2 files changed, 28 insertions, 0 deletions
diff --git a/lib/Sema/SemaTemplateInstantiate.cpp b/lib/Sema/SemaTemplateInstantiate.cpp
index 03c2befbc5..564f099ad9 100644
--- a/lib/Sema/SemaTemplateInstantiate.cpp
+++ b/lib/Sema/SemaTemplateInstantiate.cpp
@@ -1388,6 +1388,12 @@ static bool NeedsInstantiationAsFunctionType(TypeSourceInfo *T) {
   for (unsigned I = 0, E = FP.getNumArgs(); I != E; ++I) {
     ParmVarDecl *P = FP.getArg(I);
 
+    // The parameter's type as written might be dependent even if the
+    // decayed type was not dependent.
+    if (TypeSourceInfo *TSInfo = P->getTypeSourceInfo())
+      if (TSInfo->getType()->isDependentType())
+        return true;
+
     // TODO: currently we always rebuild expressions.  When we
     // properly get lazier about this, we should use the same
     // logic to avoid rebuilding prototypes here.
diff --git a/test/SemaTemplate/instantiate-function-1.cpp b/test/SemaTemplate/instantiate-function-1.cpp
index 688d009526..5406fbcd1b 100644
--- a/test/SemaTemplate/instantiate-function-1.cpp
+++ b/test/SemaTemplate/instantiate-function-1.cpp
@@ -225,3 +225,25 @@ namespace PR7016 {
   template<typename T> void f() { T x = x; }
   template void f<int>();
 }
+
+namespace PR9880 {
+  struct lua_State;
+  struct no_tag { char a; };			// (A)
+  struct yes_tag { long a; long b; };	// (A)
+
+  template <typename T>
+  struct HasIndexMetamethod {
+    template <typename U>
+    static no_tag check(...);
+    template <typename U>
+    static yes_tag check(char[sizeof(&U::luaIndex)]);
+    enum { value = sizeof(check<T>(0)) == sizeof(yes_tag) };
+  };
+  
+  class SomeClass {
+  public:
+    int luaIndex(lua_State* L);
+  };
+  
+  int i = HasIndexMetamethod<SomeClass>::value;
+}