[Sema] Diagnose default argument on a parameter pack.

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

PR23028.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@233376 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/clang/Basic/DiagnosticSemaKinds.td b/include/clang/Basic/DiagnosticSemaKinds.td
index 388069f848d4746085346c637db7764260a620c9..9fa66db139167ad3e8869a9c9f4eafdc38a47c5f 100644 (file)
--- a/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/include/clang/Basic/DiagnosticSemaKinds.td
@@ -2808,6 +2808,8 @@ def err_param_default_argument_member_template_redecl : Error<
   "default arguments cannot be added to an out-of-line definition of a member "
   "of a %select{class template|class template partial specialization|nested "
   "class in a template}0">;
+def err_param_default_argument_on_parameter_pack : Error<
+  "parameter pack cannot have a default argument">;
 def err_uninitialized_member_for_assign : Error<
   "cannot define the implicit copy assignment operator for %0, because "
   "non-static %select{reference|const}1 member %2 can't use copy "

diff --git a/lib/Sema/SemaDeclCXX.cpp b/lib/Sema/SemaDeclCXX.cpp
index f7183bc2c4a6a5b77cdf6edfd42bc14d839e5a75..bb7ba943c60d47c4244a9ea9c3fd733b492b5a5c 100644 (file)
--- a/lib/Sema/SemaDeclCXX.cpp
+++ b/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)) {

diff --git a/test/CXX/dcl.decl/dcl.meaning/dcl.fct.default/p3.cpp b/test/CXX/dcl.decl/dcl.meaning/dcl.fct.default/p3.cpp
index e03c2164bae12c72f842e306a0e9a3ef64613711..11c17f32728a1484b118fc3c14d07ae622837b60 100644 (file)
--- a/test/CXX/dcl.decl/dcl.meaning/dcl.fct.default/p3.cpp
+++ b/test/CXX/dcl.decl/dcl.meaning/dcl.fct.default/p3.cpp
@@ -14,3 +14,6 @@ struct X0 {
   
   void mem8(int (*fp)(int) = (int (*)(int = 17))0); // expected-error{{default arguments can only be specified for parameters in a function declaration}}  
 };
+
+template <typename... Ts>
+void defaultpack(Ts... = 0) {} // expected-error{{parameter pack cannot have a default argument}}