From: Jason Merrill <jason@redhat.com>
To: Jakub Jelinek <jakub@redhat.com>
Cc: gcc-patches@gcc.gnu.org
Subject: Re: [PATCH] c++, v3: Implement CWG2635 - Constrained structured bindings
Date: Wed, 16 Nov 2022 08:12:17 -0500 [thread overview]
Message-ID: <7f8bee68-f9b9-3c28-cc3d-53d8dbf22198@redhat.com> (raw)
In-Reply-To: <Y3S4wvO/i4rBQPVj@tucnak>
On 11/16/22 05:17, Jakub Jelinek wrote:
> On Tue, Nov 15, 2022 at 06:22:36PM -0500, Jason Merrill wrote:
>>> Here is another version of the patch that passed bootstrap/regtest, the only
>>> change are tweaks to 2 further testcases.
>>>
>>> 2022-11-13 Jakub Jelinek <jakub@redhat.com>
>>>
>>> * decl.cc (grokdeclarator): Implement
>>> CWG2635 - Constrained structured bindings. Diagnose constrained
>>> auto type.
>>
>> Let's make the constrained auto case a pedwarn instead of an error.
>
> So like this (i.e. just pedwarn but don't change the type and keep doing
> what we were before)?
OK.
> 2022-11-16 Jakub Jelinek <jakub@redhat.com>
>
> * decl.cc (grokdeclarator): Implement
> CWG2635 - Constrained structured bindings. Emit a pedwarn on
> constrained auto type. Add auto_diagnostic_group for error_at
> and inform for non-auto type on structured bindings declaration.
>
> * g++.dg/cpp2a/decomp5.C: New test.
> * g++.dg/cpp2a/decomp6.C: New test.
> * g++.dg/cpp2a/decomp7.C: New test.
> * g++.dg/cpp2a/concepts-placeholder7.C: Adjust expected diagnostics.
> * g++.dg/cpp2a/concepts-placeholder8.C: Likewise.
> * g++.dg/cpp2a/concepts-placeholder9.C: New test.
> * g++.dg/cpp2a/concepts-placeholder10.C: New test.
>
> --- gcc/cp/decl.cc.jj 2022-11-16 07:29:11.603716748 +0100
> +++ gcc/cp/decl.cc 2022-11-16 11:07:05.169822071 +0100
> @@ -12664,6 +12664,7 @@ grokdeclarator (const cp_declarator *dec
> {
> if (type != error_mark_node)
> {
> + auto_diagnostic_group d;
> error_at (loc, "structured binding declaration cannot have "
> "type %qT", type);
> inform (loc,
> @@ -12673,6 +12674,10 @@ grokdeclarator (const cp_declarator *dec
> type = build_qualified_type (make_auto (), type_quals);
> declspecs->type = type;
> }
> + else if (PLACEHOLDER_TYPE_CONSTRAINTS_INFO (type))
> + pedwarn (loc, OPT_Wpedantic,
> + "structured binding declaration cannot have constrained "
> + "%<auto%> type %qT", type);
> inlinep = 0;
> typedef_p = 0;
> constexpr_p = 0;
> --- gcc/testsuite/g++.dg/cpp2a/decomp5.C.jj 2022-11-16 10:39:20.469335601 +0100
> +++ gcc/testsuite/g++.dg/cpp2a/decomp5.C 2022-11-16 10:46:02.272896156 +0100
> @@ -0,0 +1,19 @@
> +// CWG2635 - Constrained structured bindings
> +// { dg-do compile { target c++20 } }
> +
> +namespace std {
> + template<typename T> struct tuple_size;
> + template<int, typename> struct tuple_element;
> +}
> +
> +struct A {
> + int i;
> + A(int x) : i(x) {}
> + template <int I> int& get() { return i; }
> +};
> +
> +template<> struct std::tuple_size<A> { static const int value = 2; };
> +template<int I> struct std::tuple_element<I,A> { using type = int; };
> +
> +template<class T> concept C = true;
> +C auto [x, y] = A{1}; // { dg-error "structured binding declaration cannot have constrained 'auto' type 'auto \\\[requires ::C<<placeholder>, >\\\]'" }
> --- gcc/testsuite/g++.dg/cpp2a/decomp6.C.jj 2022-11-16 10:46:44.868319518 +0100
> +++ gcc/testsuite/g++.dg/cpp2a/decomp6.C 2022-11-16 10:47:07.485013348 +0100
> @@ -0,0 +1,20 @@
> +// CWG2635 - Constrained structured bindings
> +// { dg-do compile { target c++20 } }
> +// { dg-options "-pedantic" }
> +
> +namespace std {
> + template<typename T> struct tuple_size;
> + template<int, typename> struct tuple_element;
> +}
> +
> +struct A {
> + int i;
> + A(int x) : i(x) {}
> + template <int I> int& get() { return i; }
> +};
> +
> +template<> struct std::tuple_size<A> { static const int value = 2; };
> +template<int I> struct std::tuple_element<I,A> { using type = int; };
> +
> +template<class T> concept C = true;
> +C auto [x, y] = A{1}; // { dg-warning "structured binding declaration cannot have constrained 'auto' type 'auto \\\[requires ::C<<placeholder>, >\\\]'" }
> --- gcc/testsuite/g++.dg/cpp2a/decomp7.C.jj 2022-11-16 10:47:14.578917309 +0100
> +++ gcc/testsuite/g++.dg/cpp2a/decomp7.C 2022-11-16 10:47:32.061680633 +0100
> @@ -0,0 +1,20 @@
> +// CWG2635 - Constrained structured bindings
> +// { dg-do compile { target c++20 } }
> +// { dg-options "-Wno-pedantic" }
> +
> +namespace std {
> + template<typename T> struct tuple_size;
> + template<int, typename> struct tuple_element;
> +}
> +
> +struct A {
> + int i;
> + A(int x) : i(x) {}
> + template <int I> int& get() { return i; }
> +};
> +
> +template<> struct std::tuple_size<A> { static const int value = 2; };
> +template<int I> struct std::tuple_element<I,A> { using type = int; };
> +
> +template<class T> concept C = true;
> +C auto [x, y] = A{1}; // { dg-bogus "structured binding declaration cannot have constrained 'auto' type 'auto \\\[requires ::C<<placeholder>, >\\\]'" }
> --- gcc/testsuite/g++.dg/cpp2a/concepts-placeholder7.C.jj 2022-11-13 17:53:46.037681901 +0100
> +++ gcc/testsuite/g++.dg/cpp2a/concepts-placeholder7.C 2022-11-16 11:09:56.092513219 +0100
> @@ -7,16 +7,18 @@ template <class>
> void f() {
> int x[] = {1,2};
> int y[] = {3};
> - C1 auto [a,b] = x;
> - C1 auto [c] = y; // { dg-error "constraints" }
> + C1 auto [a,b] = x; // { dg-error "structured binding declaration cannot have constrained 'auto' type 'auto \\\[requires ::C1<<placeholder>, >\\\]'" }
> + C1 auto [c] = y; // { dg-error "structured binding declaration cannot have constrained 'auto' type 'auto \\\[requires ::C1<<placeholder>, >\\\]'" }
> + // { dg-error "constraints" "" { target *-*-* } .-1 }
> }
>
> template <class T>
> void g() {
> T x[] = {1,2};
> T y[] = {3};
> - C1 auto [a,b] = x;
> - C1 auto [c] = y; // { dg-error "constraints" }
> + C1 auto [a,b] = x; // { dg-error "structured binding declaration cannot have constrained 'auto' type 'auto \\\[requires ::C1<<placeholder>, >\\\]'" }
> + C1 auto [c] = y; // { dg-error "structured binding declaration cannot have constrained 'auto' type 'auto \\\[requires ::C1<<placeholder>, >\\\]'" }
> + // { dg-error "constraints" "" { target *-*-* } .-1 }
> }
> template void g<int>();
>
> @@ -27,6 +29,6 @@ struct S { int a, b; } s;
>
> template <class T>
> void h() {
> - const C2<T> auto& [a, b] = s;
> + const C2<T> auto& [a, b] = s; // { dg-error "structured binding declaration cannot have constrained 'auto' type 'const auto \\\[requires ::C2<<placeholder>, >\\\]'" }
> }
> template void h<int>();
> --- gcc/testsuite/g++.dg/cpp2a/concepts-placeholder8.C.jj 2022-11-13 17:53:46.037681901 +0100
> +++ gcc/testsuite/g++.dg/cpp2a/concepts-placeholder8.C 2022-11-16 11:10:25.432116956 +0100
> @@ -5,6 +5,7 @@ template <class T> concept is_const = __
> void f() {
> int x[] = {1,2};
> const int y[] = {3};
> - const is_const auto [a,b] = x; // { dg-error "constraints" }
> - const is_const auto [c] = y;
> + const is_const auto [a,b] = x; // { dg-error "structured binding declaration cannot have constrained 'auto' type 'const auto \\\[requires ::is_const<<placeholder>, >\\\]'" }
> + // { dg-error "constraints" "" { target *-*-* } .-1 }
> + const is_const auto [c] = y; // { dg-error "structured binding declaration cannot have constrained 'auto' type 'const auto \\\[requires ::is_const<<placeholder>, >\\\]'" }
> }
> --- gcc/testsuite/g++.dg/cpp2a/concepts-placeholder9.C.jj 2022-11-16 10:49:54.610750873 +0100
> +++ gcc/testsuite/g++.dg/cpp2a/concepts-placeholder9.C 2022-11-16 11:12:09.234715037 +0100
> @@ -0,0 +1,33 @@
> +// PR c++/99899
> +// { dg-do compile { target c++20 } }
> +// { dg-options "-Wno-pedantic" }
> +
> +template <class T> concept C1 = sizeof(T) > sizeof(int[1]);
> +
> +template <class>
> +void f() {
> + int x[] = {1,2};
> + int y[] = {3};
> + C1 auto [a,b] = x;
> + C1 auto [c] = y; // { dg-error "constraints" }
> +}
> +
> +template <class T>
> +void g() {
> + T x[] = {1,2};
> + T y[] = {3};
> + C1 auto [a,b] = x;
> + C1 auto [c] = y; // { dg-error "constraints" }
> +}
> +template void g<int>();
> +
> +
> +template <class... Ts> concept C2 = sizeof...(Ts) > 1;
> +
> +struct S { int a, b; } s;
> +
> +template <class T>
> +void h() {
> + const C2<T> auto& [a, b] = s;
> +}
> +template void h<int>();
> --- gcc/testsuite/g++.dg/cpp2a/concepts-placeholder10.C.jj 2022-11-16 10:49:54.610750873 +0100
> +++ gcc/testsuite/g++.dg/cpp2a/concepts-placeholder10.C 2022-11-16 10:50:16.757451058 +0100
> @@ -0,0 +1,11 @@
> +// { dg-do compile { target c++20 } }
> +// { dg-options "-Wno-pedantic" }
> +
> +template <class T> concept is_const = __is_same(T, const T);
> +
> +void f() {
> + int x[] = {1,2};
> + const int y[] = {3};
> + const is_const auto [a,b] = x; // { dg-error "constraints" }
> + const is_const auto [c] = y;
> +}
>
> Jakub
>
prev parent reply other threads:[~2022-11-16 13:12 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-12 11:23 [PATCH] c++: " Jakub Jelinek
2022-11-13 11:50 ` [PATCH] c++, v2: " Jakub Jelinek
2022-11-15 23:22 ` Jason Merrill
2022-11-16 10:17 ` [PATCH] c++, v3: " Jakub Jelinek
2022-11-16 13:12 ` Jason Merrill [this message]
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