml

@@ -22,7 +22,7 @@ compiler_builtins = "0.1.0"
 cfg-if = "0.1.8"
 
 [build-dependencies]
-cc = { optional = true, version = "1.0.1" }
+cc = { version = "1.0.1" }
 
 [features]
-llvm-libunwind = ["cc"]
+llvm-libunwind = []

src/libunwind/build.rs

@@ -5,14 +5,14 @@ fn main() {
     let target = env::var("TARGET").expect("TARGET was not set");
 
     if cfg!(feature = "llvm-libunwind") &&
-        (target.contains("linux") ||
+        ((target.contains("linux") && !target.contains("musl")) ||
          target.contains("fuchsia")) {
         // Build the unwinding from libunwind C/C++ source code.
-        #[cfg(feature = "llvm-libunwind")]
         llvm_libunwind::compile();
     } else if target.contains("linux") {
         if target.contains("musl") {
-            // musl is handled in lib.rs
+            // linking for musl is handled in lib.rs
+            llvm_libunwind::compile();
         } else if !target.contains("android") {
             println!("cargo:rustc-link-lib=gcc_s");
         }
@@ -44,7 +44,6 @@ fn main() {
     }
 }
 
-#[cfg(feature = "llvm-libunwind")]
 mod llvm_libunwind {
     use std::env;
     use std::path::Path;
@@ -96,6 +95,15 @@ mod llvm_libunwind {
             cfg.file(root.join("src").join(src));
         }
 
+        if target_env == "musl" {
+            // use the same C compiler command to compile C++ code so we do not need to setup the
+            // C++ compiler env variables on the builders
+            cfg.cpp(false);
+            // linking for musl is handled in lib.rs
+            cfg.cargo_metadata(false);
+            println!("cargo:rustc-link-search=native={}", env::var("OUT_DIR").unwrap());
+        }
+
         cfg.compile("unwind");
     }
 }