Make newtype_index get debug_name using reflection

src/librustc_data_structures/indexed_vec.rs

@@ -40,6 +40,10 @@ impl Idx for u32 {
 
 #[macro_export]
 macro_rules! newtype_index {
+    ($name:ident) => (
+        newtype_index!($name, unsafe { ::std::intrinsics::type_name::<$name>() });
+    );
+
     ($name:ident, $debug_name:expr) => (
         #[derive(Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord,
          RustcEncodable, RustcDecodable)]

src/librustc_mir/lib.rs

@@ -18,6 +18,7 @@ Rust MIR: a lowered representation of Rust. Also: an experiment!
 
 #![feature(box_patterns)]
 #![feature(box_syntax)]
+#![feature(core_intrinsics)]
 #![feature(i128_type)]
 #![feature(rustc_diagnostic_macros)]
 #![feature(placement_in_syntax)]

src/librustc_mir/transform/nll/mod.rs

@@ -155,4 +155,4 @@ struct Region {
     points: FxHashSet<Location>,
 }
 
-newtype_index!(RegionIndex, "region_index");
+newtype_index!(RegionIndex);