Add a lang item to allow impl [u8] {…} in the standard library

Author: SimonSapin

src/librustc/middle/lang_items.rs

@@ -211,6 +211,7 @@ language_item_table! {
     CharImplItem,                    "char",                    char_impl;
     StrImplItem,                     "str",                     str_impl;
     SliceImplItem,                   "slice",                   slice_impl;
+    SliceU8ImplItem,                 "slice_u8",                slice_u8_impl;
     ConstPtrImplItem,                "const_ptr",               const_ptr_impl;
     MutPtrImplItem,                  "mut_ptr",                 mut_ptr_impl;
     I8ImplItem,                      "i8",                      i8_impl;

src/librustc_typeck/check/method/probe.rs

@@ -431,6 +431,9 @@ impl<'a, 'gcx, 'tcx> ProbeContext<'a, 'gcx, 'tcx> {
             ty::TySlice(_) => {
                 let lang_def_id = lang_items.slice_impl();
                 self.assemble_inherent_impl_for_primitive(lang_def_id);
+
+                let lang_def_id = lang_items.slice_u8_impl();
+                self.assemble_inherent_impl_for_primitive(lang_def_id);
             }
             ty::TyRawPtr(ty::TypeAndMut { ty: _, mutbl: hir::MutImmutable }) => {
                 let lang_def_id = lang_items.const_ptr_impl();

src/librustc_typeck/coherence/inherent_impls.rs

@@ -137,6 +137,13 @@ impl<'a, 'tcx, 'v> ItemLikeVisitor<'v> for InherentCollect<'a, 'tcx> {
                                           "str",
                                           item.span);
             }
+            ty::TySlice(slice_item) if slice_item == self.tcx.types.u8 => {
+                self.check_primitive_impl(def_id,
+                                          lang_items.slice_u8_impl(),
+                                          "slice_u8",
+                                          "[u8]",
+                                          item.span);
+            }
             ty::TySlice(_) => {
                 self.check_primitive_impl(def_id,
                                           lang_items.slice_impl(),