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* [gcc r12-8602] c++: don't substitute TEMPLATE_PARM_CONSTRAINTS [PR100374]
@ 2022-07-21 16:48 Patrick Palka
0 siblings, 0 replies; only message in thread
From: Patrick Palka @ 2022-07-21 16:48 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:90655e30130f8f609911335902db3c8354a5e21a
commit r12-8602-g90655e30130f8f609911335902db3c8354a5e21a
Author: Patrick Palka <ppalka@redhat.com>
Date: Fri Jun 3 09:29:12 2022 -0400
c++: don't substitute TEMPLATE_PARM_CONSTRAINTS [PR100374]
This patch makes us avoid substituting into the TEMPLATE_PARM_CONSTRAINTS
of each template parameter except as necessary for declaration matching,
like we already do for the other constituent constraints of a declaration.
This patch also improves the CA104 implementation of explicit
specialization matching of a constrained function template inside a
class template, by considering the function's combined constraints
instead of just its trailing constraints. This allows us to correctly
handle the first three explicit specializations in concepts-spec2.C
below, but because we compare the constraints as a whole, it means we
incorrectly accept the fourth explicit specialization which writes #3's
constraints in a different way. For complete correctness here,
determine_specialization should use tsubst_each_template_parm_constraints
and template_parameter_heads_equivalent_p.
PR c++/100374
gcc/cp/ChangeLog:
* pt.cc (determine_specialization): Compare overall constraints
not just the trailing constraints.
(tsubst_each_template_parm_constraints): Define.
(tsubst_friend_function): Use it.
(tsubst_friend_class): Use it.
(tsubst_template_parm): Don't substitute TEMPLATE_PARM_CONSTRAINTS.
gcc/testsuite/ChangeLog:
* g++.dg/cpp2a/concepts-spec2.C: New test.
* g++.dg/cpp2a/concepts-template-parm11.C: New test.
(cherry picked from commit 43c013df02fdb07f9b7a5e7e6669e6d69769d451)
Diff:
---
gcc/cp/pt.cc | 45 ++++++++++++++++++----
gcc/testsuite/g++.dg/cpp2a/concepts-spec2.C | 16 ++++++++
.../g++.dg/cpp2a/concepts-template-parm11.C | 20 ++++++++++
3 files changed, 74 insertions(+), 7 deletions(-)
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 8440286c1ad..b2b1a5d1ec6 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -184,6 +184,7 @@ static int unify_pack_expansion (tree, tree, tree,
tree, unification_kind_t, bool, bool);
static tree copy_template_args (tree);
static tree tsubst_template_parms (tree, tree, tsubst_flags_t);
+static void tsubst_each_template_parm_constraints (tree, tree, tsubst_flags_t);
tree most_specialized_partial_spec (tree, tsubst_flags_t);
static tree tsubst_aggr_type (tree, tree, tsubst_flags_t, tree, int);
static tree tsubst_arg_types (tree, tree, tree, tsubst_flags_t, tree);
@@ -2323,8 +2324,8 @@ determine_specialization (tree template_id,
if (!compparms (fn_arg_types, decl_arg_types))
continue;
- tree freq = get_trailing_function_requirements (fn);
- tree dreq = get_trailing_function_requirements (decl);
+ tree freq = get_constraints (fn);
+ tree dreq = get_constraints (decl);
if (!freq != !dreq)
continue;
if (freq)
@@ -2333,7 +2334,7 @@ determine_specialization (tree template_id,
constraint-expression. */
tree fargs = DECL_TI_ARGS (fn);
tsubst_flags_t complain = tf_none;
- freq = tsubst_constraint (freq, fargs, complain, fn);
+ freq = tsubst_constraint_info (freq, fargs, complain, fn);
if (!cp_tree_equal (freq, dreq))
continue;
}
@@ -11279,7 +11280,13 @@ tsubst_friend_function (tree decl, tree args)
tree parms = DECL_TEMPLATE_PARMS (new_friend);
tree treqs = TEMPLATE_PARMS_CONSTRAINTS (parms);
treqs = maybe_substitute_reqs_for (treqs, new_friend);
- TEMPLATE_PARMS_CONSTRAINTS (parms) = treqs;
+ if (treqs != TEMPLATE_PARMS_CONSTRAINTS (parms))
+ {
+ TEMPLATE_PARMS_CONSTRAINTS (parms) = treqs;
+ /* As well as each TEMPLATE_PARM_CONSTRAINTS. */
+ tsubst_each_template_parm_constraints (parms, args,
+ tf_warning_or_error);
+ }
}
/* The mangled name for the NEW_FRIEND is incorrect. The function
@@ -11525,6 +11532,8 @@ tsubst_friend_class (tree friend_tmpl, tree args)
{
tree parms = tsubst_template_parms (DECL_TEMPLATE_PARMS (friend_tmpl),
args, tf_warning_or_error);
+ tsubst_each_template_parm_constraints (parms, args,
+ tf_warning_or_error);
location_t saved_input_location = input_location;
input_location = DECL_SOURCE_LOCATION (friend_tmpl);
tree cons = get_constraints (tmpl);
@@ -11559,6 +11568,8 @@ tsubst_friend_class (tree friend_tmpl, tree args)
DECL_FRIEND_CONTEXT (friend_tmpl));
--processing_template_decl;
set_constraints (tmpl, ci);
+ tsubst_each_template_parm_constraints (DECL_TEMPLATE_PARMS (tmpl),
+ args, tf_warning_or_error);
}
/* Inject this template into the enclosing namspace scope. */
@@ -13681,7 +13692,6 @@ tsubst_template_parm (tree t, tree args, tsubst_flags_t complain)
default_value = TREE_PURPOSE (t);
parm_decl = TREE_VALUE (t);
- tree constraint = TEMPLATE_PARM_CONSTRAINTS (t);
parm_decl = tsubst (parm_decl, args, complain, NULL_TREE);
if (TREE_CODE (parm_decl) == PARM_DECL
@@ -13689,13 +13699,34 @@ tsubst_template_parm (tree t, tree args, tsubst_flags_t complain)
parm_decl = error_mark_node;
default_value = tsubst_template_arg (default_value, args,
complain, NULL_TREE);
- constraint = tsubst_constraint (constraint, args, complain, NULL_TREE);
tree r = build_tree_list (default_value, parm_decl);
- TEMPLATE_PARM_CONSTRAINTS (r) = constraint;
+ TEMPLATE_PARM_CONSTRAINTS (r) = TEMPLATE_PARM_CONSTRAINTS (t);
return r;
}
+/* Substitute in-place the TEMPLATE_PARM_CONSTRAINTS of each template
+ parameter in PARMS for sake of declaration matching. */
+
+static void
+tsubst_each_template_parm_constraints (tree parms, tree args,
+ tsubst_flags_t complain)
+{
+ ++processing_template_decl;
+ for (; parms; parms = TREE_CHAIN (parms))
+ {
+ tree level = TREE_VALUE (parms);
+ for (int i = 0; i < TREE_VEC_LENGTH (level); ++i)
+ {
+ tree parm = TREE_VEC_ELT (level, i);
+ TEMPLATE_PARM_CONSTRAINTS (parm)
+ = tsubst_constraint (TEMPLATE_PARM_CONSTRAINTS (parm), args,
+ complain, NULL_TREE);
+ }
+ }
+ --processing_template_decl;
+}
+
/* Substitute the ARGS into the indicated aggregate (or enumeration)
type T. If T is not an aggregate or enumeration type, it is
handled as if by tsubst. IN_DECL is as for tsubst. If
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-spec2.C b/gcc/testsuite/g++.dg/cpp2a/concepts-spec2.C
new file mode 100644
index 00000000000..4de07352c27
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-spec2.C
@@ -0,0 +1,16 @@
+// { dg-do compile { target c++20 } }
+
+template<class T, int> concept C = true;
+
+template<class T> struct A {
+ template<C<sizeof(T)> U> void f(); // #1
+ template<C<0> U> void f(); // #2
+ template<C<-1> U> void f(); // #3
+};
+
+constexpr int n = sizeof(int);
+template<> template<C<n> U> void A<int>::f() { } // matches #1
+template<> template<C<0> U> void A<int>::f() { } // matches #2
+template<> template<C<-2> U> void A<int>::f() { } // no match { dg-error "match" }
+template<> template<class U> void A<int>::f() requires C<U, -1> { } // shouldn't match #3
+// { dg-error "match" "" { xfail *-*-* } .-1 }
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-template-parm11.C b/gcc/testsuite/g++.dg/cpp2a/concepts-template-parm11.C
new file mode 100644
index 00000000000..498e3c175cf
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-template-parm11.C
@@ -0,0 +1,20 @@
+// PR c++/100374
+// { dg-do compile { target c++20 } }
+
+template<class T, class U>
+concept C = requires { typename T; };
+
+template<class T>
+struct A {
+ template<C<typename T::value_type> U>
+ void f();
+
+ template<C<typename T::value_type> U>
+ struct B;
+};
+
+int main() {
+ A<int> a;
+ a.f<void>();
+ using type = A<int>::B<void>;
+}
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