Re: [pushed] c++: module std and exception_ptr

[Jason Merrill <jason@redhat.com>]

On 6/13/24 11:16, Patrick Palka wrote:
> On Wed, 12 Jun 2024, Jason Merrill wrote:
> 
>> exception_ptr.h contains
>>
>>    namespace __exception_ptr
>>    {
>>      class exception_ptr;
>>    }
>>    using __exception_ptr::exception_ptr;
>>
>> so when module std tries to 'export using std::exception_ptr', it names
>> another using-directive rather than the class directly, so __exception_ptr
>> is never explicitly opened in module purview.
> 
> FWIW PR100134 ICEd in the same way, and r13-3236-g9736a42e1fb8df
> narrowly fixed this by setting DECL_MODULE_PURVIEW_P on the enclosing
> namespace around the time we set the flag on the namespace-scope entity in
> question.  I wonder if it'd be preferable to do something similar here,
> e.g. set DECL_MODULE_PURVIEW_P on the enclosing namespace in
> do_nonmember_using_decl?

Interesting thought, but I don't think so, as this is a workaround for 
the broader 114683 problem; we shouldn't actually be setting 
DECL_MODULE_PURVIEW_P on the class, either, only the using-declaration.
The problem is that we don't currently represent the using in a way that 
we can set flags on specifically.

Jason