Auto merge of #26351 - eddyb:tls-tcx, r=nikomatsakis

Pre-requisite for splitting the type context into global and local parts.
The `Repr` and `UserString` traits were also replaced by `Debug` and `Display`.

Author: bors

src/librustc/lib.rs

@@ -51,6 +51,7 @@
 #![feature(ref_slice)]
 #![feature(rustc_diagnostic_macros)]
 #![feature(rustc_private)]
+#![feature(scoped_tls)]
 #![feature(slice_bytes)]
 #![feature(slice_extras)]
 #![feature(slice_patterns)]

src/librustc/metadata/tydecode.rs

@@ -898,7 +898,7 @@ fn parse_builtin_bounds<F>(st: &mut PState, mut _conv: F) -> ty::BuiltinBounds w
 fn parse_builtin_bounds_<F>(st: &mut PState, _conv: &mut F) -> ty::BuiltinBounds where
     F: FnMut(DefIdSource, ast::DefId) -> ast::DefId,
 {
-    let mut builtin_bounds = ty::empty_builtin_bounds();
+    let mut builtin_bounds = ty::BuiltinBounds::empty();
 
     loop {
         match next(st) {