Here we ICE on int f() requires (auto(0));
in do_auto_deduction when handling the auto: we're in a non-templated requires-expression which are parsed under processing_template_decl == 1 and empty current_template_parms, so 'current_template_args ()' will crash. This code is invalid as per "C++20 CA378: Remove non-templated constrained functions", but of course we shouldn't crash. Since in the scenario above it's expected that current_template_parms is null, I've just added a check, and let grokfndecl issue an error. I guess another approch would be to fake up a template parameter list before calling do_auto_deduction. For good measure, I've added several well-formed cases with auto(x) in a requires-expression. Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk? PR c++/103408 gcc/cp/ChangeLog: * pt.c (do_auto_deduction): Check current_template_parms before current_template_args (). gcc/testsuite/ChangeLog: * g++.dg/cpp23/auto-fncast9.C: New test. --- gcc/cp/pt.c | 2 +- gcc/testsuite/g++.dg/cpp23/auto-fncast9.C | 27 +++++++++++++++++++++++ 2 files changed, 28 insertions(+), 1 deletion(-) create mode 100644 gcc/testsuite/g++.dg/cpp23/auto-fncast9.C diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c index f4b9d9673fb..012ca5d06c0 100644 --- a/gcc/cp/pt.c +++ b/gcc/cp/pt.c @@ -30041,7 +30041,7 @@ do_auto_deduction (tree type, tree init, tree auto_node, (but we still may have used them for constraint checking above). */; else if (context == adc_unify) targs = add_to_template_args (outer_targs, targs); - else if (processing_template_decl) + else if (processing_template_decl && current_template_parms) targs = add_to_template_args (current_template_args (), targs); return tsubst (type, targs, complain, NULL_TREE); } diff --git a/gcc/testsuite/g++.dg/cpp23/auto-fncast9.C b/gcc/testsuite/g++.dg/cpp23/auto-fncast9.C new file mode 100644 index 00000000000..45a0ff9b460 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp23/auto-fncast9.C @@ -0,0 +1,27 @@ +// PR c++/103408 +// { dg-do compile { target c++23 } } + +int bad1() requires (auto(true)); // { dg-error "constraints on a non-templated function" } + +template<bool B> +int f1() requires (auto(B)); + +template<typename T> +struct S { T t; constexpr operator bool() { return true; } }; + +int bad2() requires (bool(S{1})); // { dg-error "constraints on a non-templated function" } +int bad3() requires (bool(S(1))); // { dg-error "constraints on a non-templated function" } + +template<int N> +int f2() requires (bool(S{N})); + +template<int N> +int f3() requires (bool(S(N))); + +void +g () +{ + f1<true>(); + f2<42>(); + f3<42>(); +} base-commit: 6b8ecbc6d6652d061d7c72c64352d51eca2df6ca -- 2.33.1