Add Array Impl Lang Item in various places

Add basic test

And also run fmt which is where the other changes are from

Fix mut issues

These only appear when running tests, so resolved by adding mut

Author: JulianKnodt

library/core/src/array/mod.rs

@@ -377,7 +377,7 @@ impl<T, const N: usize> [T; N] {
     /// assert_eq!(y, [2,3,4]);
     /// ```
     #[unstable(feature = "array_map", issue = "77777")]
-    fn map<F, S>(self, f: F) -> [S; N]
+    fn map<F, S>(self, mut f: F) -> [S; N]
     where
         F: FnMut(T) -> S,
     {
@@ -406,14 +406,16 @@ impl<T, const N: usize> [T; N] {
                 }
             }
         }
-        let dst = MaybeUninit::uninit_array::<N>();
+        let mut dst = MaybeUninit::uninit_array::<N>();
         let mut guard = Guard::new(&mut dst);
-        for (i, e) in self.into_iter().enumerate() {
+        for (i, e) in IntoIter::new(self).enumerate() {
             dst[i] = MaybeUninit::new(f(e));
             guard.curr_init += 1;
         }
         // FIXME convert to crate::mem::transmute when works with generics
         // unsafe { crate::mem::transmute::<[MaybeUninit<S>; N], [S; N]>(dst) }
-        unsafe { (&mut dst as *mut _ as *mut [S; N]).read() }
+        let mapped = unsafe { (&mut dst as *mut _ as *mut [S; N]).read() };
+        crate::mem::forget(guard);
+        mapped
     }
 }

library/core/tests/array.rs

@@ -290,3 +290,10 @@ fn empty_array_is_always_default() {
 
     let _arr = <[DoesNotImplDefault; 0]>::default();
 }
+
+#[test]
+fn array_map() {
+    let a = [1, 2, 3];
+    let b = a.map(|v| v + 1);
+    assert_eq!(b, [2, 3, 4]);
+}

src/librustc_typeck/check/method/probe.rs

@@ -649,6 +649,10 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
                     self.assemble_inherent_impl_for_primitive(lang_def_id);
                 }
             }
+            ty::Array(_, _) => {
+                let lang_def_id = lang_items.array_impl();
+                self.assemble_inherent_impl_for_primitive(lang_def_id);
+            }
             ty::RawPtr(ty::TypeAndMut { ty: _, mutbl }) => {
                 let (lang_def_id1, lang_def_id2) = match mutbl {
                     hir::Mutability::Not => {

src/librustc_typeck/coherence/inherent_impls.rs

@@ -112,6 +112,16 @@ impl ItemLikeVisitor<'v> for InherentCollect<'tcx> {
                     item.span,
                 );
             }
+            ty::Array(_, _) => {
+                self.check_primitive_impl(
+                    def_id,
+                    lang_items.array_impl(),
+                    None,
+                    "array",
+                    "[T; N]",
+                    item.span,
+                );
+            }
             ty::RawPtr(ty::TypeAndMut { ty: inner, mutbl: hir::Mutability::Not })
                 if matches!(inner.kind, ty::Slice(_)) =>
             {

src/librustdoc/clean/utils.rs

@@ -385,7 +385,7 @@ pub fn build_deref_target_impls(cx: &DocContext<'_>, items: &[Item], ret: &mut V
             Bool => tcx.lang_items().bool_impl(),
             Str => tcx.lang_items().str_impl(),
             Slice => tcx.lang_items().slice_impl(),
-            Array => tcx.lang_items().slice_impl(),
+            Array => tcx.lang_items().array_impl(),
             Tuple => None,
             Unit => None,
             RawPointer => tcx.lang_items().const_ptr_impl(),

src/librustdoc/passes/collect_trait_impls.rs

@@ -55,6 +55,7 @@ pub fn collect_trait_impls(krate: Crate, cx: &DocContext<'_>) -> Crate {
         lang_items.bool_impl(),
         lang_items.char_impl(),
         lang_items.str_impl(),
+        lang_items.array_impl(),
         lang_items.slice_impl(),
         lang_items.slice_u8_impl(),
         lang_items.str_alloc_impl(),