https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94602
Bug ID: 94602
Summary: wrong semantic check to prvalue as decltype operand
Product: gcc
Version: 9.3.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: frankhb1989 at gmail dot com
Target Milestone: ---
Case:
struct S
{
~S() = delete;
};
S f();
int main()
{
using X = decltype(f()); // #1
using Y = decltype(S{}); // #2
}
#2 is wrongly rejected in C++17 mode.
#1 is not ill-formed for the deleted destructor as per C++11
[dcl.type.simple]/5:
> ... in the case where the operand of a decltype-specifier
is a function call and the return type of the function is a class type, a
special rule (5.2.2) ensures that the return type is not required to be
complete (as it would be if the call appeared in a sub-expression or outside of
a
decltype-specifier) ... In particular, it is not necessary to allocate storage
for a temporary object or to enforce the semantic constraints associated with
invoking the type's destructor. ...
This rule is expanded by P0135R1 for cases like #2, which is adopted in C++17.
(See also P0929R2.)
