Add support for WG21 N3599 (literal operator template for strings) as a GNU

extension. The GCC folks have decided to support this even though the standard
committee have not yet approved this feature.

Patch by Hristo Venev!

llvm-svn: 192128

1 files changed, 25 insertions, 3 deletions

diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
index 518f3156a9f..6d357e7be05 100644
--- a/clang/lib/Sema/SemaDeclCXX.cpp
+++ b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -10917,11 +10917,12 @@ bool Sema::CheckLiteralOperatorDeclaration(FunctionDecl *FnDecl) {
   if (!TpDecl)
     TpDecl = FnDecl->getPrimaryTemplate();
 
-  // template <char...> type operator "" name() is the only valid template
-  // signature, and the only valid signature with no parameters.
+  // template <char...> type operator "" name() and
+  // template <class T, T...> type operator "" name() are the only valid
+  // template signatures, and the only valid signatures with no parameters.
   if (TpDecl) {
     if (FnDecl->param_size() == 0) {
-      // Must have only one template parameter
+      // Must have one or two template parameters
       TemplateParameterList *Params = TpDecl->getTemplateParameters();
       if (Params->size() == 1) {
         NonTypeTemplateParmDecl *PmDecl =
@@ -10931,6 +10932,27 @@ bool Sema::CheckLiteralOperatorDeclaration(FunctionDecl *FnDecl) {
         if (PmDecl && PmDecl->isTemplateParameterPack() &&
             Context.hasSameType(PmDecl->getType(), Context.CharTy))
           Valid = true;
+      } else if (Params->size() == 2) {
+        TemplateTypeParmDecl *PmType =
+          dyn_cast<TemplateTypeParmDecl>(Params->getParam(0));
+        NonTypeTemplateParmDecl *PmArgs =
+          dyn_cast<NonTypeTemplateParmDecl>(Params->getParam(1));
+
+        // The second template parameter must be a parameter pack with the
+        // first template parameter as its type.
+        if (PmType && PmArgs &&
+            !PmType->isTemplateParameterPack() &&
+            PmArgs->isTemplateParameterPack()) {
+          const TemplateTypeParmType *TArgs =
+            PmArgs->getType()->getAs<TemplateTypeParmType>();
+          if (TArgs && TArgs->getDepth() == PmType->getDepth() &&
+              TArgs->getIndex() == PmType->getIndex()) {
+            Valid = true;
+            if (ActiveTemplateInstantiations.empty())
+              Diag(FnDecl->getLocation(),
+                   diag::ext_string_literal_operator_template);
+          }
+        }
       }
     }
   } else if (FnDecl->param_size()) {