Teach the type-id/expression disambiguator about different

disambiguation contexts, so that we properly parse template arguments
such as

  A<int()>

as type-ids rather than as expressions. Since this can be confusing
(especially when the template parameter is a non-type template
parameter), we try to give a friendly error message.

Almost, eliminate a redundant error message (that should have been a
note) and add some ultra-basic checks for non-type template
arguments.

llvm-svn: 64189

2 files changed, 10 insertions, 9 deletions

diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.def b/clang/include/clang/Basic/DiagnosticSemaKinds.def
index d4d68a4d349..fd6055103b1 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.def
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.def
@@ -497,8 +497,6 @@ DIAG(note_template_nontype_parm_prev_declaration, NOTE,
 // C++ Template Argument Lists
 DIAG(err_template_arg_list_different_arity, ERROR,
      "%select{too few|too many}0 template arguments for %select{class template|function template|template template parameter|template}1 %2")
-DIAG(note_template_parameter_here, ERROR,
-     "template parameter is declared here")
 DIAG(err_template_arg_must_be_type, ERROR,
      "template argument for template type parameter must be a type")
 DIAG(err_template_arg_must_be_expr, ERROR,
diff --git a/clang/include/clang/Parse/Parser.h b/clang/include/clang/Parse/Parser.h
index 2d777ff7ba2..ab43c516cdb 100644
--- a/clang/include/clang/Parse/Parser.h
+++ b/clang/include/clang/Parse/Parser.h
@@ -819,12 +819,20 @@ private:
     return isDeclarationSpecifier();
   }
 
+  /// \brief Specifies the context in which type-id/expression
+  /// disambiguation will occur.
+  enum TentativeCXXTypeIdContext {
+    TypeIdInParens,
+    TypeIdAsTemplateArgument
+  };
+
+
   /// isTypeIdInParens - Assumes that a '(' was parsed and now we want to know
   /// whether the parens contain an expression or a type-id.
   /// Returns true for a type-id and false for an expression.
   bool isTypeIdInParens() {
     if (getLang().CPlusPlus)
-      return isCXXTypeIdInParens();
+      return isCXXTypeId(TypeIdInParens);
     return isTypeSpecifierQualifier();
   }
 
@@ -855,12 +863,7 @@ private:
   /// the function returns true to let the declaration parsing code handle it.
   bool isCXXConditionDeclaration();
 
-  /// isCXXTypeIdInParens - Assumes that a '(' was parsed and now we want to
-  /// know whether the parens contain an expression or a type-id.
-  /// Returns true for a type-id and false for an expression.
-  /// If during the disambiguation process a parsing error is encountered,
-  /// the function returns true to let the declaration parsing code handle it.
-  bool isCXXTypeIdInParens();
+  bool isCXXTypeId(TentativeCXXTypeIdContext Context);
 
   /// TPResult - Used as the result value for functions whose purpose is to
   /// disambiguate C++ constructs by "tentatively parsing" them.