[Demangle][Rust] Parse references

Reviewed By: dblaikie

Part of https://reviews.llvm.org/D102580

llvm/lib/Demangle/RustDemangle.cpp

@@ -454,6 +454,16 @@ void Demangler::demangleType() {
     print(")");
     break;
   }
+  case 'R':
+    print("&");
+    // FIXME demangle [<lifetime>].
+    demangleType();
+    break;
+  case 'Q':
+    print("&mut ");
+    // FIXME demangle [<lifetime>].
+    demangleType();
+    break;
   case 'P':
     print("*const ");
     demangleType();

llvm/test/Demangle/rust.test

@@ -175,6 +175,12 @@ CHECK: types::<(_, _)>
 CHECK: types::<(_, _, _)>
        _RIC5typesTpppEE
 
+CHECK: types::<&_>
+       _RIC5typesRpE
+
+CHECK: types::<&mut _>
+       _RIC5typesQpE
+
 CHECK: types::<*const _>
        _RIC5typesPpE