Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
trunk and perhaps backports?
-- >8 --
In order to compare the constraints of a ttp with that of its argument,
we rewrite the ttp's constraints in terms of the argument template's
template parameters. The substitution to achieve this currently uses a
single level of template arguments, but that never does the right thing
because a ttp's template parameters always have level >= 2. This patch
fixes this by including the outer template arguments in this substitution,
which ought to match the depth of the ttp.
The second testcase demonstrates that it's sometimes necessary to
substitute the concrete outer template arguments instead of generic
ones, because a ttp's constraints could depend on outer arguments.
PR c++/111485
gcc/cp/ChangeLog:
* pt.cc (is_compatible_template_arg): New parameter 'args'.
Add the outer template arguments 'args' to 'new_args'.
(convert_template_argument): Pass 'args' to
is_compatible_template_arg.
gcc/testsuite/ChangeLog:
* g++.dg/cpp2a/concepts-ttp5.C: New test.
* g++.dg/cpp2a/concepts-ttp6.C: New test.
---
gcc/cp/pt.cc | 5 +++--
gcc/testsuite/g++.dg/cpp2a/concepts-ttp5.C | 24 ++++++++++++++++++++++
gcc/testsuite/g++.dg/cpp2a/concepts-ttp6.C | 17 +++++++++++++++
3 files changed, 44 insertions(+), 2 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-ttp5.C
create mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-ttp6.C
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 8758e218ce4..f47887291a6 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -8360,7 +8360,7 @@ canonicalize_expr_argument (tree arg, tsubst_flags_t
complain)
constrained than the parameter. */
static bool
-is_compatible_template_arg (tree parm, tree arg)
+is_compatible_template_arg (tree parm, tree arg, tree args)
{
tree parm_cons = get_constraints (parm);
@@ -8381,6 +8381,7 @@ is_compatible_template_arg (tree parm, tree arg)
{
tree aparms = DECL_INNERMOST_TEMPLATE_PARMS (arg);
new_args = template_parms_level_to_args (aparms);
+ new_args = add_to_template_args (args, new_args);
++processing_template_decl;
parm_cons = tsubst_constraint_info (parm_cons, new_args,
tf_none, NULL_TREE);
@@ -8635,7 +8636,7 @@ convert_template_argument (tree parm,
// Check that the constraints are compatible before allowing the
// substitution.
if (val != error_mark_node)
- if (!is_compatible_template_arg (parm, arg))
+ if (!is_compatible_template_arg (parm, arg, args))
{
if (in_decl && (complain & tf_error))
{
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-ttp5.C
b/gcc/testsuite/g++.dg/cpp2a/concepts-ttp5.C
new file mode 100644
index 00000000000..4129e9e1303
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-ttp5.C
@@ -0,0 +1,24 @@
+// PR c++/111485
+// { dg-do compile { target c++20 } }
+
+template<class T> constexpr bool always_true = true;
+
+template<class T> concept C = always_true<T>;
+template<class T> concept D = C<T> || true;
+
+template<template<C> class TT> struct example { };
+template<template<D> class UU> using example_t = example<UU>;
+
+template<class T>
+struct A {
+ template<template<C> class TT> struct example { };
+
+ template<template<D> class UU> using example_t = example<UU>;
+
+ template<class U>
+ struct B {
+ template<template<D> class UU> using example_t = example<UU>;
+ };
+};
+
+template struct A<int>::B<int>;
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-ttp6.C
b/gcc/testsuite/g++.dg/cpp2a/concepts-ttp6.C
new file mode 100644
index 00000000000..7832cabc7d8
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-ttp6.C
@@ -0,0 +1,17 @@
+// PR c++/111485
+// { dg-do compile { target c++20 } }
+
+template<class T, bool V> constexpr bool always_true = true;
+
+template<class T, bool V> concept C = always_true<T, V>;
+
+template<bool V, template<class T> requires C<T, V> class TT>
+void f();
+
+template<class T> requires C<T, true>
+struct A;
+
+int main() {
+ f<true, A>();
+ f<false, A>(); // { dg-error "no match|constraint" }
+}
--
2.42.0.216.gbda494f404
