From 03bf10dc4f245a17ee4f702461cba5120cc4d09b Mon Sep 17 00:00:00 2001
From: Richard Trieu <rtrieu@google.com>
Date: Sat, 20 Jul 2013 03:49:02 +0000
Subject: [PATCH] If a default argument is a dependent type, get the real type
 from the desugared template.  Passing around dependent types can lead to
 integral arguments that cannot be evaluated.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@186757 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/AST/ASTDiagnostic.cpp           | 10 +++++++---
 test/Misc/diag-template-diffing.cpp | 26 ++++++++++++++++++++++++--
 2 files changed, 31 insertions(+), 5 deletions(-)

diff --git a/lib/AST/ASTDiagnostic.cpp b/lib/AST/ASTDiagnostic.cpp
index bc707ddbc1..eb22632c93 100644
--- a/lib/AST/ASTDiagnostic.cpp
+++ b/lib/AST/ASTDiagnostic.cpp
@@ -1054,10 +1054,14 @@ class TemplateDiff {
 
     if (!Iter.isEnd())
       return Iter->getAsType();
-    if (!isVariadic)
-      return DefaultTTPD->getDefaultArgument();
+    if (isVariadic)
+      return QualType();
+
+    QualType ArgType = DefaultTTPD->getDefaultArgument();
+    if (ArgType->isDependentType())
+      return Iter.getDesugar().getAsType();
 
-    return QualType();
+    return ArgType;
   }
 
   /// GetExpr - Retrieves the template expression argument, including default
diff --git a/test/Misc/diag-template-diffing.cpp b/test/Misc/diag-template-diffing.cpp
index cacc5c97fd..722ce98ecf 100644
--- a/test/Misc/diag-template-diffing.cpp
+++ b/test/Misc/diag-template-diffing.cpp
@@ -935,10 +935,10 @@ namespace DependentDefault {
     B<int, char> b3;
     b1 = b2;
     // CHECK-ELIDE-NOTREE: no viable overloaded '='
-    // CHECK-ELIDE-NOTREE: no known conversion from 'B<char, (default) Trait<T>::Ty>' to 'B<int, int>'
+    // CHECK-ELIDE-NOTREE: no known conversion from 'B<char, [...]>' to 'B<int, [...]>'
     b3 = b1;
     // CHECK-ELIDE-NOTREE: no viable overloaded '='
-    // CHECK-ELIDE-NOTREE: no known conversion from 'B<[...], (default) Trait<T>::Ty>' to 'B<[...], char>'
+    // CHECK-ELIDE-NOTREE: no known conversion from 'B<[...], (default) int>' to 'B<[...], char>'
     b2 = b3;
     // CHECK-ELIDE-NOTREE: no viable overloaded '='
     // CHECK-ELIDE-NOTREE: no known conversion from 'B<int, char>' to 'B<char, int>'
@@ -1029,6 +1029,28 @@ namespace PointerArguments {
   }
 }
 
+namespace DependentInt {
+  template<int Num> struct INT;
+
+  template <class CLASS, class Int_wrapper = INT<CLASS::val> >
+  struct C;
+
+  struct N {
+    static const int val = 1;
+  };
+
+  template <class M_T>
+  struct M {};
+
+  void test() {
+    using T1 = M<C<int, INT<0>>>;
+    using T2 = M<C<N>>;
+    T2 p;
+    T1 x = p;
+    // CHECK-ELIDE-NOTREE: no viable conversion from 'M<C<struct DependentInt::N, INT<1>>>' to 'M<C<int, INT<0>>>'
+  }
+}
+
 // CHECK-ELIDE-NOTREE: {{[0-9]*}} errors generated.
 // CHECK-NOELIDE-NOTREE: {{[0-9]*}} errors generated.
 // CHECK-ELIDE-TREE: {{[0-9]*}} errors generated.
-- 
2.40.0