c++: Handle auto(x) in parameter-declaration-clause [PR103401]
In C++23, auto(x) is valid, so decltype(auto(x)) should also be valid, so void f(decltype(auto(0))); should be just as void f(int); but currently, everytime we see 'auto' in a parameter-declaration-clause, we try to synthesize_implicit_template_parm for it, creating a new template parameter list. The code above actually has us calling s_i_t_p twice; once from cp_parser_decltype_expr -> cp_parser_postfix_expression which fails and then again from cp_parser_decltype_expr -> cp_parser_expression. So it looks like we have f<auto, auto> and we accept ill-formed code. This shows that we need to be more careful about synthesizing the implicit template parameter. [dcl.spec.auto.general] says that "A placeholder-type-specifier of the form type-constraintopt auto can be used as a decl-specifier of the decl-specifier-seq of a parameter-declaration of a function declaration or lambda-expression..." so this patch turns off auto_is_... after we've parsed the decl-specifier-seq. That doesn't quite cut it yet though, because we also need to handle an auto nested in the decl-specifier: void f(decltype(new auto{0})); therefore the cp_parser_decltype change. To accept "sizeof(auto{10})", the cp_parser_type_id_1 hunk only gives a hard error when we're not parsing tentatively. The cp_parser_parameter_declaration hunk broke lambda-generic-85713-2.C but I think the error we issue with this patch is in fact correct, and clang++ agrees. The r11-1913 change is OK: we need to make sure that we see '(auto)' after decltype to go ahead with 'decltype(auto)'. PR c++/103401 gcc/cp/ChangeLog: * parser.c (cp_parser_decltype): Clear auto_is_implicit_function_template_parm_p. (cp_parser_type_id_1): Give errors only when !cp_parser_simulate_error. (cp_parser_parameter_declaration): Clear auto_is_implicit_function_template_parm_p after parsing the decl-specifier-seq. (cp_parser_sizeof_operand): Clear auto_is_implicit_function_template_parm_p. gcc/testsuite/ChangeLog: * g++.dg/cpp1y/lambda-generic-85713-2.C: Add dg-error. * g++.dg/cpp1y/pr60054.C: Adjust dg-error. * g++.dg/cpp1y/pr60332.C: Likewise. * g++.dg/cpp2a/concepts-pr84979-2.C: Likewise. * g++.dg/cpp2a/concepts-pr84979-3.C: Likewise. * g++.dg/cpp2a/concepts-pr84979.C: Likewise. * g++.dg/cpp23/auto-fncast7.C: New test. * g++.dg/cpp23/auto-fncast8.C: New test. * g++.dg/cpp23/auto-fncast9.C: New test.
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@ -16432,6 +16432,16 @@ cp_parser_decltype (cp_parser *parser)
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= parser->greater_than_is_operator_p;
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parser->greater_than_is_operator_p = true;
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/* Don't synthesize an implicit template type parameter here. This
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could happen with C++23 code like
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void f(decltype(new auto{0}));
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where we want to deduce the auto right away so that the parameter
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is of type 'int *'. */
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auto cleanup = make_temp_override
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(parser->auto_is_implicit_function_template_parm_p, false);
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/* Do not actually evaluate the expression. */
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++cp_unevaluated_operand;
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@ -24144,22 +24154,22 @@ cp_parser_type_id_1 (cp_parser *parser, cp_parser_flags flags,
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/* OK */;
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else
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{
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location_t loc = type_specifier_seq.locations[ds_type_spec];
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if (tree tmpl = CLASS_PLACEHOLDER_TEMPLATE (auto_node))
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if (!cp_parser_simulate_error (parser))
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{
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if (!cp_parser_simulate_error (parser))
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location_t loc = type_specifier_seq.locations[ds_type_spec];
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if (tree tmpl = CLASS_PLACEHOLDER_TEMPLATE (auto_node))
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{
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error_at (loc, "missing template arguments after %qT",
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auto_node);
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inform (DECL_SOURCE_LOCATION (tmpl), "%qD declared here",
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tmpl);
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}
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else if (parser->in_template_argument_list_p)
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error_at (loc, "%qT not permitted in template argument",
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auto_node);
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else
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error_at (loc, "invalid use of %qT", auto_node);
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}
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else if (parser->in_template_argument_list_p)
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error_at (loc, "%qT not permitted in template argument",
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auto_node);
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else
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error_at (loc, "invalid use of %qT", auto_node);
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return error_mark_node;
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}
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}
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@ -24668,6 +24678,15 @@ cp_parser_parameter_declaration (cp_parser *parser,
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&decl_specifiers,
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&declares_class_or_enum);
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/* [dcl.spec.auto.general]: "A placeholder-type-specifier of the form
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type-constraint opt auto can be used as a decl-specifier of the
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decl-specifier-seq of a parameter-declaration of a function declaration
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or lambda-expression..." but we must not synthesize an implicit template
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type parameter in its declarator. That is, in "void f(auto[auto{10}]);"
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we want to synthesize only the first auto. */
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auto cleanup = make_temp_override
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(parser->auto_is_implicit_function_template_parm_p, false);
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/* Complain about missing 'typename' or other invalid type names. */
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if (!decl_specifiers.any_type_specifiers_p
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&& cp_parser_parse_and_diagnose_invalid_type_name (parser))
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@ -32369,6 +32388,9 @@ cp_parser_sizeof_operand (cp_parser* parser, enum rid keyword)
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= parser->non_integral_constant_expression_p;
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parser->integral_constant_expression_p = false;
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auto cleanup = make_temp_override
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(parser->auto_is_implicit_function_template_parm_p, false);
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/* Do not actually evaluate the expression. */
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++cp_unevaluated_operand;
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++c_inhibit_evaluation_warnings;
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@ -2,6 +2,6 @@
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// { dg-do compile { target c++14 } }
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auto l4 = [](auto v, auto (&array (int)) [5]) -> int { return v + array[0]; };
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auto l5 = [](auto v, auto (&array (auto)) [5]) -> int { return v + array[0]; };
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auto l5 = [](auto v, auto (&array (auto)) [5]) -> int { return v + array[0]; }; // { dg-error ".auto. parameter not permitted in this context" }
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auto l6 = [](auto v, auto (&array (int int)) [5]) -> int { return v + array[0]; }; // { dg-error "two or more data types" }
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auto l7 = [](auto v, auto (&array (int auto)) [5]) -> int { return v + array[0]; }; // { dg-error "two or more data types" }
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@ -6,6 +6,6 @@ template<typename T> decltype(T{}) fooB(T);
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void bar()
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{
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fooA((auto*)0); // { dg-error "invalid use" }
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fooB((auto*)0); // { dg-error "invalid use" }
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fooA((auto*)0); // { dg-error "expected" }
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fooB((auto*)0); // { dg-error "expected" }
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}
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@ -3,4 +3,5 @@
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void foo();
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auto f = (auto(*)())(&foo); // { dg-error "invalid" }
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auto f = (auto(*)())(&foo); // { dg-error "expected" }
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// { dg-error "only available" "" { target c++20_down } .-1 }
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9
gcc/testsuite/g++.dg/cpp23/auto-fncast7.C
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9
gcc/testsuite/g++.dg/cpp23/auto-fncast7.C
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@ -0,0 +1,9 @@
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// PR c++/103401
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// { dg-do compile { target c++23 } }
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void f(decltype(auto(0))) { }
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int main()
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{
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f<int,int>(0); // { dg-error "no matching function" }
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}
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42
gcc/testsuite/g++.dg/cpp23/auto-fncast8.C
Normal file
42
gcc/testsuite/g++.dg/cpp23/auto-fncast8.C
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@ -0,0 +1,42 @@
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// PR c++/103401
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// { dg-do compile { target c++23 } }
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void f1 (decltype(auto(0)));
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void f2 (decltype(auto{0}));
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void f3 (int = auto(42));
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void f4 (int = auto{42});
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void f5 (decltype(auto(0)) = auto(42));
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void f6 (auto (x));
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void f7 (int[auto(10)]);
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void f8 (int[auto{10}]);
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void f9 (auto[auto{10}]);
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void f10 (auto);
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void f11 (int x, decltype(x) y);
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void f12 (int[sizeof(auto{10})]);
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void f13 (int[sizeof(auto(10))]);
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void f14 (int[__extension__ alignof(auto{10})]);
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void f15 (int[__extension__ alignof(auto(10))]);
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void
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g ()
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{
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int a[2];
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f1 (1);
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f2 (1);
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f3 ();
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f3 (1);
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f4 ();
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f4 (1);
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f5 ();
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f5 (1);
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f6 ('a');
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f7 (&a[0]);
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f8 (&a[0]);
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f9 (&a[0]);
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f10 (1);
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f11 (1, 2);
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f12 (&a[0]);
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f13 (&a[0]);
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f14 (&a[0]);
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f15 (&a[0]);
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}
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gcc/testsuite/g++.dg/cpp23/auto-fncast9.C
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17
gcc/testsuite/g++.dg/cpp23/auto-fncast9.C
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@ -0,0 +1,17 @@
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// PR c++/103401
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// { dg-do compile { target c++23 } }
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void f1(decltype(new auto{0}));
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void f2(decltype(new int{0}));
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void
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g ()
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{
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int i;
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void f3(decltype(new auto{0}));
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void f4(decltype(new int{0}));
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f1 (&i);
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f2 (&i);
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f3 (&i);
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f4 (&i);
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}
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@ -4,9 +4,9 @@
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template <typename T>
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void foo1(T& t) {
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typename T::template C<void> tcv = t;
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typename T::template C<auto> u = tcv; // { dg-error "not permitted" "" { target c++20 } }
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T::template C<auto>::f (tcv, u); // { dg-error "incomplete|not permitted" }
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(typename T::template D<auto> (t)); // { dg-error "invalid|not permitted|unable" }
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typename T::template C<auto> u = tcv; // { dg-error "" "" { target c++20 } }
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T::template C<auto>::f (tcv, u); // { dg-error "" }
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(typename T::template D<auto> (t)); // { dg-error "" }
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// { dg-warning "only available" "" { target c++17_down } .-1 }
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}
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@ -23,9 +23,9 @@ struct T1 {
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template <typename T>
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void foo2(T& t) {
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typename T::template C<void> tcv = t;
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typename T::template C<auto> u = tcv; // { dg-error "not permitted" "" { target c++20 } }
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T::template C<auto>::f (tcv, u); // { dg-error "incomplete|not permitted" }
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T::template D<auto> (t); // { dg-error "invalid|not permitted" }
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typename T::template C<auto> u = tcv; // { dg-error "" "" { target c++20 } }
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T::template C<auto>::f (tcv, u); // { dg-error "" }
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T::template D<auto> (t); // { dg-error "" }
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}
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struct T2 {
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@ -8,9 +8,9 @@
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template <typename T>
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void foo1(T& t) {
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typename T::template C<void> tcv = t;
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typename T::template C<auto> u = tcv; // { dg-error "not permitted" "" { target c++20 } }
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T::template C<auto>::f (tcv, u); // { dg-error "incomplete|not permitted" }
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(typename T::template D<auto> (t)); // { dg-error "invalid|not permitted|no class" }
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typename T::template C<auto> u = tcv; // { dg-error "" "" { target c++20 } }
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T::template C<auto>::f (tcv, u); // { dg-error "" }
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(typename T::template D<auto> (t)); // { dg-error "" }
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// { dg-warning "only available" "" { target c++17_down } .-1 }
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}
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@ -27,9 +27,9 @@ struct T1 {
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template <typename T>
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void foo2(T& t) {
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typename T::template C<void> tcv = t;
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typename T::template C<auto> u = tcv; // { dg-error "not permitted" "" { target c++20 } }
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T::template C<auto>::f (tcv, u); // { dg-error "incomplete|not permitted" }
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T::template D<auto> (t); // { dg-error "yields a type|not permitted" }
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typename T::template C<auto> u = tcv; // { dg-error "" "" { target c++20 } }
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T::template C<auto>::f (tcv, u); // { dg-error "" }
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T::template D<auto> (t); // { dg-error "" }
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}
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struct T2 {
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@ -5,5 +5,5 @@ template<typename> void foo() {}
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void bar()
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{
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foo<auto>(); // { dg-error "not permitted|invalid|no matching function" }
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foo<auto>(); // { dg-error "" }
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}
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