Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look
OK for trunk and 15 after 15.2 is released?
-- >8 --
The below testcases started to get rejected due to overload resolution
ambiguity after r15-3740 which corrected our inheritedness tiebreaker to
only apply to constructors and not all member functions.
But arguably these testcases should be unambiguous because B::f
corresponds to and therefore hides A::f, so there should only be a
single candidate in the first place. We get this wrong because we try
comparing their constraints as written instead of the partially
substituted constraints as we do in other declaration matching contexts.
This patch fixes this by substituting in outer template arguments before
comparing constraints of two potentially corresponding member functions.
PR c++/121351
PR c++/119859
gcc/cp/ChangeLog:
* class.cc (add_method): Substitute in outer template arguments
into constraints before comparing them if the declarations are
from different classes.
gcc/testsuite/ChangeLog:
* g++.dg/cpp2a/concepts-using5.C: New test.
* g++.dg/cpp2a/concepts-using5a.C: New test.
---
gcc/cp/class.cc | 25 ++++++++++++++++++-
gcc/testsuite/g++.dg/cpp2a/concepts-using5.C | 19 ++++++++++++++
gcc/testsuite/g++.dg/cpp2a/concepts-using5a.C | 20 +++++++++++++++
3 files changed, 63 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-using5.C
create mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-using5a.C
diff --git a/gcc/cp/class.cc b/gcc/cp/class.cc
index f5d20e5c5392..14acb9c23c01 100644
--- a/gcc/cp/class.cc
+++ b/gcc/cp/class.cc
@@ -1356,7 +1356,30 @@ add_method (tree type, tree method, bool via_using)
if (!compparms (parms1, parms2))
continue;
- if (!equivalently_constrained (fn, method))
+ tree fn_constraints = get_constraints (fn);
+ tree method_constraints = get_constraints (method);
+
+ if (fn_constraints && method_constraints
+ && DECL_CONTEXT (fn) != type
+ && !processing_template_decl)
+ {
+ if (TREE_CODE (fn) == TEMPLATE_DECL)
+ ++processing_template_decl;
+ if (tree ti = CLASSTYPE_TEMPLATE_INFO (DECL_CONTEXT (fn)))
+ fn_constraints = tsubst_constraint_info (fn_constraints,
+ TI_ARGS (ti),
+ tf_warning_or_error,
+ fn);
+ if (tree ti = CLASSTYPE_TEMPLATE_INFO (DECL_CONTEXT (method)))
+ method_constraints = tsubst_constraint_info (method_constraints,
+ TI_ARGS (ti),
+ tf_warning_or_error,
+ method);
+ if (TREE_CODE (fn) == TEMPLATE_DECL)
+ --processing_template_decl;
+ }
+
+ if (!equivalent_constraints (fn_constraints, method_constraints))
{
if (processing_template_decl)
/* We can't check satisfaction in dependent context, wait until
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-using5.C
b/gcc/testsuite/g++.dg/cpp2a/concepts-using5.C
new file mode 100644
index 000000000000..d42b8a0167b9
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-using5.C
@@ -0,0 +1,19 @@
+// PR c++/121351
+// { dg-do compile { target c++20 } }
+
+template<class T> concept C = true;
+
+template<class T>
+struct A {
+ template<class U> void f(U) requires C<T> = delete; // #1
+};
+
+struct B : A<int> {
+ using A::f;
+ template<class U> void f(U) requires C<int>; // #2
+};
+
+int main() {
+ B b;
+ b.f(42); // OK, #2 corresponds to and therefore hides #1
+}
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-using5a.C
b/gcc/testsuite/g++.dg/cpp2a/concepts-using5a.C
new file mode 100644
index 000000000000..5d319481b480
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-using5a.C
@@ -0,0 +1,20 @@
+// PR c++/121351
+// { dg-do compile { target c++20 } }
+// A version of concepts-using5a.C where B instead of A is a template.
+
+template<class T> concept C = true;
+
+struct A {
+ template<class U> void f(U) requires C<int> = delete; // #1
+};
+
+template<class T>
+struct B : A {
+ using A::f;
+ template<class U> void f(U) requires C<T>; // #2
+};
+
+int main() {
+ B<int> b;
+ b.f(42); // OK, #2 corresponds to and therefore hides #1
+}
--
2.50.1.469.ge813a0200a
