Ping.
On Fri, Feb 12, 2021 at 06:12:12PM -0500, Marek Polacek via Gcc-patches wrote:
> We represent deduction guides with FUNCTION_DECLs, but they are built
> without DECL_CONTEXT, leading to an ICE in type_dependent_expression_p
> on the assert that the type of a function template with no dependent
> (innermost!) template arguments must be non-dependent. Consider the
> attached class-deduction79.C: we create a deduction guide:
>
> template<class T> G(T)-> E<Z>::G<T>
>
> we deduce T and create a partial instantiation:
>
> G(T) -> E<Z>::G<T> [with T = int]
>
> And then do_class_deduction wants to create a CALL_EXPR from the above
> using build_new_function_call -> build_over_call which calls mark_used
> -> maybe_instantiate_noexcept -> type_dependent_expression_p.
>
> There, the innermost template arguments are non-dependent (<int>), but
> the fntype is dependent -- the return type is a TYPENAME_TYPE, and
> since we have no DECL_CONTEXT, this check holds:
>
> /* Otherwise, if the function decl isn't from a dependent scope, it can't be
> type-dependent. Checking this is important for functions with auto
> return
> type, which looks like a dependent type. */
> if (TREE_CODE (expression) == FUNCTION_DECL
> && !(DECL_CLASS_SCOPE_P (expression)
> && dependent_type_p (DECL_CONTEXT (expression)))
>
> whereupon we ICE.
>
> Experiments with setting DECL_CONTEXT didn't pan out. So perhaps we
> just want to skip the assert for deduction guides, because they are
> a little special. Better ideas solicited.
>
> Bootstrapped/regtested on x86_64-pc-linux-gnu.
>
> gcc/cp/ChangeLog:
>
> PR c++/97034
> PR c++/99009
> * pt.c (type_dependent_expression_p): Don't assert that the type
> of a deduction guide must non-dependent.
>
> gcc/testsuite/ChangeLog:
>
> PR c++/97034
> PR c++/99009
> * g++.dg/cpp1z/class-deduction79.C: New test.
> * g++.dg/cpp1z/class-deduction80.C: New test.
> * g++.dg/cpp2a/class-deduction-aggr8.C: New test.
> * g++.dg/cpp2a/class-deduction-aggr9.C: New test.
> ---
> gcc/cp/pt.c | 5 ++++-
> .../g++.dg/cpp1z/class-deduction79.C | 20 +++++++++++++++++++
> .../g++.dg/cpp1z/class-deduction80.C | 12 +++++++++++
> .../g++.dg/cpp2a/class-deduction-aggr8.C | 19 ++++++++++++++++++
> .../g++.dg/cpp2a/class-deduction-aggr9.C | 18 +++++++++++++++++
> 5 files changed, 73 insertions(+), 1 deletion(-)
> create mode 100644 gcc/testsuite/g++.dg/cpp1z/class-deduction79.C
> create mode 100644 gcc/testsuite/g++.dg/cpp1z/class-deduction80.C
> create mode 100644 gcc/testsuite/g++.dg/cpp2a/class-deduction-aggr8.C
> create mode 100644 gcc/testsuite/g++.dg/cpp2a/class-deduction-aggr9.C
>
> diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
> index 60de8e93ff7..3e6f3407d40 100644
> --- a/gcc/cp/pt.c
> +++ b/gcc/cp/pt.c
> @@ -27282,7 +27282,10 @@ type_dependent_expression_p (tree expression)
> && DECL_UNIQUE_FRIEND_P (expression)
> && (!DECL_FRIEND_CONTEXT (expression)
> || dependent_type_p (DECL_FRIEND_CONTEXT (expression))))
> - && !DECL_LOCAL_DECL_P (expression))
> + && !DECL_LOCAL_DECL_P (expression)
> + /* We build deduction guides without any DECL_CONTEXT, but they can
> + be type-dependent. */
> + && !deduction_guide_p (expression))
> {
> gcc_assert (!dependent_type_p (TREE_TYPE (expression))
> || undeduced_auto_decl (expression));
> diff --git a/gcc/testsuite/g++.dg/cpp1z/class-deduction79.C
> b/gcc/testsuite/g++.dg/cpp1z/class-deduction79.C
> new file mode 100644
> index 00000000000..86a68248157
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp1z/class-deduction79.C
> @@ -0,0 +1,20 @@
> +// PR c++/97034
> +// { dg-do compile { target c++17 } }
> +
> +template <typename Z>
> +struct E {
> + template <typename T>
> + struct G {
> + T t;
> + G(T) { }
> + };
> +
> + void fn() { G{1}; }
> +};
> +
> +void
> +g ()
> +{
> + E<int> e;
> + e.fn ();
> +}
> diff --git a/gcc/testsuite/g++.dg/cpp1z/class-deduction80.C
> b/gcc/testsuite/g++.dg/cpp1z/class-deduction80.C
> new file mode 100644
> index 00000000000..238024c508f
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp1z/class-deduction80.C
> @@ -0,0 +1,12 @@
> +// PR c++/99009
> +// { dg-do compile { target c++17 } }
> +
> +template<typename> struct B {
> + B(int = A()) {}
> + template <typename ...> struct A;
> +};
> +
> +template<typename T> struct X {
> + template <T...> struct Y;
> + X() { Y y; };
> +};
> diff --git a/gcc/testsuite/g++.dg/cpp2a/class-deduction-aggr8.C
> b/gcc/testsuite/g++.dg/cpp2a/class-deduction-aggr8.C
> new file mode 100644
> index 00000000000..399061100ae
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp2a/class-deduction-aggr8.C
> @@ -0,0 +1,19 @@
> +// PR c++/97034
> +// { dg-do compile { target c++20 } }
> +
> +namespace N {
> +template <typename, typename> struct S {
> + template <typename T, typename U> S(T, U);
> +};
> +} // namespace N
> +template <int> struct E {
> + template <typename T> struct G { T t; };
> + void fn() { G{N::S<char, int>{'a', 1}}; }
> +};
> +
> +void
> +g ()
> +{
> + E<1> e;
> + e.fn ();
> +}
> diff --git a/gcc/testsuite/g++.dg/cpp2a/class-deduction-aggr9.C
> b/gcc/testsuite/g++.dg/cpp2a/class-deduction-aggr9.C
> new file mode 100644
> index 00000000000..245a04cd5f9
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp2a/class-deduction-aggr9.C
> @@ -0,0 +1,18 @@
> +// PR c++/97034
> +// { dg-do compile { target c++20 } }
> +
> +template<typename>
> +struct E {
> + template <typename T>
> + struct G {
> + T t;
> + };
> +
> + void fn() { G{1}; }
> +};
> +
> +void
> +g () {
> + E<int> e;
> + e.fn ();
> +}
>
> base-commit: eb64b0b285b4fda9e8eeda4c2f370e636b1ab2ae
> --
> 2.29.2
>
Marek
