From e9fc8dc84c4da2e9aea44c6e1a7bcc2af99d91c2 Mon Sep 17 00:00:00 2001
From: Douglas Gregor <dgregor@apple.com>
Date: Tue, 21 Dec 2010 21:22:51 +0000
Subject: [PATCH] When searching for the instantiation of a locally-scoped tag
 declaration, also look for an instantiation of its previous declarations.
 Fixes PR8801.

llvm-svn: 122361
---
 clang/lib/Sema/SemaTemplateInstantiate.cpp    | 20 ++++++++++++++-----
 .../SemaTemplate/instantiate-local-class.cpp  | 13 ++++++++++++
 2 files changed, 28 insertions(+), 5 deletions(-)

diff --git a/clang/lib/Sema/SemaTemplateInstantiate.cpp b/clang/lib/Sema/SemaTemplateInstantiate.cpp
index 37d8d8cb53de..2fa4ac5b0b24 100644
--- a/clang/lib/Sema/SemaTemplateInstantiate.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiate.cpp
@@ -1735,11 +1735,21 @@ Decl *LocalInstantiationScope::getInstantiationOf(const Decl *D) {
   for (LocalInstantiationScope *Current = this; Current; 
        Current = Current->Outer) {
     // Check if we found something within this scope.
-    llvm::DenseMap<const Decl *, Decl *>::iterator Found
-      = Current->LocalDecls.find(D);
-    if (Found != Current->LocalDecls.end())
-      return Found->second;
-   
+    const Decl *CheckD = D;
+    do {
+      llvm::DenseMap<const Decl *, Decl *>::iterator Found
+        = Current->LocalDecls.find(CheckD);
+      if (Found != Current->LocalDecls.end())
+        return Found->second;
+      
+      // If this is a tag declaration, it's possible that we need to look for
+      // a previous declaration.
+      if (const TagDecl *Tag = dyn_cast<TagDecl>(CheckD))
+        CheckD = Tag->getPreviousDeclaration();
+      else
+        CheckD = 0;
+    } while (CheckD);
+    
     // If we aren't combined with our outer scope, we're done. 
     if (!Current->CombineWithOuterScope)
       break;
diff --git a/clang/test/SemaTemplate/instantiate-local-class.cpp b/clang/test/SemaTemplate/instantiate-local-class.cpp
index d57ba8a68288..954fd6508589 100644
--- a/clang/test/SemaTemplate/instantiate-local-class.cpp
+++ b/clang/test/SemaTemplate/instantiate-local-class.cpp
@@ -50,3 +50,16 @@ namespace local_class_with_virtual_functions {
   struct S { };
   void test() { f<S>(); }
 }
+
+namespace PR8801 {
+  template<typename T>
+  void foo() {
+    class X;
+    int (X::*pmf)(T) = 0;
+    class X : public T { };
+  }
+
+  struct Y { };
+
+  template void foo<Y>();
+}