[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

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@184763 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 38 insertions, 0 deletions

diff --git a/include/clang/AST/Type.h b/include/clang/AST/Type.h
index bd2e18878e..2566268a62 100644
--- a/include/clang/AST/Type.h
+++ b/include/clang/AST/Type.h
@@ -1991,6 +1991,44 @@ public:
   static bool classof(const Type *T) { return T->getTypeClass() == Pointer; }
 };
 
+/// \brief Represents a pointer type decayed from an array or function type.
+class DecayedType : public Type, public llvm::FoldingSetNode {
+  QualType OriginalType;
+  QualType DecayedPointer;
+
+  DecayedType(QualType OriginalType, QualType DecayedPointer,
+              QualType CanonicalPtr)
+      : Type(Decayed, CanonicalPtr, OriginalType->isDependentType(),
+             OriginalType->isInstantiationDependentType(),
+             OriginalType->isVariablyModifiedType(),
+             OriginalType->containsUnexpandedParameterPack()),
+        OriginalType(OriginalType), DecayedPointer(DecayedPointer) {
+    assert(isa<PointerType>(DecayedPointer));
+  }
+
+  friend class ASTContext;  // ASTContext creates these.
+
+public:
+  QualType getDecayedType() const { return DecayedPointer; }
+  QualType getOriginalType() const { return OriginalType; }
+
+  QualType getPointeeType() const {
+    return cast<PointerType>(DecayedPointer)->getPointeeType();
+  }
+
+  bool isSugared() const { return true; }
+  QualType desugar() const { return DecayedPointer; }
+
+  void Profile(llvm::FoldingSetNodeID &ID) {
+    Profile(ID, OriginalType);
+  }
+  static void Profile(llvm::FoldingSetNodeID &ID, QualType OriginalType) {
+    ID.AddPointer(OriginalType.getAsOpaquePtr());
+  }
+
+  static bool classof(const Type *T) { return T->getTypeClass() == Decayed; }
+};
+
 /// BlockPointerType - pointer to a block type.
 /// This type is to represent types syntactically represented as
 /// "void (^)(int)", etc. Pointee is required to always be a function type.