Fixed error message when no type arguments are given (issue #1396)

[Theodus]

This PR resolves #1396 by passing the funref ast node to reify_defaults so that it may be used in error reporting in the case that no type arguments are given.

[jemc]

I would have taken a slightly different approach here.

That is, whenever an AST node is constructed, it is constructed from another one, meaning among other things that it will inherit the position information from the other one (the position information that is used to point to the error location if there is an error).

So in this case, somewhere in the code we are creating an empty TK_TYPEARGS node from the TK_TYPEPARAMS node if the TK_TYPEARGS node does not yet exist (because there are no type arguments). I would argue that we need to fix this bit of code to create the empty TK_TYPEARGS node from some other AST node instead (for example, the argument list AST node would probably be appropriate, so that the location caret (^) will point at the argument list parenthesis.

Let me know if you need any help tracking this down or figuring it out.

[Theodus]

@jemc Thanks for the different approach, it turns out that this is a much simpler fix.

[jemc]

Thanks!