Add newtype of [u8] as "str" lang item.

Author: eddyb

src/libcore/str/mod.rs

@@ -26,6 +26,11 @@ pub mod pattern;
 #[allow(missing_docs)]
 pub mod lossy;
 
+// HACK(eddyb) private and not named `str` to avoid changing name resolution.
+#[cfg(not(bootstrap))]
+#[lang = "str"]
+struct Str([u8]);
+
 /// Parse a value from a string
 ///
 /// `FromStr`'s [`from_str`] method is often used implicitly, through

src/librustc_hir/lang_items.rs

@@ -127,6 +127,7 @@ language_item_table! {
 //  Variant name,                Name,                 Method name,             Target;
     BoolImplItem,                "bool",               bool_impl,               Target::Impl;
     CharImplItem,                "char",               char_impl,               Target::Impl;
+    StrItem,                     "str",                str_type,                Target::Struct;
     StrImplItem,                 "str_impl",           str_impl,                Target::Impl;
     SliceImplItem,               "slice",              slice_impl,              Target::Impl;
     SliceU8ImplItem,             "slice_u8",           slice_u8_impl,           Target::Impl;