On 2/14/22 11:32, Patrick Palka wrote:
Here the template context for the atomic constraint has two levels of template arguments, but since it depends only on the innermost argument T we use a single-level argument vector during substitution into the constraint (built by get_mapped_args). We eventually pass this vector to do_auto_deduction as part of checking the return-type-requirement inside the atom, but do_auto_deduction expects outer_targs to be a full set of arguments for sake of satisfaction.
Could we note the current number of levels in the map and use that in get_mapped_args instead of the highest level parameter we happened to use?
do_auto_deduction has a workaround in place to compensate for callers that pass only the innermost arguments as outer_targs, but here we're passing the _outermost_ arguments. Since the former situation should now (after r12-7101) only occur with adc_unify callers and the latter only with adc_requirement callers, this patch conditions the existing workaround according to the auto_deduction_context: if the context is adc_requirement, we add dummy innermost levels, otherwise we add dummy outermost levels as before and also assert that the context is adc_unify. Bootstrapped and regtested on x86_64-pc-linux-gnu and tested on cmcstl2 and range-v3, does this look OK for trunk? PR c++/104527 gcc/cp/ChangeLog: * pt.cc (do_auto_deduction): When template argument levels are missing from outer_targs, fill in the innermost rather than the outermost levels with dummy args if the context is adc_requirement, otherwise also assert that the context is adc_unify. gcc/testsuite/ChangeLog: * g++.dg/cpp2a/concepts-return-req4.C: New test. --- gcc/cp/pt.cc | 28 +++++++++++++------ .../g++.dg/cpp2a/concepts-return-req4.C | 24 ++++++++++++++++ 2 files changed, 44 insertions(+), 8 deletions(-) create mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-return-req4.C diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc index 1b18e2a7787..4ff2710b8ba 100644 --- a/gcc/cp/pt.cc +++ b/gcc/cp/pt.cc @@ -30215,20 +30215,32 @@ do_auto_deduction (tree type, tree init, tree auto_node,tree full_targs = add_to_template_args (outer_targs, targs); - /* HACK: Compensate for callers not always communicating all levels of- outer template arguments by filling in the outermost missing levels - with dummy levels before checking satisfaction. We'll still crash - if the constraint depends on a template argument belonging to one of - these missing levels, but this hack otherwise allows us to handle a - large subset of possible constraints (including all non-dependent - constraints). */ if (int missing_levels = (TEMPLATE_TYPE_ORIG_LEVEL (auto_node) - TMPL_ARGS_DEPTH (full_targs))) { tree dummy_levels = make_tree_vec (missing_levels); for (int i = 0; i < missing_levels; ++i) TREE_VEC_ELT (dummy_levels, i) = make_tree_vec (0); - full_targs = add_to_template_args (dummy_levels, full_targs); + if (context == adc_requirement) + /* We're checking a requires-expr's return-type-requirement that's + part of an atomic constraint that doesn't depend on any innermost + template arguments, so OUTER_TARGS (built by get_mapped_args) is + missing at least one innermost level. Fill in the innermost + levels of OUTER_TARGS with dummy levels. */ + full_targs = add_to_template_args + (add_to_template_args (outer_targs, dummy_levels), targs); + else + { + /* Otherwise, fill in the _outermost_ levels with dummy levels. + This compensates for adc_unify callers that only pass the + innermost level of template arguments as OUTER_TARGS. We'll + still crash if the constraint depends on a template argument + belonging to one of these missing levels, but this hack + otherwise allows us to handle a large subset of possible + constraints (including all non-dependent constraints). */ + gcc_checking_assert (context == adc_unify); + full_targs = add_to_template_args (dummy_levels, full_targs); + } }if (!constraints_satisfied_p (auto_node, full_targs))diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-return-req4.C b/gcc/testsuite/g++.dg/cpp2a/concepts-return-req4.C new file mode 100644 index 00000000000..471946bc8eb --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp2a/concepts-return-req4.C @@ -0,0 +1,24 @@ +// PR c++/104527 +// { dg-do compile { target c++20 } } + +template<class T, class U> +concept is_same = __is_same(T, U); + +template<class T> +struct A { + template<class...> + requires requires { { 0 } -> is_same<T>; } + struct B {}; + + template<class...> + requires requires { { 1 } -> is_same<T>; } + static void f(); +}; + +A<int>::B<> a1; +A<bool>::B<> a2; // { dg-error "constraint" } + +int main() { + A<int>::f(); + A<bool>::f(); // { dg-error "no match" } +}
