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* [gcc r14-8402] c++: ambiguous member lookup for rewritten cands [PR113529]
@ 2024-01-24 22:11 Patrick Palka
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From: Patrick Palka @ 2024-01-24 22:11 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:fecb45a936d62ca24dd8b4985ea0555c28edefa8
commit r14-8402-gfecb45a936d62ca24dd8b4985ea0555c28edefa8
Author: Patrick Palka <ppalka@redhat.com>
Date: Wed Jan 24 17:11:09 2024 -0500
c++: ambiguous member lookup for rewritten cands [PR113529]
Here we handle the operator expression u < v inconsistently: in a SFINAE
context we accept it, and in a non-SFINAE context we reject it with
error: request for member 'operator<=>' is ambiguous
as per [class.member.lookup]/6. This inconsistency is ultimately
because we neglect to propagate error_mark_node after recursing in
add_operator_candidates, fixed like so.
PR c++/113529
gcc/cp/ChangeLog:
* call.cc (add_operator_candidates): Propagate error_mark_node
result after recursing to find rewritten candidates.
gcc/testsuite/ChangeLog:
* g++.dg/cpp2a/spaceship-sfinae3.C: New test.
Reviewed-by: Jason Merrill <jason@redhat.com>
Diff:
---
gcc/cp/call.cc | 21 +++++++++++++++------
gcc/testsuite/g++.dg/cpp2a/spaceship-sfinae3.C | 22 ++++++++++++++++++++++
2 files changed, 37 insertions(+), 6 deletions(-)
diff --git a/gcc/cp/call.cc b/gcc/cp/call.cc
index 77f51bacce3..9de0d77c423 100644
--- a/gcc/cp/call.cc
+++ b/gcc/cp/call.cc
@@ -6828,7 +6828,9 @@ op_is_ordered (tree_code code)
/* Subroutine of build_new_op: Add to CANDIDATES all candidates for the
operator indicated by CODE/CODE2. This function calls itself recursively to
- handle C++20 rewritten comparison operator candidates.
+ handle C++20 rewritten comparison operator candidates. Returns NULL_TREE
+ upon success, and error_mark_node if something went wrong that prevented
+ us from performing overload resolution (e.g. ambiguous member name lookup).
LOOKUPS, if non-NULL, is the set of pertinent namespace-scope operator
overloads to consider. This parameter is used when instantiating a
@@ -7005,11 +7007,16 @@ add_operator_candidates (z_candidate **candidates,
if (rewrite_code)
{
+ tree r;
flags |= LOOKUP_REWRITTEN;
if (rewrite_code != code)
- /* Add rewritten candidates in same order. */
- add_operator_candidates (candidates, rewrite_code, ERROR_MARK,
- arglist, lookups, flags, complain);
+ {
+ /* Add rewritten candidates in same order. */
+ r = add_operator_candidates (candidates, rewrite_code, ERROR_MARK,
+ arglist, lookups, flags, complain);
+ if (r == error_mark_node)
+ return error_mark_node;
+ }
z_candidate *save_cand = *candidates;
@@ -7018,8 +7025,10 @@ add_operator_candidates (z_candidate **candidates,
vec<tree,va_gc> *revlist = make_tree_vector ();
revlist->quick_push ((*arglist)[1]);
revlist->quick_push ((*arglist)[0]);
- add_operator_candidates (candidates, rewrite_code, ERROR_MARK,
- revlist, lookups, flags, complain);
+ r = add_operator_candidates (candidates, rewrite_code, ERROR_MARK,
+ revlist, lookups, flags, complain);
+ if (r == error_mark_node)
+ return error_mark_node;
/* Release the vec if we didn't add a candidate that uses it. */
for (z_candidate *c = *candidates; c != save_cand; c = c->next)
diff --git a/gcc/testsuite/g++.dg/cpp2a/spaceship-sfinae3.C b/gcc/testsuite/g++.dg/cpp2a/spaceship-sfinae3.C
new file mode 100644
index 00000000000..ca159260ec7
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/spaceship-sfinae3.C
@@ -0,0 +1,22 @@
+// PR c++/113529
+// { dg-do compile { target c++20 } }
+
+#include <compare>
+
+struct A {
+ auto operator<=>(const A&) const = default;
+ bool operator<(const A&) const;
+};
+struct B {
+ auto operator<=>(const B&) const = default;
+};
+struct C : A, B { };
+
+
+template<class T>
+void f(T u, T v) {
+ static_assert(!requires { u < v; });
+ u < v; // { dg-error "request for member 'operator<=>' is ambiguous" }
+}
+
+template void f(C, C);
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