Keep track of more information within the template instantiation stack, e.g.,

by distinguishing between substitution that occurs for template
argument deduction vs. explicitly-specifiad template arguments. This
is used both to improve diagnostics and to make sure we only provide
SFINAE in those cases where SFINAE should apply.

In addition, deal with the sticky issue where SFINAE only considers
substitution of template arguments into the *type* of a function
template; we need to issue hard errors beyond this point, as
test/SemaTemplate/operator-template.cpp illustrates.

llvm-svn: 74651

1 files changed, 22 insertions, 9 deletions

diff --git a/clang/lib/Sema/Sema.h b/clang/lib/Sema/Sema.h
index 338221e4d41..a6c34e88857 100644
--- a/clang/lib/Sema/Sema.h
+++ b/clang/lib/Sema/Sema.h
@@ -2359,7 +2359,7 @@ public:
   /// \brief A template instantiation that is currently in progress.
   struct ActiveTemplateInstantiation {
     /// \brief The kind of template instantiation we are performing
-    enum {
+    enum InstantiationKind {
       /// We are instantiating a template declaration. The entity is
       /// the declaration we're instantiating (e.g., a CXXRecordDecl).
       TemplateInstantiation,
@@ -2371,13 +2371,16 @@ public:
       /// FIXME: Use a TemplateArgumentList
       DefaultTemplateArgumentInstantiation,
 
-      /// We are performing template argument deduction for a class
-      /// template partial specialization. The Entity is the class
-      /// template partial specialization, and
-      /// TemplateArgs/NumTemplateArgs provides the deduced template
-      /// arguments.
-      /// FIXME: Use a TemplateArgumentList
-      PartialSpecDeductionInstantiation
+      /// We are substituting explicit template arguments provided for 
+      /// a function template. The entity is a FunctionTemplateDecl.
+      ExplicitTemplateArgumentSubstitution,
+      
+      /// We are substituting template argument determined as part of
+      /// template argument deduction for either a class template
+      /// partial specialization or a function template. The
+      /// Entity is either a ClassTemplatePartialSpecializationDecl or
+      /// a FunctionTemplateDecl.
+      DeducedTemplateArgumentSubstitution
     } Kind;
 
     /// \brief The point of instantiation within the source code.
@@ -2411,7 +2414,8 @@ public:
         return true;
 
       case DefaultTemplateArgumentInstantiation:
-      case PartialSpecDeductionInstantiation:
+      case ExplicitTemplateArgumentSubstitution:
+      case DeducedTemplateArgumentSubstitution:
         return X.TemplateArgs == Y.TemplateArgs;
       }
 
@@ -2468,6 +2472,15 @@ public:
                           unsigned NumTemplateArgs,
                           SourceRange InstantiationRange = SourceRange());
 
+    /// \brief Note that we are instantiating a default argument in a
+    /// template-id.
+    InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
+                          FunctionTemplateDecl *FunctionTemplate,
+                          const TemplateArgument *TemplateArgs,
+                          unsigned NumTemplateArgs,
+                          ActiveTemplateInstantiation::InstantiationKind Kind,
+                          SourceRange InstantiationRange = SourceRange());
+    
     /// \brief Note that we are instantiating as part of template
     /// argument deduction for a class template partial
     /// specialization.