https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96444
Patrick Palka <ppalka at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Resolution|--- |FIXED
Status|ASSIGNED |RESOLVED
--- Comment #2 from Patrick Palka <ppalka at gcc dot gnu.org> ---
Note that the testcase in comment #0 can be simplified by making the constraint
not depend on T:
template<typename T, typename U> concept Same = __is_same(T, U);
template<typename T> void foo() { Same<bool> auto x = 0; }
void bar() { foo<bool>(); }
and yet we still accepted this invalid testcase. The reason for this is that
during do_auto_deduction at template parse time, since the initializer is
non-dependent we survived do_auto_deduction's early exit test and proceeded
with deduction. And since do_auto_deduction also ignores constraints when
processing_template_decl != 0, the overall deduction ended up succeeding and we
destructively resolved the placeholder variable type to 'int' at parse time
without ever checking the constraint.
Anyway, this is fixed for GCC 11 by r11-7454, which made do_auto_deduction give
up on deduction of a constrained placeholder type when
processing_template_decl, so that we can retry the deduction at instantiation
time instead.
