gnu /
gcc /
9329344a6d81a6a5e3bd171167ebc7b158bb44f4 c++: concept-ids and value-dependence [PR102412]
The problem here is that uses_template_parms returns true for all
concept-ids (even those with non-dependent arguments), so when a concept-id
is used as a default template argument then during deduction the default
argument is considered dependent even after substituting into it, which
leads to deduction failure (from type_unification_real).
This patch fixes this by implementing the resolution of CWG 2446 which
says a concept-id is dependent only if its arguments are.
DR 2446
PR c++/102412
gcc/cp/ChangeLog:
* constexpr.c (cxx_eval_constant_expression)
<case TEMPLATE_ID_EXPR>: Check value_dependent_expression_p
instead of processing_template_decl.
* pt.c (value_dependent_expression_p) <case TEMPLATE_ID_EXPR>:
Return true only if any_dependent_template_arguments_p.
(instantiation_dependent_r) <case CALL_EXPR>: Remove this case.
<case TEMPLATE_ID_EXPR>: Likewise.
gcc/testsuite/ChangeLog:
* g++.dg/cpp2a/concepts-nondep2.C: New test.
* g++.dg/cpp2a/concepts-nondep3.C: New test.
4 files changed
