From c52c190c1e790317e6448902fbf08511fb6c1789 Mon Sep 17 00:00:00 2001
From: Karthik Bhat <kv.bhat@samsung.com>
Date: Thu, 8 May 2014 13:16:20 +0000
Subject: [PATCH] Fix PR19169 [Crash on invalid attempting to specialize a
 template method as a template variable]. A template declaration of a template
 name can be null in case we have a dependent name or a set of function
 templates. Hence use dyn_cast_or_null instead of dyn_cast. Also improve the
 diagnostic emitted in this case.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@208313 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/clang/Basic/DiagnosticSemaKinds.td          |  3 +++
 lib/Sema/SemaTemplate.cpp                           | 13 +++++++++++--
 test/SemaCXX/cxx1y-variable-templates_top_level.cpp | 10 ++++++++++
 3 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/include/clang/Basic/DiagnosticSemaKinds.td b/include/clang/Basic/DiagnosticSemaKinds.td
index 27ca1c9346..e33d2c1666 100644
--- a/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/include/clang/Basic/DiagnosticSemaKinds.td
@@ -3314,6 +3314,9 @@ def note_var_prev_partial_spec_here : Note<
   "previous declaration of variable template partial specialization is here">;
 def err_var_spec_no_template : Error<
   "no variable template matches%select{| partial}0 specialization">;
+def err_var_spec_no_template_but_method : Error<
+  "no variable template matches specialization; "
+  "did you mean to use %0 as function template instead?">;
   
 // C++ Function template specializations
 def err_function_template_spec_no_match : Error<
diff --git a/lib/Sema/SemaTemplate.cpp b/lib/Sema/SemaTemplate.cpp
index e21d1eef46..8c0261381c 100644
--- a/lib/Sema/SemaTemplate.cpp
+++ b/lib/Sema/SemaTemplate.cpp
@@ -2420,10 +2420,19 @@ DeclResult Sema::ActOnVarTemplateSpecialization(
 
   // The template-id must name a variable template.
   VarTemplateDecl *VarTemplate =
-      dyn_cast<VarTemplateDecl>(Name.getAsTemplateDecl());
-  if (!VarTemplate)
+      dyn_cast_or_null<VarTemplateDecl>(Name.getAsTemplateDecl());
+  if (!VarTemplate) {
+    NamedDecl *FnTemplate;
+    if (auto *OTS = Name.getAsOverloadedTemplate())
+      FnTemplate = *OTS->begin();
+    else
+      FnTemplate = dyn_cast_or_null<FunctionTemplateDecl>(Name.getAsTemplateDecl());
+    if (FnTemplate)
+      return Diag(D.getIdentifierLoc(), diag::err_var_spec_no_template_but_method)
+               << FnTemplate->getDeclName();
     return Diag(D.getIdentifierLoc(), diag::err_var_spec_no_template)
              << IsPartialSpecialization;
+  }
 
   // Check for unexpanded parameter packs in any of the template arguments.
   for (unsigned I = 0, N = TemplateArgs.size(); I != N; ++I)
diff --git a/test/SemaCXX/cxx1y-variable-templates_top_level.cpp b/test/SemaCXX/cxx1y-variable-templates_top_level.cpp
index 37d5bf3a00..1ff64b334a 100644
--- a/test/SemaCXX/cxx1y-variable-templates_top_level.cpp
+++ b/test/SemaCXX/cxx1y-variable-templates_top_level.cpp
@@ -448,3 +448,13 @@ namespace PR19152 {
   static_assert(x<int> == 1, "");
 #endif
 }
+
+namespace PR19169 {
+  template <typename T> int* f();
+  template <typename T> void f();
+  template<> int f<double>; // expected-error {{no variable template matches specialization; did you mean to use 'f' as function template instead?}}
+  
+  template <typename T> void g();
+  template<> int g<double>; // expected-error {{no variable template matches specialization; did you mean to use 'g' as function template instead?}}
+}
+
-- 
2.40.0