On 1/11/21 8:08 PM, Patrick Palka wrote:
On Mon, 11 Jan 2021, Jason Merrill wrote:
On 1/9/21 5:23 PM, Patrick Palka wrote:
This patch teaches find_template_parameters to visit the template
represented by a CTAD placeholder, which is normally not visited by
for_each_template_parm. This template may be a template template
parameter (as in the first testcase), or it may implicitly use the
template parameters of an enclosing class template (as in the second
testcase), and in either case we need to record the template parameters
used therein for later satisfaction.
Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
trunk and perhaps the 10 branch? Also tested on range-v3 and cmcstl2.
gcc/cp/ChangeLog:
PR c++/98611
* pt.c (any_template_parm_r) <case TEMPLATE_TYPE_PARM>: Visit
the template of a CTAD placeholder.
Did you consider doing this in cp_walk_subtrees instead of here?
Briefly, but I couldn't convince myself which of the three visitors
(cp_walk_subtrees, for_each_template_parm_r or any_template_parm_r) is
the most appropriate place to do it in, so I defaulted to the most
specific routine of the three.
The following passes bootstrap and regtesting on x86_64-pc-linux-gnu.
Shall we go with this?
I think so; a class template placeholder is written explicitly in
whatever we're walking over, so looking at it here makes sense to me.
The patch is OK.
-- >8 --
gcc/cp/ChangeLog:
PR c++/98611
* tree.c (cp_walk_subtrees) <case TEMPLATE_TYPE_PARM>: Visit
the template of a CTAD placeholder.
gcc/testsuite/ChangeLog:
PR c++/98611
* g++.dg/cpp2a/concepts-ctad1.C: New test.
* g++.dg/cpp2a/concepts-ctad2.C: New test.
---
gcc/cp/tree.c | 5 ++++-
gcc/testsuite/g++.dg/cpp2a/concepts-ctad1.C | 16 ++++++++++++++++
gcc/testsuite/g++.dg/cpp2a/concepts-ctad2.C | 13 +++++++++++++
3 files changed, 33 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-ctad1.C
create mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-ctad2.C
diff --git a/gcc/cp/tree.c b/gcc/cp/tree.c
index c536eb581a7..d339036e88e 100644
--- a/gcc/cp/tree.c
+++ b/gcc/cp/tree.c
@@ -5173,12 +5173,15 @@ cp_walk_subtrees (tree *tp, int *walk_subtrees_p,
walk_tree_fn func,
result = NULL_TREE;
switch (code)
{
+ case TEMPLATE_TYPE_PARM:
+ if (template_placeholder_p (*tp))
+ WALK_SUBTREE (CLASS_PLACEHOLDER_TEMPLATE (*tp));
+ /* Fall through. */
case DEFERRED_PARSE:
case TEMPLATE_TEMPLATE_PARM:
case BOUND_TEMPLATE_TEMPLATE_PARM:
case UNBOUND_CLASS_TEMPLATE:
case TEMPLATE_PARM_INDEX:
- case TEMPLATE_TYPE_PARM:
case TYPEOF_TYPE:
case UNDERLYING_TYPE:
/* None of these have subtrees other than those already walked
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-ctad1.C
b/gcc/testsuite/g++.dg/cpp2a/concepts-ctad1.C
new file mode 100644
index 00000000000..ec2e4b014d7
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-ctad1.C
@@ -0,0 +1,16 @@
+// PR c++/98611
+// { dg-do compile { target c++20 } }
+
+template <class T, class U>
+concept IsSame = __is_same(T, U);
+
+template <class T, template <class...> class _Class>
+concept IsInstantiationOf = requires(T object) {
+ { _Class{object} } -> IsSame<T>;
+};
+
+template <class T> struct Degrees {};
+static_assert(IsInstantiationOf<Degrees<int>, Degrees>);
+
+template <class T> struct NotDegrees {};
+static_assert(!IsInstantiationOf<Degrees<int>, NotDegrees>);
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-ctad2.C
b/gcc/testsuite/g++.dg/cpp2a/concepts-ctad2.C
new file mode 100644
index 00000000000..0d7f9790777
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-ctad2.C
@@ -0,0 +1,13 @@
+// PR c++/98611
+// { dg-do compile { target c++20 } }
+
+template <class>
+struct S {
+ template <class T> struct Tmpl { Tmpl(T); };
+
+ template <class T>
+ requires requires (T object) { Tmpl{object}; }
+ static int f(T);
+};
+
+int a = S<int>::f(0);
