From 1b029d302fa469975b82779303660c3ed35cc9b7 Mon Sep 17 00:00:00 2001
From: Nick Lewycky <nicholas@mxc.ca>
Date: Mon, 10 Aug 2015 21:54:08 +0000
Subject: [PATCH] If a variable template is inside a context with template
 arguments that is being instantiated, and that instantiation fails, fail our
 instantiation instead of crashing. Errors have already been emitted.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@244515 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Sema/SemaTemplateInstantiateDecl.cpp           |  1 +
 test/SemaCXX/cxx1y-variable-templates_in_class.cpp | 11 +++++++++++
 2 files changed, 12 insertions(+)

diff --git a/lib/Sema/SemaTemplateInstantiateDecl.cpp b/lib/Sema/SemaTemplateInstantiateDecl.cpp
index 4fa54257ee..c8a067658b 100644
--- a/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -1143,6 +1143,7 @@ Decl *TemplateDeclInstantiator::VisitVarTemplateDecl(VarTemplateDecl *D) {
   VarDecl *VarInst =
       cast_or_null<VarDecl>(VisitVarDecl(Pattern,
                                          /*InstantiatingVarTemplate=*/true));
+  if (!VarInst) return nullptr;
 
   DeclContext *DC = Owner;
 
diff --git a/test/SemaCXX/cxx1y-variable-templates_in_class.cpp b/test/SemaCXX/cxx1y-variable-templates_in_class.cpp
index 123fcfff7f..65e2d6b608 100644
--- a/test/SemaCXX/cxx1y-variable-templates_in_class.cpp
+++ b/test/SemaCXX/cxx1y-variable-templates_in_class.cpp
@@ -327,3 +327,14 @@ struct S {
   static int f : I; // expected-error {{static member 'f' cannot be a bit-field}}
 };
 }
+
+namespace b20896909 {
+  // This used to crash.
+  template<typename T> struct helper {};
+  template<typename T> class A {
+    template <typename> static helper<typename T::error> x;  // expected-error {{type 'int' cannot be used prior to '::' because it has no members}}
+  };
+  void test() {
+    A<int> ai;  // expected-note {{in instantiation of}}
+  }
+}
-- 
2.40.0