From c06280ac4c34b0aff8cfa2e74ae8c7afd759d52f Mon Sep 17 00:00:00 2001 From: Patrick Palka Date: Wed, 3 Jun 2020 16:37:24 -0400 Subject: [PATCH] c++: more constrained nested partial specialization When checking that a constrained partial specialization is more constrained than the primary template, we pass only the innermost level of generic template arguments to strictly_subsumes. This leads to us doing a nonsensical substitution from normalize_concept_check if the full set of template arguments has multiple levels, and it ultimately causes strictly_subsumes to sometimes erroneously return false as in the testcase below. gcc/cp/ChangeLog: * pt.c (process_partial_specialization): Pass the full set of generic template arguments to strictly_subsumes. gcc/testsuite/ChangeLog: * g++.dg/cpp2a/concepts-partial-spec8.C: New test. --- gcc/cp/pt.c | 2 +- .../g++.dg/cpp2a/concepts-partial-spec8.C | 14 ++++++++++++++ 2 files changed, 15 insertions(+), 1 deletion(-) create mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-partial-spec8.C diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c index f5d1442a400..c07a48f1261 100644 --- a/gcc/cp/pt.c +++ b/gcc/cp/pt.c @@ -5062,7 +5062,7 @@ process_partial_specialization (tree decl) if (comp_template_args (inner_args, INNERMOST_TEMPLATE_ARGS (main_args)) && (!flag_concepts || !strictly_subsumes (current_template_constraints (), - inner_args, maintmpl))) + main_args, maintmpl))) { if (!flag_concepts) error ("partial specialization %q+D does not specialize " diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-partial-spec8.C b/gcc/testsuite/g++.dg/cpp2a/concepts-partial-spec8.C new file mode 100644 index 00000000000..873cf44e407 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp2a/concepts-partial-spec8.C @@ -0,0 +1,14 @@ +// { dg-do compile { target c++20 } } + +template +concept equal = M == N; + +template +struct traits +{ + template requires equal + struct foo {}; + + template requires equal && (M >= 0) // { dg-bogus "not more constrained" } + struct foo {}; +}; -- 2.30.2