[ODRHash] Skip some typedef types.

In some cases, a typedef only strips aways a keyword for a type, keeping the
same name as the root record type.  This causes some confusion when the type
is defined in one modules but only forward declared in another.  Skipping the
typedef and going straight to the record will avoid this issue.

typedef struct S {} S;
S* s;  // S is TypedefType here

struct S;
S* s;  // S is RecordType here

llvm-svn: 364119

1 files changed, 45 insertions, 0 deletions

diff --git a/clang/lib/AST/ODRHash.cpp b/clang/lib/AST/ODRHash.cpp
index ba3b2ee49c5..e47154088d9 100644
--- a/clang/lib/AST/ODRHash.cpp
+++ b/clang/lib/AST/ODRHash.cpp
@@ -696,7 +696,52 @@ public:
     ID.AddInteger(Quals.getAsOpaqueValue());
   }
 
+  // Return the RecordType if the typedef only strips away a keyword.
+  // Otherwise, return the original type.
+  static const Type *RemoveTypedef(const Type *T) {
+    const auto *TypedefT = dyn_cast<TypedefType>(T);
+    if (!TypedefT) {
+      return T;
+    }
+
+    const TypedefNameDecl *D = TypedefT->getDecl();
+    QualType UnderlyingType = D->getUnderlyingType();
+
+    if (UnderlyingType.hasLocalQualifiers()) {
+      return T;
+    }
+
+    const auto *ElaboratedT = dyn_cast<ElaboratedType>(UnderlyingType);
+    if (!ElaboratedT) {
+      return T;
+    }
+
+    if (ElaboratedT->getQualifier() != nullptr) {
+      return T;
+    }
+
+    QualType NamedType = ElaboratedT->getNamedType();
+    if (NamedType.hasLocalQualifiers()) {
+      return T;
+    }
+
+    const auto *RecordT = dyn_cast<RecordType>(NamedType);
+    if (!RecordT) {
+      return T;
+    }
+
+    const IdentifierInfo *TypedefII = TypedefT->getDecl()->getIdentifier();
+    const IdentifierInfo *RecordII = RecordT->getDecl()->getIdentifier();
+    if (!TypedefII || !RecordII ||
+        TypedefII->getName() != RecordII->getName()) {
+      return T;
+    }
+
+    return RecordT;
+  }
+
   void Visit(const Type *T) {
+    T = RemoveTypedef(T);
     ID.AddInteger(T->getTypeClass());
     Inherited::Visit(T);
   }