https://gcc.gnu.org/g:2861eb34e30973cb991a7964af7cfeae014a98b0
commit r15-2230-g2861eb34e30973cb991a7964af7cfeae014a98b0
Author: Patrick Palka <ppa...@redhat.com>
Date: Tue Jul 23 13:16:14 2024 -0400
c++: normalizing ttp constraints [PR115656]
Here we normalize the constraint same_as<T, bool> for the first
time during ttp coercion of B / UU, specifically constraint subsumption
checking. During this normalization the set of in-scope template
parameters i.e. current_template_parms is empty, which we rely on
during normalization of the ttp constraints since we pass in_decl=NULL_TREE
to norm_info. And this tricks the satisfaction cache into thinking that
the satisfaction value of same_as<T, bool> is independent of its template
parameters, and we incorrectly conflate the satisfaction value with
T = bool vs T = long and accept the specialization A<long, B>.
Since is_compatible_template_arg rewrites the ttp's constraints to
be in terms of the argument template's parameters, and since it's
the only caller of weakly_subsumes, the latter funcion can instead
pass in_decl=tmpl to avoid relying on current_template_parms. This
patch implements this, and in turns renames weakly_subsumes to
ttp_subsumes to reflect that this predicate is now hardcoded for this
one caller.
PR c++/115656
gcc/cp/ChangeLog:
* constraint.cc (weakly_subsumes): Pass in_decl=tmpl to
get_normalized_constraints_from_info. Rename to ...
(ttp_subsumes): ... this.
* cp-tree.h (weakly_subsumes): Rename to ...
(ttp_subsumes): ... this.
* pt.cc (is_compatible_template_arg): Adjust after renaming.
gcc/testsuite/ChangeLog:
* g++.dg/cpp2a/concepts-ttp7.C: New test.
Reviewed-by: Jason Merrill <ja...@redhat.com>
Diff:
---
gcc/cp/constraint.cc | 9 +++++----
gcc/cp/cp-tree.h | 2 +-
gcc/cp/pt.cc | 2 +-
gcc/testsuite/g++.dg/cpp2a/concepts-ttp7.C | 12 ++++++++++++
4 files changed, 19 insertions(+), 6 deletions(-)
diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc
index afd5435cc3ed..7fce78f508e9 100644
--- a/gcc/cp/constraint.cc
+++ b/gcc/cp/constraint.cc
@@ -3328,13 +3328,14 @@ strictly_subsumes (tree ci, tree tmpl)
return subsumes (n1, n2) && !subsumes (n2, n1);
}
-/* Returns true when the constraints in CI subsume the
- associated constraints of TMPL. */
+/* Returns true when the template template parameter constraints in CI
+ subsume the associated constraints of the template template argument
+ TMPL. */
bool
-weakly_subsumes (tree ci, tree tmpl)
+ttp_subsumes (tree ci, tree tmpl)
{
- tree n1 = get_normalized_constraints_from_info (ci, NULL_TREE);
+ tree n1 = get_normalized_constraints_from_info (ci, tmpl);
tree n2 = get_normalized_constraints_from_decl (tmpl);
return subsumes (n1, n2);
diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index 76ac9c31763c..856699de82f2 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -8609,7 +8609,7 @@ extern tree find_template_parameters (tree,
tree);
extern bool equivalent_constraints (tree, tree);
extern bool equivalently_constrained (tree, tree);
extern bool strictly_subsumes (tree, tree);
-extern bool weakly_subsumes (tree, tree);
+extern bool ttp_subsumes (tree, tree);
extern int more_constrained (tree, tree);
extern bool at_least_as_constrained (tree, tree);
extern bool constraints_equivalent_p (tree, tree);
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 8cc5e21c520d..393913294b50 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -8482,7 +8482,7 @@ is_compatible_template_arg (tree parm, tree arg, tree
args)
return false;
}
- return weakly_subsumes (parm_cons, arg);
+ return ttp_subsumes (parm_cons, arg);
}
// Convert a placeholder argument into a binding to the original
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-ttp7.C
b/gcc/testsuite/g++.dg/cpp2a/concepts-ttp7.C
new file mode 100644
index 000000000000..2ce884b995c7
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-ttp7.C
@@ -0,0 +1,12 @@
+// PR c++/115656
+// { dg-do compile { target c++20 } }
+
+template<class T, class U> concept same_as = __is_same(T, U);
+
+template<same_as<bool> T, template<same_as<bool>> class UU>
+struct A { };
+
+template<same_as<bool>> class B;
+
+A<bool, B> a1;
+A<long, B> a2; // { dg-error "constraint failure" }
