[Sema] Diagnose default argument on a parameter pack.

This is ill-formed (and cannot be used anyways).

PR23028.

llvm-svn: 233376

1 files changed, 11 insertions, 2 deletions

diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
index f7183bc2c4a..bb7ba943c60 100644
--- a/clang/lib/Sema/SemaDeclCXX.cpp
+++ b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -316,8 +316,17 @@ Sema::ActOnParamDefaultArgument(Decl *param, SourceLocation EqualLoc,
   if (DiagnoseUnexpandedParameterPack(DefaultArg, UPPC_DefaultArgument)) {
     Param->setInvalidDecl();
     return;
-  }    
-      
+  }
+
+  // C++11 [dcl.fct.default]p3
+  //   A default argument expression [...] shall not be specified for a
+  //   parameter pack.
+  if (Param->isParameterPack()) {
+    Diag(EqualLoc, diag::err_param_default_argument_on_parameter_pack)
+        << DefaultArg->getSourceRange();
+    return;
+  }
+
   // Check that the default argument is well-formed
   CheckDefaultArgumentVisitor DefaultArgChecker(DefaultArg, this);
   if (DefaultArgChecker.Visit(DefaultArg)) {