c++, v2: Implement CWG2635 - Constrained structured bindings
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Commit Message
On Sat, Nov 12, 2022 at 12:23:56PM +0100, Jakub Jelinek wrote:
> The following patch implements CWG2635.
>
> So far tested on
> GXX_TESTSUITE_STDS=98,11,14,17,20,2b make check-g++ RUNTESTFLAGS="dg.exp=decomp*"
> ok for trunk if it passes full bootstrap/regtest and it is voted in?
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.
* g++.dg/cpp2a/decomp5.C: New test.
* g++.dg/cpp2a/concepts-placeholder7.C: Adjust expected diagnostics.
* g++.dg/cpp2a/concepts-placeholder8.C: Likewise.
Jakub
Comments
On 11/13/22 01:50, Jakub Jelinek wrote:
> On Sat, Nov 12, 2022 at 12:23:56PM +0100, Jakub Jelinek wrote:
>> The following patch implements CWG2635.
>>
>> So far tested on
>> GXX_TESTSUITE_STDS=98,11,14,17,20,2b make check-g++ RUNTESTFLAGS="dg.exp=decomp*"
>> ok for trunk if it passes full bootstrap/regtest and it is voted in?
>
> 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.
> * g++.dg/cpp2a/decomp5.C: New test.
> * g++.dg/cpp2a/concepts-placeholder7.C: Adjust expected diagnostics.
> * g++.dg/cpp2a/concepts-placeholder8.C: Likewise.
>
> --- gcc/cp/decl.cc.jj 2022-11-11 17:14:33.103869977 +0100
> +++ gcc/cp/decl.cc 2022-11-12 12:13:52.217239729 +0100
> @@ -12660,7 +12660,8 @@ grokdeclarator (const cp_declarator *dec
> gcc_unreachable ();
> }
> if (TREE_CODE (type) != TEMPLATE_TYPE_PARM
> - || TYPE_IDENTIFIER (type) != auto_identifier)
> + || TYPE_IDENTIFIER (type) != auto_identifier
> + || PLACEHOLDER_TYPE_CONSTRAINTS_INFO (type))
> {
> if (type != error_mark_node)
> {
> --- gcc/testsuite/g++.dg/cpp2a/decomp5.C.jj 2022-11-12 12:17:21.024392082 +0100
> +++ gcc/testsuite/g++.dg/cpp2a/decomp5.C 2022-11-12 12:20:00.700214521 +0100
> @@ -0,0 +1,20 @@
> +// 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 type 'auto \\\[requires ::C<<placeholder>, >\\\]'" }
> + // { dg-message "type must be cv-qualified 'auto' or reference to cv-qualified 'auto'" "" { target *-*-* } .-1 }
> --- gcc/testsuite/g++.dg/cpp2a/concepts-placeholder7.C.jj 2021-04-06 23:49:08.288882716 +0200
> +++ gcc/testsuite/g++.dg/cpp2a/concepts-placeholder7.C 2022-11-13 12:17:38.570047510 +0100
> @@ -7,16 +7,16 @@ 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 type 'auto \\\[requires ::C1<<placeholder>, >\\\]'" }
> + C1 auto [c] = y; // { dg-error "structured binding declaration cannot have type 'auto \\\[requires ::C1<<placeholder>, >\\\]'" }
> }
>
> 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 type 'auto \\\[requires ::C1<<placeholder>, >\\\]'" }
> + C1 auto [c] = y; // { dg-error "structured binding declaration cannot have type 'auto \\\[requires ::C1<<placeholder>, >\\\]'" }
> }
> template void g<int>();
>
> @@ -27,6 +27,6 @@ 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 type 'const auto \\\[requires ::C2<<placeholder>, >\\\]'" }
> }
> template void h<int>();
> --- gcc/testsuite/g++.dg/cpp2a/concepts-placeholder8.C.jj 2021-04-06 23:49:08.288882716 +0200
> +++ gcc/testsuite/g++.dg/cpp2a/concepts-placeholder8.C 2022-11-13 12:19:17.034684881 +0100
> @@ -5,6 +5,6 @@ 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 type 'const auto \\\[requires ::is_const<<placeholder>, >\\\]'" }
> + const is_const auto [c] = y; // { dg-error "structured binding declaration cannot have type 'const auto \\\[requires ::is_const<<placeholder>, >\\\]'" }
> }
>
>
> Jakub
>
@@ -12660,7 +12660,8 @@ grokdeclarator (const cp_declarator *dec
gcc_unreachable ();
}
if (TREE_CODE (type) != TEMPLATE_TYPE_PARM
- || TYPE_IDENTIFIER (type) != auto_identifier)
+ || TYPE_IDENTIFIER (type) != auto_identifier
+ || PLACEHOLDER_TYPE_CONSTRAINTS_INFO (type))
{
if (type != error_mark_node)
{
@@ -0,0 +1,20 @@
+// 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 type 'auto \\\[requires ::C<<placeholder>, >\\\]'" }
+ // { dg-message "type must be cv-qualified 'auto' or reference to cv-qualified 'auto'" "" { target *-*-* } .-1 }
@@ -7,16 +7,16 @@ 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 type 'auto \\\[requires ::C1<<placeholder>, >\\\]'" }
+ C1 auto [c] = y; // { dg-error "structured binding declaration cannot have type 'auto \\\[requires ::C1<<placeholder>, >\\\]'" }
}
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 type 'auto \\\[requires ::C1<<placeholder>, >\\\]'" }
+ C1 auto [c] = y; // { dg-error "structured binding declaration cannot have type 'auto \\\[requires ::C1<<placeholder>, >\\\]'" }
}
template void g<int>();
@@ -27,6 +27,6 @@ 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 type 'const auto \\\[requires ::C2<<placeholder>, >\\\]'" }
}
template void h<int>();
@@ -5,6 +5,6 @@ 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 type 'const auto \\\[requires ::is_const<<placeholder>, >\\\]'" }
+ const is_const auto [c] = y; // { dg-error "structured binding declaration cannot have type 'const auto \\\[requires ::is_const<<placeholder>, >\\\]'" }
}