c++: template-id arguments are evaluated [PR101906]

Here we're neglecting to clear cp_unevaluated_operand when substituting
into the arguments of the alias template-id 'skip<(T(), 0), T>' with T=A,
which means cp_unevaluated_operand remains set during mark_used for
A::A() and so we don't synthesize it.  Later constant evaluation for
the substituted template argument '(A(), 0)' (from coerce_template_parms)
fails with "'constexpr A::A()' used before its definition" since it was
never synthesized.

This doesn't happen with a class template because tsubst_aggr_type
clears cp_unevaluated_operand during substitution thereof.  But since
template arguments are generally manifestly constant-evaluated, which in
turn are evaluated even in an unevaluated operand, we should be clearing
cp_unevaluated_operand more broadly whenever substituting into any set
of template arguments.  To that end this patch makes us clear it during
tsubst_template_args.

	PR c++/101906

gcc/cp/ChangeLog:

	* pt.cc (tsubst_template_args): Set cp_evaluated here.
	(tsubst_aggr_type): Not here.

gcc/testsuite/ChangeLog:

	* g++.dg/template/evaluated1.C: New test.
	* g++.dg/template/evaluated1a.C: New test.
	* g++.dg/template/evaluated1b.C: New test.
	* g++.dg/template/evaluated1c.C: New test.

0 files changed, 0 insertions, 0 deletions