Index: cfe/trunk/lib/Sema/SemaTemplate.cpp
===================================================================
--- cfe/trunk/lib/Sema/SemaTemplate.cpp
+++ cfe/trunk/lib/Sema/SemaTemplate.cpp
@@ -6403,11 +6403,11 @@
       // it will be a static member function until we know which template it
       // specializes), so adjust it now assuming it specializes this template.
       QualType FT = FD->getType();
+      const FunctionProtoType *FPT = FT->castAs<FunctionProtoType>();
+      FunctionDecl *TmplFD = FunTmpl->getTemplatedDecl();
       if (FD->isConstexpr()) {
-        CXXMethodDecl *OldMD =
-          dyn_cast<CXXMethodDecl>(FunTmpl->getTemplatedDecl());
+        CXXMethodDecl *OldMD = dyn_cast<CXXMethodDecl>(TmplFD);
         if (OldMD && OldMD->isConst()) {
-          const FunctionProtoType *FPT = FT->castAs<FunctionProtoType>();
           FunctionProtoType::ExtProtoInfo EPI = FPT->getExtProtoInfo();
           EPI.TypeQuals |= Qualifiers::Const;
           FT = Context.getFunctionType(FPT->getResultType(), FPT->getArgTypes(),
@@ -6415,6 +6415,16 @@
         }
       }
 
+      // Ignore differences in calling convention until decl merging.
+      const FunctionProtoType *TmplFT =
+          TmplFD->getType()->castAs<FunctionProtoType>();
+      if (FPT->getCallConv() != TmplFT->getCallConv()) {
+        FunctionProtoType::ExtProtoInfo EPI = FPT->getExtProtoInfo();
+        EPI.ExtInfo = EPI.ExtInfo.withCallingConv(TmplFT->getCallConv());
+        FT = Context.getFunctionType(FPT->getResultType(), FPT->getArgTypes(),
+                                     EPI);
+      }
+
       // C++ [temp.expl.spec]p11:
       //   A trailing template-argument can be left unspecified in the
       //   template-id naming an explicit function template specialization
Index: cfe/trunk/test/SemaCXX/decl-microsoft-call-conv.cpp
===================================================================
--- cfe/trunk/test/SemaCXX/decl-microsoft-call-conv.cpp
+++ cfe/trunk/test/SemaCXX/decl-microsoft-call-conv.cpp
@@ -144,3 +144,19 @@
 // expected-error@+2 {{stdcall and cdecl attributes are not compatible}}
 // expected-error@+1 {{fastcall and cdecl attributes are not compatible}}
 void __cdecl __cdecl __stdcall __cdecl __fastcall multi_cc(int x);
+
+template <typename T> void __stdcall StdcallTemplate(T) {}
+template <> void StdcallTemplate<int>(int) {}
+template <> void __stdcall StdcallTemplate<short>(short) {}
+
+// FIXME: Note the template, not the implicit instantiation.
+// expected-error@+2 {{function declared 'cdecl' here was previously declared 'stdcall}}
+// expected-note@+1 {{previous declaration is here}}
+template <> void __cdecl StdcallTemplate<long>(long) {}
+
+struct ExactlyInt {
+  template <typename T> static int cast_to_int(T) {
+    return T::this_is_not_an_int();
+  }
+};
+template <> inline int ExactlyInt::cast_to_int<int>(int x) { return x; }