[AST] Introduce a new DecayedType sugar node

The goal of this sugar node is to be able to look at an arbitrary
FunctionType and tell if any of the parameters were decayed from an
array or function type.  Ultimately this is necessary to implement
Microsoft's C++ name mangling scheme, which mangles decayed arrays
differently from normal pointers.

Reviewers: rsmith

Differential Revision: http://llvm-reviews.chandlerc.com/D1014

llvm-svn: 184763

1 files changed, 16 insertions, 0 deletions

diff --git a/clang/lib/Sema/TreeTransform.h b/clang/lib/Sema/TreeTransform.h
index 86624c580e5..9fbbe2cf1d5 100644
--- a/clang/lib/Sema/TreeTransform.h
+++ b/clang/lib/Sema/TreeTransform.h
@@ -3586,6 +3586,22 @@ QualType TreeTransform<Derived>::TransformComplexType(TypeLocBuilder &TLB,
 }
 
 template<typename Derived>
+QualType TreeTransform<Derived>::TransformDecayedType(TypeLocBuilder &TLB,
+                                                      DecayedTypeLoc TL) {
+  QualType OriginalType = getDerived().TransformType(TLB, TL.getOriginalLoc());
+  if (OriginalType.isNull())
+    return QualType();
+
+  QualType Result = TL.getType();
+  if (getDerived().AlwaysRebuild() ||
+      OriginalType != TL.getOriginalLoc().getType())
+    Result = SemaRef.Context.getDecayedType(OriginalType);
+  TLB.push<DecayedTypeLoc>(Result);
+  // Nothing to set for DecayedTypeLoc.
+  return Result;
+}
+
+template<typename Derived>
 QualType TreeTransform<Derived>::TransformPointerType(TypeLocBuilder &TLB,
                                                       PointerTypeLoc TL) {
   QualType PointeeType