> It seems that the problem here is more general; a template argument list is > not in scope within that same template argument list. Can't we fix that > without special-casing conversion ops?
I think conversion ops really are a special case. It's the only case where the template parameters refer to the template argument list from the cast operator's enclosing template. In a cast expression, like anywhere else you might have a template parameter, the template parameter refers to the template argument list of the immediately enclosing template. I think this note from Section 5.1.3 (Operator Encodings) of the ABI is what makes this a special case (it's an informative comment in the document, but seems to me to be normative): "For a user-defined conversion operator the result type (i.e., the type to which the operator converts) is part of the mangled name of the function. If the conversion operator is a member template, the result type will appear before the template parameters. There may be forward references in the result type to the template parameters." -cary
