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.
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" }
+}
--
2.35.1.102.g2b9c120970
