C++ PATCH for c++/88548, this accepted in static member functions

[Jason Merrill]

On 12/22/18 4:38 PM, Marek Polacek wrote:
> I noticed that we weren't diagnosing using 'this' in noexcept-specifiers
> of static member functions, and Jakub pointed out that this is also true
> for trailing-return-type.  cp_parser has local_variables_forbidden_p to
> detect using local vars and 'this' in certain contexts, so let's use that.
> 
> ...except that I found out that I need to be able to distinguish between
> forbidding just local vars and/or this, so I've changed its type to char.
> For instance, you can't use 'this' in a static member function declaration,
> but you can use a local var because noexcept/decltype is an unevaluated
> context.
> 
> I also noticed that we weren't diagnosing 'this' in a friend declaration,
> which is also forbidden.
> 
> Bootstrapped/regtested on x86_64-linux, ok for trunk?

I wonder about suppressing inject_this_parm for a static member 
function, since current_class_ptr is unset within a static member 
function.  But this approach (and patch) is also OK.

Jason