Remove MacroKind::ProcMacroStub

It's internal to resolve and always results in `Res::Err` outside of resolve.
Instead put `DefKind::Fn`s themselves into the macro namespace, it's ok.

Proc macro stubs are items placed into macro namespase for functions that define proc macros.
https://github.com/rust-lang/rust/pull/52383

The rustdoc test is changed because the old test didn't actually reproduce the ICE it was supposed to reproduce.

src/librustc/ich/impls_syntax.rs

@@ -89,7 +89,6 @@ impl_stable_hash_for!(enum ::syntax::ext::base::MacroKind {
     Bang,
     Attr,
     Derive,
-    ProcMacroStub,
 });
 
 

src/librustc_resolve/build_reduced_graph.rs

@@ -29,7 +29,7 @@ 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::base::SyntaxExtension;
 use syntax::ext::base::Determinacy::Undetermined;
 use syntax::ext::hygiene::Mark;
 use syntax::ext::tt::macro_rules;
@@ -46,6 +46,20 @@ use log::debug;
 
 type Res = def::Res<NodeId>;
 
+fn proc_macro_stub(item: &Item) -> Option<(Ident, Span)> {
+    if attr::contains_name(&item.attrs, sym::proc_macro) ||
+       attr::contains_name(&item.attrs, sym::proc_macro_attribute) {
+        return Some((item.ident, item.span));
+    } else if let Some(attr) = attr::find_by_name(&item.attrs, sym::proc_macro_derive) {
+        if let Some(nested_meta) = attr.meta_item_list().and_then(|list| list.get(0).cloned()) {
+            if let Some(ident) = nested_meta.ident() {
+                return Some((ident, ident.span));
+            }
+        }
+    }
+    None
+}
+
 impl<'a> ToNameBinding<'a> for (Module<'a>, ty::Visibility, Span, Mark) {
     fn to_name_binding(self, arenas: &'a ResolverArenas<'a>) -> &'a NameBinding<'a> {
         arenas.alloc_name_binding(NameBinding {
@@ -456,22 +470,8 @@ impl<'a> Resolver<'a> {
 
                 // Functions introducing procedural macros reserve a slot
                 // in the macro namespace as well (see #52225).
-                if attr::contains_name(&item.attrs, sym::proc_macro) ||
-                   attr::contains_name(&item.attrs, sym::proc_macro_attribute) {
-                    let res = Res::Def(DefKind::Macro(MacroKind::ProcMacroStub), res.def_id());
-                    self.define(parent, ident, MacroNS, (res, vis, sp, expansion));
-                }
-                if let Some(attr) = attr::find_by_name(&item.attrs, sym::proc_macro_derive) {
-                    if let Some(trait_attr) =
-                            attr.meta_item_list().and_then(|list| list.get(0).cloned()) {
-                        if let Some(ident) = trait_attr.ident() {
-                            let res = Res::Def(
-                                DefKind::Macro(MacroKind::ProcMacroStub),
-                                res.def_id(),
-                            );
-                            self.define(parent, ident, MacroNS, (res, vis, ident.span, expansion));
-                        }
-                    }
+                if let Some((ident, span)) = proc_macro_stub(item) {
+                    self.define(parent, ident, MacroNS, (res, vis, span, expansion));
                 }
             }
 
@@ -778,8 +778,6 @@ impl<'a> Resolver<'a> {
 
     crate fn opt_get_macro(&mut self, res: Res) -> Option<Lrc<SyntaxExtension>> {
         let def_id = match res {
-            Res::Def(DefKind::Macro(MacroKind::ProcMacroStub), _) =>
-                return Some(self.non_macro_attr(true)), // some dummy extension
             Res::Def(DefKind::Macro(..), def_id) => def_id,
             Res::NonMacroAttr(attr_kind) =>
                 return Some(self.non_macro_attr(attr_kind == NonMacroAttrKind::Tool)),

src/librustc_resolve/macros.rs

@@ -102,12 +102,11 @@ fn sub_namespace_match(candidate: Option<MacroKind>, requirement: Option<MacroKi
     #[derive(PartialEq)]
     enum SubNS { Bang, AttrLike }
     let sub_ns = |kind| match kind {
-        MacroKind::Bang => Some(SubNS::Bang),
-        MacroKind::Attr | MacroKind::Derive => Some(SubNS::AttrLike),
-        MacroKind::ProcMacroStub => None,
+        MacroKind::Bang => SubNS::Bang,
+        MacroKind::Attr | MacroKind::Derive => SubNS::AttrLike,
     };
-    let requirement = requirement.and_then(|kind| sub_ns(kind));
-    let candidate = candidate.and_then(|kind| sub_ns(kind));
+    let candidate = candidate.map(sub_ns);
+    let requirement = requirement.map(sub_ns);
     // "No specific sub-namespace" means "matches anything" for both requirements and candidates.
     candidate.is_none() || requirement.is_none() || candidate == requirement
 }
@@ -310,15 +309,15 @@ impl<'a> Resolver<'a> {
         let res = res?;
 
         match res {
-            Res::Def(DefKind::Macro(macro_kind), def_id) => {
+            Res::Def(DefKind::Macro(_), def_id) => {
                 if let Some(node_id) = self.definitions.as_local_node_id(def_id) {
                     self.unused_macros.remove(&node_id);
                 }
-                if macro_kind == MacroKind::ProcMacroStub {
-                    let msg = "can't use a procedural macro from the same crate that defines it";
-                    self.session.span_err(path.span, msg);
-                    return Err(Determinacy::Determined);
-                }
+            }
+            Res::Def(DefKind::Fn, _) => {
+                let msg = "can't use a procedural macro from the same crate that defines it";
+                self.session.span_err(path.span, msg);
+                return Err(Determinacy::Determined);
             }
             Res::NonMacroAttr(attr_kind) => {
                 if kind == MacroKind::Attr {

src/librustdoc/clean/mod.rs

@@ -4199,7 +4199,6 @@ pub fn register_res(cx: &DocContext<'_>, res: Res) -> DefId {
             MacroKind::Bang => (i, TypeKind::Macro),
             MacroKind::Attr => (i, TypeKind::Attr),
             MacroKind::Derive => (i, TypeKind::Derive),
-            MacroKind::ProcMacroStub => unreachable!(),
         },
         Res::Def(DefKind::TraitAlias, i) => (i, TypeKind::TraitAlias),
         Res::SelfTy(Some(def_id), _) => (def_id, TypeKind::Trait),

src/librustdoc/html/item_type.rs

@@ -92,7 +92,6 @@ impl<'a> From<&'a clean::Item> for ItemType {
                 MacroKind::Bang            => ItemType::Macro,
                 MacroKind::Attr            => ItemType::ProcAttribute,
                 MacroKind::Derive          => ItemType::ProcDerive,
-                MacroKind::ProcMacroStub   => unreachable!(),
             }
             clean::StrippedItem(..)        => unreachable!(),
         }

src/librustdoc/html/render.rs

@@ -2471,7 +2471,6 @@ impl<'a> fmt::Display for Item<'a> {
                 MacroKind::Bang => write!(fmt, "Macro ")?,
                 MacroKind::Attr => write!(fmt, "Attribute Macro ")?,
                 MacroKind::Derive => write!(fmt, "Derive Macro ")?,
-                MacroKind::ProcMacroStub => unreachable!(),
             }
             clean::PrimitiveItem(..) => write!(fmt, "Primitive Type ")?,
             clean::StaticItem(..) | clean::ForeignStaticItem(..) => write!(fmt, "Static ")?,
@@ -5092,7 +5091,6 @@ fn item_proc_macro(w: &mut fmt::Formatter<'_>, cx: &Context, it: &clean::Item, m
             }
             write!(w, "</pre>")?;
         }
-        _ => {}
     }
     document(w, cx, it)
 }

src/librustdoc/passes/collect_intra_doc_links.rs

@@ -429,15 +429,11 @@ fn macro_resolve(cx: &DocContext<'_>, path_str: &str) -> Option<Res> {
     let segment = ast::PathSegment::from_ident(Ident::from_str(path_str));
     let path = ast::Path { segments: vec![segment], span: DUMMY_SP };
     cx.enter_resolver(|resolver| {
-        let parent_scope = resolver.dummy_parent_scope();
-        if let Ok(res) = resolver.resolve_macro_to_res_inner(&path, MacroKind::Bang,
-                                                            &parent_scope, false, false) {
-            if let Res::Def(DefKind::Macro(MacroKind::ProcMacroStub), _) = res {
-                // skip proc-macro stubs, they'll cause `get_macro` to crash
-            } else {
-                if let SyntaxExtensionKind::LegacyBang(..) = resolver.get_macro(res).kind {
-                    return Some(res.map_id(|_| panic!("unexpected id")));
-                }
+        if let Ok(res @ Res::Def(DefKind::Macro(_), _)) = resolver.resolve_macro_to_res_inner(
+            &path, MacroKind::Bang, &resolver.dummy_parent_scope(), false, false
+        ) {
+            if let SyntaxExtensionKind::LegacyBang { .. } = resolver.get_macro(res).kind {
+                return Some(res.map_id(|_| panic!("unexpected id")));
             }
         }
         if let Some(res) = resolver.all_macros.get(&Symbol::intern(path_str)) {

src/librustdoc/visit_ast.rs

@@ -406,11 +406,8 @@ impl<'a, 'tcx> RustdocVisitor<'a, 'tcx> {
 
                 // Struct and variant constructors and proc macro stubs always show up alongside
                 // their definitions, we've already processed them so just discard these.
-                match path.res {
-                    Res::Def(DefKind::Ctor(..), _)
-                    | Res::SelfCtor(..)
-                    | Res::Def(DefKind::Macro(MacroKind::ProcMacroStub), _) => return,
-                    _ => {}
+                if let Res::Def(DefKind::Ctor(..), _) | Res::SelfCtor(..) = path.res {
+                    return;
                 }
 
                 // If there was a private module in the current path then don't bother inlining

src/libsyntax/ext/base.rs

@@ -527,8 +527,6 @@ pub enum MacroKind {
     Attr,
     /// A derive attribute macro - #[derive(Foo)]
     Derive,
-    /// A view of a procedural macro from the same crate that defines it.
-    ProcMacroStub,
 }
 
 impl MacroKind {
@@ -537,7 +535,6 @@ impl MacroKind {
             MacroKind::Bang => "macro",
             MacroKind::Attr => "attribute macro",
             MacroKind::Derive => "derive macro",
-            MacroKind::ProcMacroStub => "crate-local procedural macro",
         }
     }
 

src/test/rustdoc/proc-macro.rs

@@ -7,7 +7,7 @@
 // @has some_macros/index.html
 // @has - '//a/[@href="attr.some_proc_attr.html"]' 'some_proc_attr'
 
-//! include a link to [some_proc_attr] to make sure it works.
+//! include a link to [some_proc_macro] to make sure it works.
 
 extern crate proc_macro;