On Tue, Dec 28, 2021 at 10:08 AM Patrick Palka <ppa...@redhat.com> wrote:
>
> Here during satisfaction of B's associated constraints we're failing to
> reject the object-less call to the non-static member function A::size
> ultimately because satisfaction is performed in the (access) context of
> the class template B, which has a dependent bases, and so the
> any_dependent_bases_p check within build_new_method_call causes us to
> avoid rejecting the call.
>
> This patch fixes this by refining the any_dependent_bases_p check within
> build_new_method_call: dependent bases can't make a difference for
> resolving the implicit object parameter if we're in a conext where
> 'this' is unavailable, so let's check current_class_ptr too.
>
> Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
> trunk and perhaps 11? The first testcase exhibits a regression
> introduced by r12-1937.
D'oh, never mind about the backport request since this is at worst a
12 regression.
>
> PR c++/103831
>
> gcc/cp/ChangeLog:
>
> * call.c (build_new_method_call): Consider dependent bases only
> if 'this' is available.
>
> gcc/testsuite/ChangeLog:
>
> * g++.dg/cpp2a/concepts-class3.C: New test.
> * g++.dg/template/non-dependent18.C: New test.
> ---
> gcc/cp/call.c | 2 +-
> gcc/testsuite/g++.dg/cpp2a/concepts-class3.C | 12 ++++++++++++
> .../g++.dg/template/non-dependent18.C | 19 +++++++++++++++++++
> 3 files changed, 32 insertions(+), 1 deletion(-)
> create mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-class3.C
> create mode 100644 gcc/testsuite/g++.dg/template/non-dependent18.C
>
> diff --git a/gcc/cp/call.c b/gcc/cp/call.c
> index bee367f57d7..3da9e7a6284 100644
> --- a/gcc/cp/call.c
> +++ b/gcc/cp/call.c
> @@ -11098,7 +11098,7 @@ build_new_method_call (tree instance, tree fns,
> vec<tree, va_gc> **args,
> we know we really need it. */
> cand->first_arg = instance;
> }
> - else if (any_dependent_bases_p ())
> + else if (current_class_ptr && any_dependent_bases_p ())
> /* We can't tell until instantiation time whether we can use
> *this as the implicit object argument. */;
> else
> diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-class3.C
> b/gcc/testsuite/g++.dg/cpp2a/concepts-class3.C
> new file mode 100644
> index 00000000000..68b50b71278
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp2a/concepts-class3.C
> @@ -0,0 +1,12 @@
> +// PR c++/103831
> +// { dg-do compile { target c++20 } }
> +
> +struct A {
> + constexpr int size() { return 42; } // non-static
> +};
> +
> +template<class T>
> + requires (T::size() == 42) // { dg-error "without object" }
> +struct B : T { };
> +
> +template struct B<A>; // { dg-error "constraint" }
> diff --git a/gcc/testsuite/g++.dg/template/non-dependent18.C
> b/gcc/testsuite/g++.dg/template/non-dependent18.C
> new file mode 100644
> index 00000000000..7fe623d497f
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/template/non-dependent18.C
> @@ -0,0 +1,19 @@
> +// PR c++/103831
> +// { dg-do compile { target c++11 } }
> +
> +struct A {
> + constexpr int size() { return 42; } // non-static
> +};
> +
> +template<class T>
> +struct B : T {
> + static_assert(A::size() == 42); // { dg-error "without object" }
> +
> + static int f() {
> + static_assert(A::size() == 42, ""); // { dg-error "without object" }
> + return A::size(); // { dg-error "without object" }
> + }
> +
> + int n = A::size();
> + static const int m = A::size(); // { dg-error "without object" }
> +};
> --
> 2.34.1.390.g2ae0a9cb82
>
