On Fri, Jun 26, 2020 at 04:19:08PM -0400, Jason Merrill wrote:
> Please also test scoped enum.
Here:
-- >8 --
95568 complains that CTAD for aggregates doesn't work within
requires-clause and it turned out that it doesn't work when we try
the deduction in a template. The reason is that maybe_aggr_guide
creates a guide that can look like this
template<class T> X(decltype (X<T>::x))-> X<T>
where the parameter is a decltype, which is a non-deduced context. So
the subsequent build_new_function_call fails because unify_one_argument
can't deduce anything from it ([temp.deduct.type]: "If a template
parameter is used only in non-deduced contexts and is not explicitly
specified, template argument deduction fails.")
Those decltypes come from finish_decltype_type. We can just use
TREE_TYPE instead. I pondered using unlowered_expr_type, but that
didn't make any difference for the FIELD_DECLs I saw in
class-deduction-aggr6.C.
gcc/cp/ChangeLog:
PR c++/95568
* pt.c (collect_ctor_idx_types): Use TREE_TYPE.
gcc/testsuite/ChangeLog:
PR c++/95568
* g++.dg/cpp2a/class-deduction-aggr5.C: New test.
* g++.dg/cpp2a/class-deduction-aggr6.C: New test.
---
gcc/cp/pt.c | 2 +-
.../g++.dg/cpp2a/class-deduction-aggr5.C | 20 +++++++++++
.../g++.dg/cpp2a/class-deduction-aggr6.C | 35 +++++++++++++++++++
3 files changed, 56 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/g++.dg/cpp2a/class-deduction-aggr5.C
create mode 100644 gcc/testsuite/g++.dg/cpp2a/class-deduction-aggr6.C
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 53a64c3a15e..618bf68b2d6 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -28329,7 +28329,7 @@ collect_ctor_idx_types (tree ctor, tree list, tree elt
= NULL_TREE)
tree idx, val; unsigned i;
FOR_EACH_CONSTRUCTOR_ELT (v, i, idx, val)
{
- tree ftype = elt ? elt : finish_decltype_type (idx, true, tf_none);
+ tree ftype = elt ? elt : TREE_TYPE (idx);
if (BRACE_ENCLOSED_INITIALIZER_P (val)
&& CONSTRUCTOR_NELTS (val)
/* As in reshape_init_r, a non-aggregate or array-of-dependent-bound
diff --git a/gcc/testsuite/g++.dg/cpp2a/class-deduction-aggr5.C
b/gcc/testsuite/g++.dg/cpp2a/class-deduction-aggr5.C
new file mode 100644
index 00000000000..01253f42006
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/class-deduction-aggr5.C
@@ -0,0 +1,20 @@
+// PR c++/95568
+// { dg-do compile { target c++20 } }
+
+template<typename T> struct X { T x; };
+template<typename T, typename U> struct X2 { T x; U y; };
+template<typename T> concept Y = requires { X{0}; };
+
+template<typename T>
+void g()
+{
+ X{0};
+ X2{1, 2.2};
+ Y auto y = X{1};
+}
+
+void
+fn ()
+{
+ g<int>();
+}
diff --git a/gcc/testsuite/g++.dg/cpp2a/class-deduction-aggr6.C
b/gcc/testsuite/g++.dg/cpp2a/class-deduction-aggr6.C
new file mode 100644
index 00000000000..95d7c5eec18
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/class-deduction-aggr6.C
@@ -0,0 +1,35 @@
+// PR c++/95568
+// { dg-do compile { target c++20 } }
+// CTAD with aggregates containing bit-fields.
+
+template<class, class> struct same_type;
+template<class T> struct same_type<T, T> {};
+
+enum E { e };
+enum class F { f };
+
+template<typename T>
+struct X {
+ T a : 5;
+};
+
+template<typename>
+void g()
+{
+ auto x = X{ 0 };
+ same_type<decltype(x.a), int>();
+ auto x2 = X{ E::e };
+ same_type<decltype(x2.a), E>();
+ auto x3 = X{ false };
+ same_type<decltype(x3.a), bool>();
+ auto x4 = X{ 0u };
+ same_type<decltype(x4.a), unsigned int>();
+ auto x5 = X{ F::f };
+ same_type<decltype(x5.a), F>();
+}
+
+void
+fn ()
+{
+ g<int>();
+}
base-commit: 0801f419440c14f6772b28f763ad7d40f7f7a580
--
2.26.2
