Use IntoIterator for array impl everywhere.

compiler/rustc_ast_lowering/src/lib.rs

@@ -70,10 +70,9 @@ use smallvec::SmallVec;
 use tracing::{debug, trace};
 
 macro_rules! arena_vec {
-    ($this:expr; $($x:expr),*) => ({
-        let a = [$($x),*];
-        $this.arena.alloc_from_iter(std::array::IntoIter::new(a))
-    });
+    ($this:expr; $($x:expr),*) => (
+        $this.arena.alloc_from_iter([$($x),*])
+    );
 }
 
 mod asm;

compiler/rustc_codegen_cranelift/scripts/cargo.rs

@@ -42,7 +42,7 @@ fn main() {
                 "RUSTFLAGS",
                 env::var("RUSTFLAGS").unwrap_or(String::new()) + " -Cprefer-dynamic",
             );
-            std::array::IntoIter::new(["rustc".to_string()])
+            IntoIterator::into_iter(["rustc".to_string()])
                 .chain(env::args().skip(2))
                 .chain([
                     "--".to_string(),
@@ -56,7 +56,7 @@ fn main() {
                 "RUSTFLAGS",
                 env::var("RUSTFLAGS").unwrap_or(String::new()) + " -Cprefer-dynamic",
             );
-            std::array::IntoIter::new(["rustc".to_string()])
+            IntoIterator::into_iter(["rustc".to_string()])
                 .chain(env::args().skip(2))
                 .chain([
                     "--".to_string(),

compiler/rustc_expand/src/proc_macro_server.rs

@@ -466,13 +466,12 @@ impl server::TokenStream for Rustc<'_, '_> {
             ast::ExprKind::Unary(ast::UnOp::Neg, e) => match &e.kind {
                 ast::ExprKind::Lit(l) => match l.token {
                     token::Lit { kind: token::Integer | token::Float, .. } => {
-                        Ok(std::array::IntoIter::new([
+                        Ok(Self::TokenStream::from_iter([
                             // FIXME: The span of the `-` token is lost when
                             // parsing, so we cannot faithfully recover it here.
                             tokenstream::TokenTree::token(token::BinOp(token::Minus), e.span),
                             tokenstream::TokenTree::token(token::Literal(l.token), l.span),
-                        ])
-                        .collect())
+                        ]))
                     }
                     _ => Err(()),
                 },

compiler/rustc_hir/src/def.rs

@@ -443,11 +443,11 @@ impl<T> PerNS<T> {
     }
 
     pub fn into_iter(self) -> IntoIter<T, 3> {
-        IntoIter::new([self.value_ns, self.type_ns, self.macro_ns])
+        [self.value_ns, self.type_ns, self.macro_ns].into_iter()
     }
 
     pub fn iter(&self) -> IntoIter<&T, 3> {
-        IntoIter::new([&self.value_ns, &self.type_ns, &self.macro_ns])
+        [&self.value_ns, &self.type_ns, &self.macro_ns].into_iter()
     }
 }
 
@@ -481,7 +481,7 @@ impl<T> PerNS<Option<T>> {
 
     /// Returns an iterator over the items which are `Some`.
     pub fn present_items(self) -> impl Iterator<Item = T> {
-        IntoIter::new([self.type_ns, self.value_ns, self.macro_ns]).flatten()
+        [self.type_ns, self.value_ns, self.macro_ns].into_iter().flatten()
     }
 }
 

compiler/rustc_session/src/filesearch.rs

@@ -4,6 +4,7 @@ pub use self::FileMatch::*;
 
 use std::env;
 use std::fs;
+use std::iter::FromIterator;
 use std::path::{Path, PathBuf};
 
 use crate::search_paths::{PathKind, SearchPath, SearchPathFile};
@@ -91,8 +92,7 @@ impl<'a> FileSearch<'a> {
 
 pub fn make_target_lib_path(sysroot: &Path, target_triple: &str) -> PathBuf {
     let rustlib_path = rustc_target::target_rustlib_path(sysroot, target_triple);
-    std::array::IntoIter::new([sysroot, Path::new(&rustlib_path), Path::new("lib")])
-        .collect::<PathBuf>()
+    PathBuf::from_iter([sysroot, Path::new(&rustlib_path), Path::new("lib")])
 }
 
 /// This function checks if sysroot is found using env::args().next(), and if it

compiler/rustc_session/src/session.rs

@@ -795,12 +795,11 @@ impl Session {
     /// Returns a list of directories where target-specific tool binaries are located.
     pub fn get_tools_search_paths(&self, self_contained: bool) -> Vec<PathBuf> {
         let rustlib_path = rustc_target::target_rustlib_path(&self.sysroot, &config::host_triple());
-        let p = std::array::IntoIter::new([
+        let p = PathBuf::from_iter([
             Path::new(&self.sysroot),
             Path::new(&rustlib_path),
             Path::new("bin"),
-        ])
-        .collect::<PathBuf>();
+        ]);
         if self_contained { vec![p.clone(), p.join("self-contained")] } else { vec![p] }
     }
 

compiler/rustc_target/src/lib.rs

@@ -16,6 +16,7 @@
 #![feature(min_specialization)]
 #![feature(step_trait)]
 
+use std::iter::FromIterator;
 use std::path::{Path, PathBuf};
 
 #[macro_use]
@@ -47,12 +48,11 @@ const RUST_LIB_DIR: &str = "rustlib";
 /// `"lib*/rustlib/x86_64-unknown-linux-gnu"`.
 pub fn target_rustlib_path(sysroot: &Path, target_triple: &str) -> PathBuf {
     let libdir = find_libdir(sysroot);
-    std::array::IntoIter::new([
+    PathBuf::from_iter([
         Path::new(libdir.as_ref()),
         Path::new(RUST_LIB_DIR),
         Path::new(target_triple),
     ])
-    .collect::<PathBuf>()
 }
 
 /// The name of the directory rustc expects libraries to be located.

compiler/rustc_target/src/spec/mod.rs

@@ -42,6 +42,7 @@ use rustc_serialize::json::{Json, ToJson};
 use rustc_span::symbol::{sym, Symbol};
 use std::collections::BTreeMap;
 use std::convert::TryFrom;
+use std::iter::FromIterator;
 use std::ops::{Deref, DerefMut};
 use std::path::{Path, PathBuf};
 use std::str::FromStr;
@@ -2173,12 +2174,11 @@ impl Target {
                 // Additionally look in the sysroot under `lib/rustlib/<triple>/target.json`
                 // as a fallback.
                 let rustlib_path = crate::target_rustlib_path(&sysroot, &target_triple);
-                let p = std::array::IntoIter::new([
+                let p = PathBuf::from_iter([
                     Path::new(sysroot),
                     Path::new(&rustlib_path),
                     Path::new("target.json"),
-                ])
-                .collect::<PathBuf>();
+                ]);
                 if p.is_file() {
                     return load_file(&p);
                 }

compiler/rustc_trait_selection/src/traits/object_safety.rs

@@ -25,7 +25,6 @@ use rustc_span::symbol::Symbol;
 use rustc_span::{MultiSpan, Span};
 use smallvec::SmallVec;
 
-use std::array;
 use std::iter;
 use std::ops::ControlFlow;
 
@@ -692,11 +691,8 @@ fn receiver_is_dispatchable<'tcx>(
                 .to_predicate(tcx)
         };
 
-        let caller_bounds: Vec<Predicate<'tcx>> = param_env
-            .caller_bounds()
-            .iter()
-            .chain(array::IntoIter::new([unsize_predicate, trait_predicate]))
-            .collect();
+        let caller_bounds: Vec<Predicate<'tcx>> =
+            param_env.caller_bounds().iter().chain([unsize_predicate, trait_predicate]).collect();
 
         ty::ParamEnv::new(tcx.intern_predicates(&caller_bounds), param_env.reveal())
     };

compiler/rustc_typeck/src/astconv/mod.rs

@@ -35,7 +35,6 @@ use rustc_trait_selection::traits::error_reporting::report_object_safety_error;
 use rustc_trait_selection::traits::wf::object_region_bounds;
 
 use smallvec::SmallVec;
-use std::array;
 use std::collections::BTreeSet;
 use std::slice;
 
@@ -1635,7 +1634,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
             debug!("one_bound_for_assoc_type: bound2 = {:?}", bound2);
 
             let is_equality = is_equality();
-            let bounds = array::IntoIter::new([bound, bound2]).chain(matching_candidates);
+            let bounds = IntoIterator::into_iter([bound, bound2]).chain(matching_candidates);
             let mut err = if is_equality.is_some() {
                 // More specific Error Index entry.
                 struct_span_err!(

compiler/rustc_typeck/src/check/wfcheck.rs

@@ -1822,7 +1822,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 // Inherent impl: take implied bounds from the `self` type.
                 let self_ty = self.tcx.type_of(impl_def_id);
                 let self_ty = self.normalize_associated_types_in(span, self_ty);
-                std::array::IntoIter::new([self_ty]).collect()
+                FxHashSet::from_iter([self_ty])
             }
         }
     }

library/alloc/src/collections/binary_heap.rs

@@ -1500,7 +1500,7 @@ impl<T: Ord, const N: usize> From<[T; N]> for BinaryHeap<T> {
     /// }
     /// ```
     fn from(arr: [T; N]) -> Self {
-        core::array::IntoIter::new(arr).collect()
+        Self::from_iter(arr)
     }
 }
 

library/alloc/src/collections/btree/map.rs

@@ -1305,11 +1305,11 @@ impl<K, V> BTreeMap<K, V> {
     pub(crate) fn bulk_build_from_sorted_iter<I>(iter: I) -> Self
     where
         K: Ord,
-        I: Iterator<Item = (K, V)>,
+        I: IntoIterator<Item = (K, V)>,
     {
         let mut root = Root::new();
         let mut length = 0;
-        root.bulk_push(DedupSortedIter::new(iter), &mut length);
+        root.bulk_push(DedupSortedIter::new(iter.into_iter()), &mut length);
         BTreeMap { root: Some(root), length }
     }
 }
@@ -1944,7 +1944,7 @@ impl<K: Ord, V> FromIterator<(K, V)> for BTreeMap<K, V> {
 
         // use stable sort to preserve the insertion order.
         inputs.sort_by(|a, b| a.0.cmp(&b.0));
-        BTreeMap::bulk_build_from_sorted_iter(inputs.into_iter())
+        BTreeMap::bulk_build_from_sorted_iter(inputs)
     }
 }
 
@@ -2061,7 +2061,7 @@ impl<K: Ord, V, const N: usize> From<[(K, V); N]> for BTreeMap<K, V> {
 
         // use stable sort to preserve the insertion order.
         arr.sort_by(|a, b| a.0.cmp(&b.0));
-        BTreeMap::bulk_build_from_sorted_iter(core::array::IntoIter::new(arr))
+        BTreeMap::bulk_build_from_sorted_iter(arr)
     }
 }
 

library/alloc/src/collections/btree/set.rs

@@ -1106,7 +1106,7 @@ impl<T: Ord, const N: usize> From<[T; N]> for BTreeSet<T> {
 
         // use stable sort to preserve the insertion order.
         arr.sort();
-        let iter = core::array::IntoIter::new(arr).map(|k| (k, ()));
+        let iter = IntoIterator::into_iter(arr).map(|k| (k, ()));
         let map = BTreeMap::bulk_build_from_sorted_iter(iter);
         BTreeSet { map }
     }

library/alloc/src/collections/linked_list.rs

@@ -1961,7 +1961,7 @@ impl<T, const N: usize> From<[T; N]> for LinkedList<T> {
     /// assert_eq!(list1, list2);
     /// ```
     fn from(arr: [T; N]) -> Self {
-        core::array::IntoIter::new(arr).collect()
+        Self::from_iter(arr)
     }
 }
 

library/core/tests/iter/adapters/flatten.rs

@@ -1,5 +1,4 @@
 use super::*;
-use core::array;
 use core::iter::*;
 
 #[test]
@@ -134,7 +133,7 @@ fn test_double_ended_flatten() {
 #[test]
 fn test_trusted_len_flatten() {
     fn assert_trusted_len<T: TrustedLen>(_: &T) {}
-    let mut iter = array::IntoIter::new([[0; 3]; 4]).flatten();
+    let mut iter = IntoIterator::into_iter([[0; 3]; 4]).flatten();
     assert_trusted_len(&iter);
 
     assert_eq!(iter.size_hint(), (12, Some(12)));
@@ -143,21 +142,21 @@ fn test_trusted_len_flatten() {
     iter.next_back();
     assert_eq!(iter.size_hint(), (10, Some(10)));
 
-    let iter = array::IntoIter::new([[(); usize::MAX]; 1]).flatten();
+    let iter = IntoIterator::into_iter([[(); usize::MAX]; 1]).flatten();
     assert_eq!(iter.size_hint(), (usize::MAX, Some(usize::MAX)));
 
-    let iter = array::IntoIter::new([[(); usize::MAX]; 2]).flatten();
+    let iter = IntoIterator::into_iter([[(); usize::MAX]; 2]).flatten();
     assert_eq!(iter.size_hint(), (usize::MAX, None));
 
     let mut a = [(); 10];
     let mut b = [(); 10];
 
-    let iter = array::IntoIter::new([&mut a, &mut b]).flatten();
+    let iter = IntoIterator::into_iter([&mut a, &mut b]).flatten();
     assert_trusted_len(&iter);
     assert_eq!(iter.size_hint(), (20, Some(20)));
     core::mem::drop(iter);
 
-    let iter = array::IntoIter::new([&a, &b]).flatten();
+    let iter = IntoIterator::into_iter([&a, &b]).flatten();
     assert_trusted_len(&iter);
     assert_eq!(iter.size_hint(), (20, Some(20)));
 

library/std/src/collections/hash/map.rs

@@ -1186,7 +1186,7 @@ where
     /// assert_eq!(map1, map2);
     /// ```
     fn from(arr: [(K, V); N]) -> Self {
-        crate::array::IntoIter::new(arr).collect()
+        Self::from_iter(arr)
     }
 }
 

library/std/src/collections/hash/set.rs

@@ -1022,7 +1022,7 @@ where
     /// assert_eq!(set1, set2);
     /// ```
     fn from(arr: [T; N]) -> Self {
-        crate::array::IntoIter::new(arr).collect()
+        Self::from_iter(arr)
     }
 }
 

src/bootstrap/lib.rs

@@ -1043,7 +1043,7 @@ impl Build {
             options[1] = Some(format!("-Clink-arg=-Wl,{}", threads));
         }
 
-        std::array::IntoIter::new(options).flatten()
+        IntoIterator::into_iter(options).flatten()
     }
 
     /// Returns if this target should statically link the C runtime, if specified

src/test/ui/proc-macro/auxiliary/custom-quote.rs

@@ -6,6 +6,7 @@
 #![crate_type = "proc-macro"]
 
 extern crate proc_macro;
+use std::iter::FromIterator;
 use std::str::FromStr;
 use proc_macro::*;
 
@@ -23,7 +24,7 @@ pub fn custom_quote(input: TokenStream) -> TokenStream {
             let set_span_method = TokenStream::from_str("ident.set_span").unwrap();
             let set_span_arg = TokenStream::from(TokenTree::Group(Group::new(Delimiter::Parenthesis, quoted_span)));
             let suffix = TokenStream::from_str(";proc_macro::TokenStream::from(proc_macro::TokenTree::Ident(ident))").unwrap();
-            let full_stream: TokenStream = std::array::IntoIter::new([prefix, set_span_method, set_span_arg, suffix]).collect();
+            let full_stream = TokenStream::from_iter([prefix, set_span_method, set_span_arg, suffix]);
             full_stream
         }
         _ => unreachable!()

src/tools/clippy/clippy_lints/src/matches.rs

@@ -13,7 +13,6 @@ use clippy_utils::{
     remove_blocks, strip_pat_refs,
 };
 use clippy_utils::{paths, search_same, SpanlessEq, SpanlessHash};
-use core::array;
 use core::iter::{once, ExactSizeIterator};
 use if_chain::if_chain;
 use rustc_ast::ast::{Attribute, LitKind};
@@ -1306,7 +1305,7 @@ fn check_match_like_matches<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>)
         return find_matches_sugg(
             cx,
             let_expr,
-            array::IntoIter::new([(&[][..], Some(let_pat), if_then, None), (&[][..], None, if_else, None)]),
+            IntoIterator::into_iter([(&[][..], Some(let_pat), if_then, None), (&[][..], None, if_else, None)]),
             expr,
             true,
         );