From 1f5a30d156f6323ba6f4ee3e0542f42e75687ddf Mon Sep 17 00:00:00 2001
From: Manman Ren <manman.ren@gmail.com>
Date: Wed, 24 Feb 2016 23:05:43 +0000
Subject: [PATCH] Fix assertion failure on MaybeODRUseExprs.

In VisitNonTypeTemplateParamDecl, before SubstExpr with the default argument,
we should create a ConstantEvaluated ExpressionEvaluationContext. Without this,
it is possible to use a PotentiallyEvaluated ExpressionEvaluationContext; and
MaybeODRUseExprs will not be cleared when popping the context, causing
assertion failure.

This is similar to how we handle the context before SubstExpr with the
default argument, in SubstDefaultTemplateArgument.

Part of PR13986.
rdar://24480205

Differential Revision: http://reviews.llvm.org/D17576


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@261803 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Sema/SemaTemplateInstantiateDecl.cpp      |  2 ++
 test/SemaTemplate/default-arguments-cxx0x.cpp | 10 ++++++++++
 2 files changed, 12 insertions(+)

diff --git a/lib/Sema/SemaTemplateInstantiateDecl.cpp b/lib/Sema/SemaTemplateInstantiateDecl.cpp
index a76550024b..829d51ee96 100644
--- a/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -2110,6 +2110,8 @@ Decl *TemplateDeclInstantiator::VisitNonTypeTemplateParmDecl(
     Param->setInvalidDecl();
 
   if (D->hasDefaultArgument() && !D->defaultArgumentWasInherited()) {
+    EnterExpressionEvaluationContext ConstantEvaluated(SemaRef,
+                                                       Sema::ConstantEvaluated);
     ExprResult Value = SemaRef.SubstExpr(D->getDefaultArgument(), TemplateArgs);
     if (!Value.isInvalid())
       Param->setDefaultArgument(Value.get());
diff --git a/test/SemaTemplate/default-arguments-cxx0x.cpp b/test/SemaTemplate/default-arguments-cxx0x.cpp
index 0c97c2056b..c52899a8e6 100644
--- a/test/SemaTemplate/default-arguments-cxx0x.cpp
+++ b/test/SemaTemplate/default-arguments-cxx0x.cpp
@@ -75,3 +75,13 @@ namespace rdar23810407 {
     g<int>();
   }
 }
+
+// rdar://problem/24480205
+namespace PR13986 {
+  constexpr unsigned Dynamic = 0;
+  template <unsigned> class A { template <unsigned = Dynamic> void m_fn1(); };
+  class Test {
+    ~Test() {}
+    A<1> m_target;
+  };
+}
-- 
2.50.1