3 files changed, 36 insertions, 5 deletions
diff --git a/clang/lib/AST/Decl.cpp b/clang/lib/AST/Decl.cpp
index 5b0404e38dd..2b22e5bb50a 100644
--- a/clang/lib/AST/Decl.cpp
+++ b/clang/lib/AST/Decl.cpp
@@ -4242,6 +4242,30 @@ TagDecl *TypedefNameDecl::getAnonDeclWithTypedefName(bool AnyRedecl) const {
   return nullptr;
 }
 
+bool TypedefNameDecl::isTransparentTagSlow() const {
+  auto determineIsTransparent = [&]() {
+    if (auto *TT = getUnderlyingType()->getAs<TagType>()) {
+      if (auto *TD = TT->getDecl()) {
+        if (TD->getName() != getName())
+          return false;
+        SourceLocation TTLoc = getLocation();
+        SourceLocation TDLoc = TD->getLocation();
+        if (!TTLoc.isMacroID() || !TDLoc.isMacroID())
+          return false;
+        SourceManager &SM = getASTContext().getSourceManager();
+        return SM.getSpellingLoc(TTLoc) == SM.getSpellingLoc(TDLoc);
+      }
+    }
+    return false;
+  };
+
+  bool isTransparent = determineIsTransparent();
+  CacheIsTransparentTag = 1;
+  if (isTransparent)
+    CacheIsTransparentTag |= 0x2;
+  return isTransparent;
+}
+
 TypedefDecl *TypedefDecl::CreateDeserialized(ASTContext &C, unsigned ID) {
   return new (C, ID) TypedefDecl(C, nullptr, SourceLocation(), SourceLocation(),
                                  nullptr, nullptr);
diff --git a/clang/lib/Index/IndexDecl.cpp b/clang/lib/Index/IndexDecl.cpp
index f9710236c9e..dae0cdc0d9c 100644
--- a/clang/lib/Index/IndexDecl.cpp
+++ b/clang/lib/Index/IndexDecl.cpp
@@ -231,8 +231,9 @@ public:
   }
 
   bool VisitTypedefNameDecl(const TypedefNameDecl *D) {
-    if (!IndexCtx.handleDecl(D))
-      return false;
+    if (!D->isTransparentTag())
+      if (!IndexCtx.handleDecl(D))
+        return false;
     IndexCtx.indexTypeSourceInfo(D->getTypeSourceInfo(), D);
     return true;
   }
diff --git a/clang/lib/Index/IndexTypeSourceInfo.cpp b/clang/lib/Index/IndexTypeSourceInfo.cpp
index 33848da0cb3..0645d5be526 100644
--- a/clang/lib/Index/IndexTypeSourceInfo.cpp
+++ b/clang/lib/Index/IndexTypeSourceInfo.cpp
@@ -47,9 +47,15 @@ public:
   } while (0)
 
   bool VisitTypedefTypeLoc(TypedefTypeLoc TL) {
+    SourceLocation Loc = TL.getNameLoc();
+    TypedefNameDecl *ND = TL.getTypedefNameDecl();
+    if (ND->isTransparentTag()) {
+      TagDecl *Underlying = ND->getUnderlyingType()->getAsTagDecl();
+      return IndexCtx.handleReference(Underlying, Loc, Parent,
+                                      ParentDC, SymbolRoleSet(), Relations);
+    }
     if (IsBase) {
-      SourceLocation Loc = TL.getNameLoc();
-      TRY_TO(IndexCtx.handleReference(TL.getTypedefNameDecl(), Loc,
+      TRY_TO(IndexCtx.handleReference(ND, Loc,
                                       Parent, ParentDC, SymbolRoleSet()));
       if (auto *CD = TL.getType()->getAsCXXRecordDecl()) {
         TRY_TO(IndexCtx.handleReference(CD, Loc, Parent, ParentDC,
@@ -57,7 +63,7 @@ public:
                                         Relations));
       }
     } else {
-      TRY_TO(IndexCtx.handleReference(TL.getTypedefNameDecl(), TL.getNameLoc(),
+      TRY_TO(IndexCtx.handleReference(ND, Loc,
                                       Parent, ParentDC, SymbolRoleSet(),
                                       Relations));
     }