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 <ja...@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)?
2022-11-16 Jakub Jelinek <ja...@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
