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Re: Patch for constexpr variable templates

First of all, thanks a lot for taking this on!  A few nitpicks:

On 07/21/2014 11:06 PM, Braden Obrzut wrote:
 grokvardecl (tree type,
             tree name,
+                tree orig_declarator,
             const cp_decl_specifier_seq *declspecs,
             int initialized,
             int constp,
+                int template_count,

Indentation mismatch.

+  if (orig_declarator && (processing_template_decl
+      || TREE_CODE (orig_declarator) == TEMPLATE_ID_EXPR))

The indentation is wrong, since the || is part of the inner parenthesized expression.

+      /* Variable templates will need to have the class context.  */
+      if (VAR_P (value))
+        DECL_CONTEXT (value) = current_class_type;

Why isn't this covered by grokvardecl?

-  if (!is_overloaded_fn (fns))
+  bool var_templ = variable_template_p (fns);
+  if (!is_overloaded_fn (fns) && !var_templ)
       error ("%qD is not a function template", fns);

I think here we should check whether 'fns' and 'decl' are both variables or both functions so that we can give a better diagnostic.

+      if (cxx_dialect < cxx1y)
+        permerror (DECL_SOURCE_LOCATION (decl),
+                   "%qD is not a static data member of a class template", decl);

It's customary to use pedwarn and mention the relevant -std= flag.

+  if ((specialization || member_specialization)
+         /* Variable templates don't apply.  */
+         && (TREE_CODE (TREE_TYPE (decl)) == FUNCTION_TYPE
+             || TREE_CODE (TREE_TYPE (decl)) == METHOD_TYPE))

Indentation mismatch.

+      // Namespace scope variable templates should have a template header.


+         if (!variable_template_p (tmpl)
+                 && DECL_STATIC_FUNCTION_P (tmpl)
+         if (!variable_template_p (tmpl))
+           copy_default_args_to_explicit_spec (decl);

I'd prefer to check for a function template here rather than "not a variable template".

+      else if (VAR_P (decl))
+        {
+          if (!DECL_DECLARED_CONSTEXPR_P (decl))
+            error ("template declaration of non-constexpr variable %qD", decl);
+        }

As Ed and Andrew pointed out, non-constexpr variable templates are fine.

+  bool var_templ = DECL_TEMPLATE_INFO (decl)
+                   && variable_template_p (DECL_TI_TEMPLATE (decl));

An expression on multiple lines should be parenthesized to preserve indentation.

+         bool enter_context = CLASS_TYPE_P (DECL_CONTEXT (d));


+  return instantiate_template (TREE_OPERAND (var, 0), TREE_OPERAND (var, 1), tf_error);

Line too long.


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