[gcc r13-5682] c++: excessive satisfaction in check_methods [PR108579]

[Patrick Palka <ppalka@gcc.gnu.org>]

https://gcc.gnu.org/g:e7930c6750d03b28d922ebbbace20ba9d8622c6a

commit r13-5682-ge7930c6750d03b28d922ebbbace20ba9d8622c6a
Author: Patrick Palka <ppalka@redhat.com>
Date:   Fri Feb 3 09:12:31 2023 -0500

    c++: excessive satisfaction in check_methods [PR108579]
    
    In check_methods we're unnecessarily checking satisfaction for all
    constructors and assignment operators, even those that don't look like
    copy/move special members.  In the testcase below this manifests as an
    unstable satisfaction error because the satisfaction result is first
    determined to be false during check_methods (since A<int> is incomplete
    at this point) and later true after completion of A<int>.
    
    This patch fixes this simply by swapping the order of the
    constraint_satisfied_p and copy/move_fn_p tests.
    
            PR c++/108579
    
    gcc/cp/ChangeLog:
    
            * class.cc (check_methods): Swap order of constraints_satisfied_p
            and copy/move_fn_p tests.
    
    gcc/testsuite/ChangeLog:
    
            * g++.dg/cpp2a/concepts-pr108579.C: New test.

Diff:
---
 gcc/cp/class.cc                                | 16 ++++++++--------
 gcc/testsuite/g++.dg/cpp2a/concepts-pr108579.C | 14 ++++++++++++++
 2 files changed, 22 insertions(+), 8 deletions(-)

diff --git a/gcc/cp/class.cc b/gcc/cp/class.cc
index a2aa6674590..40e6b7365a8 100644
--- a/gcc/cp/class.cc
+++ b/gcc/cp/class.cc
@@ -4822,11 +4822,11 @@ check_methods (tree t)
 	/* Might be trivial.  */;
       else if (TREE_CODE (fn) == TEMPLATE_DECL)
 	/* Templates are never special members.  */;
-      else if (!constraints_satisfied_p (fn))
-	/* Not eligible.  */;
-      else if (copy_fn_p (fn))
+      else if (copy_fn_p (fn)
+	       && constraints_satisfied_p (fn))
 	TYPE_HAS_COMPLEX_COPY_CTOR (t) = true;
-      else if (move_fn_p (fn))
+      else if (move_fn_p (fn)
+	       && constraints_satisfied_p (fn))
 	TYPE_HAS_COMPLEX_MOVE_CTOR (t) = true;
     }
 
@@ -4836,11 +4836,11 @@ check_methods (tree t)
 	/* Might be trivial.  */;
       else if (TREE_CODE (fn) == TEMPLATE_DECL)
 	/* Templates are never special members.  */;
-      else if (!constraints_satisfied_p (fn))
-	/* Not eligible.  */;
-      else if (copy_fn_p (fn))
+      else if (copy_fn_p (fn)
+	       && constraints_satisfied_p (fn))
 	TYPE_HAS_COMPLEX_COPY_ASSIGN (t) = true;
-      else if (move_fn_p (fn))
+      else if (move_fn_p (fn)
+	       && constraints_satisfied_p (fn))
 	TYPE_HAS_COMPLEX_MOVE_ASSIGN (t) = true;
     }
 }
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-pr108579.C b/gcc/testsuite/g++.dg/cpp2a/concepts-pr108579.C
new file mode 100644
index 00000000000..f8721f0ab86
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-pr108579.C
@@ -0,0 +1,14 @@
+// PR c++/108579
+// { dg-do compile { target c++20 } }
+
+template<class T>
+struct A {
+  A(double, char);
+  A(int) requires requires { A(0.0, 'c'); };
+  A& operator=(int) requires requires { A(1.0, 'd'); };
+};
+
+int main() {
+  A<int> a(3);
+  a = 5;
+}