[C++ PATCH] Add test for c++/67533 (or not?)

[Jason Merrill]

On 6/9/19 7:37 PM, Marek Polacek wrote:
> This testcase used to ICE but was fixed by r259067.  We now issue
> 
> 67533.C:5:26: error: conversion from ‘void’ to non-scalar type ‘Tls’ requested
>      5 | thread_local Tls mytls = mytls; // { dg-error "" }
>        |                          ^~~~~
> 
> whereas clang++ and icc compile it.  However, the test uses a reserved identifier
> ([lex.name]/3), and I think the error is fine.

> Do you think it's worth adding this test?  I thought so, just to check we don't
> ICE, but who uses a mangled name as an identifier?!

OK.

I suppose get_tls_wrapper_fn could check whether a previous declaration 
has the right type, to give a more helpful diagnostic.

The original testcase makes me wonder if we should be marking 
compiler-generated  functions as no_instrument_function.

Jason