The following patch implements C++23 P2360R0. This proposal merely extends init-statement to contain alias-declaration. init-statement is used in if/for/switch. The unsightly duplication of the new code seems to be necessary to handle
for ( init-statement condition[opt] ; expression[opt] ) statement as well as for ( init-statement[opt] for-range-declaration : for-range-initializer ) statement Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk? PR c++/102617 gcc/cp/ChangeLog: * parser.c (cp_parser_init_statement): Allow alias-declaration in init-statement. gcc/testsuite/ChangeLog: * g++.dg/cpp23/init-stmt1.C: New test. * g++.dg/cpp23/init-stmt2.C: New test. --- gcc/cp/parser.c | 52 +++++++++++++++++++------ gcc/testsuite/g++.dg/cpp23/init-stmt1.C | 31 +++++++++++++++ gcc/testsuite/g++.dg/cpp23/init-stmt2.C | 25 ++++++++++++ 3 files changed, 96 insertions(+), 12 deletions(-) create mode 100644 gcc/testsuite/g++.dg/cpp23/init-stmt1.C create mode 100644 gcc/testsuite/g++.dg/cpp23/init-stmt2.C diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c index 49d951cfb19..8ba5370740e 100644 --- a/gcc/cp/parser.c +++ b/gcc/cp/parser.c @@ -12040,6 +12040,7 @@ cp_parser_handle_directive_omp_attributes (cp_parser *parser, tree *pattrs, init-statement: expression-statement simple-declaration + alias-declaration TM Extension: @@ -13987,12 +13988,13 @@ cp_parser_iteration_statement (cp_parser* parser, bool *if_p, bool ivdep, return statement; } -/* Parse a init-statement or the declarator of a range-based-for. +/* Parse an init-statement or the declarator of a range-based-for. Returns true if a range-based-for declaration is seen. init-statement: expression-statement - simple-declaration */ + simple-declaration + alias-declaration */ static bool cp_parser_init_statement (cp_parser *parser, tree *decl) @@ -14013,11 +14015,24 @@ cp_parser_init_statement (cp_parser *parser, tree *decl) { tree dummy; cp_parser_parse_tentatively (parser); - /* Parse the declaration. */ - cp_parser_simple_declaration (parser, - /*function_definition_allowed_p=*/false, - &dummy); - cp_parser_require (parser, CPP_SEMICOLON, RT_SEMICOLON); + if (cp_lexer_next_token_is_keyword (parser->lexer, RID_USING)) + { + cp_parser_alias_declaration (parser); + if (cxx_dialect < cxx23 + && !cp_parser_uncommitted_to_tentative_parse_p (parser)) + pedwarn (cp_lexer_peek_token (parser->lexer)->location, + OPT_Wc__23_extensions, + "alias-declaration in init-statement only " + "available with %<-std=c++23%> or %<-std=gnu++23%>"); + } + else + { + /* Parse the declaration. */ + cp_parser_simple_declaration (parser, + /*function_definition_allowed_p=*/ + false, &dummy); + cp_parser_require (parser, CPP_SEMICOLON, RT_SEMICOLON); + } if (!cp_parser_parse_definitely (parser)) /* That didn't work, try to parse it as an expression-statement. */ cp_parser_expression_statement (parser, NULL_TREE); @@ -14038,10 +14053,23 @@ cp_parser_init_statement (cp_parser *parser, tree *decl) /* We're going to speculatively look for a declaration, falling back to an expression, if necessary. */ cp_parser_parse_tentatively (parser); - /* Parse the declaration. */ - cp_parser_simple_declaration (parser, - /*function_definition_allowed_p=*/false, - decl); + bool expect_semicolon_p = true; + if (cp_lexer_next_token_is_keyword (parser->lexer, RID_USING)) + { + cp_parser_alias_declaration (parser); + expect_semicolon_p = false; + if (cxx_dialect < cxx23 + && !cp_parser_uncommitted_to_tentative_parse_p (parser)) + pedwarn (cp_lexer_peek_token (parser->lexer)->location, + OPT_Wc__23_extensions, + "alias-declaration in init-statement only " + "available with %<-std=c++23%> or %<-std=gnu++23%>"); + } + else + /* Parse the declaration. */ + cp_parser_simple_declaration (parser, + /*function_definition_allowed_p=*/false, + decl); parser->colon_corrects_to_scope_p = saved_colon_corrects_to_scope_p; if (cp_lexer_next_token_is (parser->lexer, CPP_COLON)) { @@ -14054,7 +14082,7 @@ cp_parser_init_statement (cp_parser *parser, tree *decl) "range-based %<for%> loops only available with " "%<-std=c++11%> or %<-std=gnu++11%>"); } - else + else if (expect_semicolon_p) /* The ';' is not consumed yet because we told cp_parser_simple_declaration not to. */ cp_parser_require (parser, CPP_SEMICOLON, RT_SEMICOLON); diff --git a/gcc/testsuite/g++.dg/cpp23/init-stmt1.C b/gcc/testsuite/g++.dg/cpp23/init-stmt1.C new file mode 100644 index 00000000000..29e3256aae6 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp23/init-stmt1.C @@ -0,0 +1,31 @@ +// PR c++/102617 +// P2360R0: Extend init-statement to allow alias-declaration +// { dg-do compile { target c++20 } } +// Test valid use. + +int v[10]; + +void +g () +{ + for (using T = int; (T) false;) // { dg-error "only available with" "" { target c++20_only } } + ; + for (using T = int; T e : v) // { dg-error "only available with" "" { target c++20_only } } + (void) e; + if (using T = int; true) // { dg-error "only available with" "" { target c++20_only } } + { + T x = 0; + (void) x; + } + if constexpr (using T = int; true) // { dg-error "only available with" "" { target c++20_only } } + { + T x = 0; + (void) x; + } + switch (using T = int; 42) // { dg-error "only available with" "" { target c++20_only } } + case 42: + { + T x = 0; + (void) x; + } +} diff --git a/gcc/testsuite/g++.dg/cpp23/init-stmt2.C b/gcc/testsuite/g++.dg/cpp23/init-stmt2.C new file mode 100644 index 00000000000..ca6201bc340 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp23/init-stmt2.C @@ -0,0 +1,25 @@ +// PR c++/102617 +// P2360R0: Extend init-statement to allow alias-declaration +// { dg-do compile { target c++23 } } +// Test invalid use. + +int v[10]; +namespace N { using X = int; } + +void +g () +{ + for (using N::X; false;) // { dg-error "expected" } + ; + for (using N::X; int e : v) // { dg-error "expected" } + (void) e; + for (using T = int; using U = int; int e : v) // { dg-error "" } + ; + if (using N::X; false) // { dg-error "expected" } + {} + switch (using N::X; 0) // { dg-error "expected" } + ; + if (using T = int;) // { dg-error "expected" } + { + } +} base-commit: 1373066a46d8d47abd97e46a005aef3b3dbfe94a -- 2.31.1