[C++ Patch/RFC] PR 56450

[Paolo Carlini <paolo dot carlini at oracle dot com>]

Hi,

in this ICE on valid, finish_decltype_type doesn't handle a 
COMPOUND_EXPR when the second argument, 
id_expression_or_member_access_p, is true.

As analyzed by Jakub in the audit trail, at parsing time for the test 
involving:

   struct A3 { static const int dummy = 0; };

the *.dummy in the template argument of has_const_int_dummy is parsed as 
a COMPONENT_REF, but then, in case DECLTYPE_TYPE of tsubst it's turned 
into a COMPOUND_EXPR when it becomes clear that dummy is actually a 
static data member. Then id_expression_or_member_access_p == true, as 
stored in the DECLTYPE_TYPE, isn't correct anymore and 
finish_decltype_type can't handle its arguments.

Now, right before calling finish_decltype_type, we are *already* 
handling a case where, before the instantiation, we have ~id which, upon 
instantiation can turn out to be either a complement expression or a 
destructor: I thought we could handle in the same place this additional 
case of disambiguation and adjust id_expression_or_member_access_p to 
false in this case too. The below passes testing on x86_64-linux.

Thanks,
Paolo.

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