The resolution of comment CA104 clarifies that we need to do direct
substitution of constraints in order to determine which member template
corresponds to an explicit specialization.
Tested x86_64-pc-linux-gnu, applying to trunk.
gcc/cp/ChangeLog
2020-05-11 Jason Merrill <ja...@redhat.com>
Resolve C++20 NB comment CA104
* pt.c (determine_specialization): Compare constraints for
specialization of member template of class instantiation.
---
gcc/cp/pt.c | 28 ++++++++++++++++++---
gcc/testsuite/g++.dg/cpp2a/concepts-spec1.C | 10 ++++++++
gcc/testsuite/g++.dg/template/nontype18.C | 2 +-
3 files changed, 36 insertions(+), 4 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-spec1.C
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 86f1bb7470d..84864561c25 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -2282,8 +2282,29 @@ determine_specialization (tree template_id,
below. */
if (tsk == tsk_template)
{
- if (compparms (fn_arg_types, decl_arg_types))
- candidates = tree_cons (NULL_TREE, fn, candidates);
+ if (!comp_template_parms (DECL_TEMPLATE_PARMS (fn),
+ current_template_parms))
+ continue;
+ if (!same_type_p (TREE_TYPE (TREE_TYPE (decl)),
+ TREE_TYPE (TREE_TYPE (fn))))
+ continue;
+ if (!compparms (fn_arg_types, decl_arg_types))
+ continue;
+
+ tree freq = get_trailing_function_requirements (fn);
+ tree dreq = get_trailing_function_requirements (decl);
+ if (!freq != !dreq)
+ continue;
+ if (freq)
+ {
+ tree fargs = DECL_TI_ARGS (fn);
+ tsubst_flags_t complain = tf_none;
+ freq = tsubst_constraint (freq, fargs, complain, fn);
+ if (!cp_tree_equal (freq, dreq))
+ continue;
+ }
+
+ candidates = tree_cons (NULL_TREE, fn, candidates);
continue;
}
@@ -2472,7 +2493,8 @@ determine_specialization (tree template_id,
*targs_out = copy_node (DECL_TI_ARGS (fn));
/* Propagate the candidate's constraints to the declaration. */
- set_constraints (decl, get_constraints (fn));
+ if (tsk != tsk_template)
+ set_constraints (decl, get_constraints (fn));
/* DECL is a re-declaration or partial instantiation of a template
function. */
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-spec1.C
b/gcc/testsuite/g++.dg/cpp2a/concepts-spec1.C
new file mode 100644
index 00000000000..5001813d7b7
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-spec1.C
@@ -0,0 +1,10 @@
+// Example from CA 104 proposal.
+// { dg-do compile { target concepts } }
+
+template <class T> concept C = sizeof(T) == 8;
+template <class T> struct A {
+ template <class U> U f(U) requires C<typename T::type>; // #1
+ template <class U> U f(U) requires C<T>; // #2
+};
+
+template <> template <class U> U A<int>::f(U) requires C<int> { } // OK,
specializes #2
diff --git a/gcc/testsuite/g++.dg/template/nontype18.C
b/gcc/testsuite/g++.dg/template/nontype18.C
index cbe0a1b5a0d..b68416dca61 100644
--- a/gcc/testsuite/g++.dg/template/nontype18.C
+++ b/gcc/testsuite/g++.dg/template/nontype18.C
@@ -5,4 +5,4 @@ template<int I> struct A
template<typename T> void foo();
};
-template<int I> template<typename T> void A<0>::foo() {} // { dg-error
"template parameter" }
+template<int I> template<typename T> void A<0>::foo() {} // { dg-error "" }
base-commit: 42e9f80bf4f6a38733c221c03a512c432cdb784f
--
2.18.1
