OK.
On Mon, May 21, 2018 at 3:50 PM, Marek Polacek <pola...@redhat.com> wrote:
> This is my attempt to implement P0614R1, a C++20 feature whereby we may now
> use
> an init-statement in a range-based for loop like this:
>
> for (int i = bar (); const auto &x : a)
> // ...
>
> The somewhat tricky part was to distinguish a range-based for from an
> ordinary for
> statement, hence the cp_parser_range_based_for_with_init_p shenanigans. Note
> that we must be able to cope with lambdas/statement-expressions in the
> initializer as well as with loops such as
>
> for (int i = 0; int j = 0; )
> // ...
>
> and the following seems to handle all of it.
>
> What d'ya think?
>
> Bootstrapped/regtested on x86_64-linux, ok for trunk?
>
> 2018-05-21 Marek Polacek <pola...@redhat.com>
>
> Implement P0614R1, Range-based for statements with initializer.
> * parser.c (cp_parser_range_based_for_with_init_p): New.
> (cp_parser_init_statement): Use it. Parse the optional init-statement
> for a range-based for loop.
>
> * g++.dg/cpp2a/range-for1.C: New test.
> * g++.dg/cpp2a/range-for2.C: New test.
> * g++.dg/cpp2a/range-for3.C: New test.
> * g++.dg/cpp2a/range-for4.C: New test.
> * g++.dg/cpp2a/range-for5.C: New test.
> * g++.dg/cpp2a/range-for6.C: New test.
>
> diff --git gcc/cp/parser.c gcc/cp/parser.c
> index c0058085ee9..47a825f2da0 100644
> --- gcc/cp/parser.c
> +++ gcc/cp/parser.c
> @@ -11255,6 +11255,39 @@ cp_parser_statement_seq_opt (cp_parser* parser, tree
> in_statement_expr)
> }
> }
>
> +/* Return true if this is the C++20 version of range-based-for with
> + init-statement. */
> +
> +static bool
> +cp_parser_range_based_for_with_init_p (cp_parser *parser)
> +{
> + bool r = false;
> +
> + /* Save tokens so that we can put them back. */
> + cp_lexer_save_tokens (parser->lexer);
> +
> + /* There has to be an unnested ; followed by an unnested :. */
> + if (cp_parser_skip_to_closing_parenthesis_1 (parser,
> + /*recovering=*/false,
> + CPP_SEMICOLON,
> + /*consume_paren=*/false) != -1)
> + goto out;
> +
> + /* We found the semicolon, eat it now. */
> + cp_lexer_consume_token (parser->lexer);
> + /* Now look for ':' that is not nested in () or {}. */
> + r = (cp_parser_skip_to_closing_parenthesis_1 (parser,
> + /*recovering=*/false,
> + CPP_COLON,
> + /*consume_paren=*/false) ==
> -1);
> +
> +out:
> + /* Roll back the tokens we skipped. */
> + cp_lexer_rollback_tokens (parser->lexer);
> +
> + return r;
> +}
> +
> /* Return true if we're looking at (init; cond), false otherwise. */
>
> static bool
> @@ -12242,7 +12275,7 @@ cp_parser_iteration_statement (cp_parser* parser,
> bool *if_p, bool ivdep,
> simple-declaration */
>
> static bool
> -cp_parser_init_statement (cp_parser* parser, tree *decl)
> +cp_parser_init_statement (cp_parser *parser, tree *decl)
> {
> /* If the next token is a `;', then we have an empty
> expression-statement. Grammatically, this is also a
> @@ -12255,6 +12288,29 @@ cp_parser_init_statement (cp_parser* parser, tree
> *decl)
> bool is_range_for = false;
> bool saved_colon_corrects_to_scope_p =
> parser->colon_corrects_to_scope_p;
>
> + /* Try to parse the init-statement. */
> + if (cp_parser_range_based_for_with_init_p (parser))
> + {
> + 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_parser_parse_definitely (parser))
> + /* That didn't work, try to parse it as an expression-statement.
> */
> + cp_parser_expression_statement (parser, NULL_TREE);
> +
> + if (cxx_dialect < cxx2a)
> + {
> + pedwarn (cp_lexer_peek_token (parser->lexer)->location, 0,
> + "range-based %<for%> loops with initializer only "
> + "available with -std=c++2a or -std=gnu++2a");
> + *decl = error_mark_node;
> + }
> + }
> +
> /* A colon is used in range-based for. */
> parser->colon_corrects_to_scope_p = false;
>
> @@ -12268,7 +12324,7 @@ cp_parser_init_statement (cp_parser* parser, tree
> *decl)
> parser->colon_corrects_to_scope_p = saved_colon_corrects_to_scope_p;
> if (cp_lexer_next_token_is (parser->lexer, CPP_COLON))
> {
> - /* It is a range-for, consume the ':' */
> + /* It is a range-for, consume the ':'. */
> cp_lexer_consume_token (parser->lexer);
> is_range_for = true;
> if (cxx_dialect < cxx11)
> @@ -12280,9 +12336,9 @@ cp_parser_init_statement (cp_parser* parser, tree
> *decl)
> }
> }
> else
> - /* The ';' is not consumed yet because we told
> - cp_parser_simple_declaration not to. */
> - cp_parser_require (parser, CPP_SEMICOLON, RT_SEMICOLON);
> + /* The ';' is not consumed yet because we told
> + cp_parser_simple_declaration not to. */
> + cp_parser_require (parser, CPP_SEMICOLON, RT_SEMICOLON);
>
> if (cp_parser_parse_definitely (parser))
> return is_range_for;
> diff --git gcc/testsuite/g++.dg/cpp2a/range-for1.C
> gcc/testsuite/g++.dg/cpp2a/range-for1.C
> index e69de29bb2d..3a5523585a1 100644
> --- gcc/testsuite/g++.dg/cpp2a/range-for1.C
> +++ gcc/testsuite/g++.dg/cpp2a/range-for1.C
> @@ -0,0 +1,16 @@
> +// P0614R1
> +// { dg-do compile { target c++11 } }
> +// { dg-options "" }
> +
> +void
> +fn1 ()
> +{
> + int a[] = { 1, 2, 3, 4, 5 };
> +
> + for (int i = 0; auto x : a) // { dg-warning "range-based .for. loops with
> initializer only available with" "" { target c++17_down } }
> + ++i;
> +
> + int i;
> + for (i = 0; auto x : a) // { dg-warning "range-based .for. loops with
> initializer only available with" "" { target c++17_down } }
> + ++i;
> +}
> diff --git gcc/testsuite/g++.dg/cpp2a/range-for2.C
> gcc/testsuite/g++.dg/cpp2a/range-for2.C
> index e69de29bb2d..acb16c57d1c 100644
> --- gcc/testsuite/g++.dg/cpp2a/range-for2.C
> +++ gcc/testsuite/g++.dg/cpp2a/range-for2.C
> @@ -0,0 +1,16 @@
> +// P0614R1
> +// { dg-do compile }
> +// { dg-options "-std=c++2a" }
> +
> +void
> +fn1 ()
> +{
> + int a[] = { 1, 2, 3, 4, 5 };
> +
> + for (int i = 0; auto x : a)
> + ++i;
> +
> + int i;
> + for (i = 0; auto x : a)
> + ++i;
> +}
> diff --git gcc/testsuite/g++.dg/cpp2a/range-for3.C
> gcc/testsuite/g++.dg/cpp2a/range-for3.C
> index e69de29bb2d..291e605b92f 100644
> --- gcc/testsuite/g++.dg/cpp2a/range-for3.C
> +++ gcc/testsuite/g++.dg/cpp2a/range-for3.C
> @@ -0,0 +1,26 @@
> +// P0614R1
> +// { dg-do compile }
> +// { dg-options "-std=c++2a" }
> +
> +static const int a[] = { 1, 2, 3, 4, 5 };
> +extern void foo (int);
> +extern void bar (int, int);
> +
> +constexpr int
> +baz ()
> +{
> + return 6;
> +}
> +
> +void
> +fn1 (int i)
> +{
> + for ((i += 2); auto x : a)
> + foo (i);
> +
> + for (auto j = 0, k = 0; auto x : a)
> + bar (j + k, x);
> +
> + for (constexpr int j = baz (); auto x : a)
> + bar (x, j);
> +}
> diff --git gcc/testsuite/g++.dg/cpp2a/range-for4.C
> gcc/testsuite/g++.dg/cpp2a/range-for4.C
> index e69de29bb2d..6ba783f46cb 100644
> --- gcc/testsuite/g++.dg/cpp2a/range-for4.C
> +++ gcc/testsuite/g++.dg/cpp2a/range-for4.C
> @@ -0,0 +1,27 @@
> +// P0614R1
> +// { dg-do run }
> +// { dg-options "-std=c++2a" }
> +
> +int
> +main ()
> +{
> + int a[] = { 1, 2, 3, 4, 5 };
> +
> + for (int i = 1; auto x : a)
> + if (i++ != x)
> + __builtin_abort ();
> +
> + int i;
> + for (i = 1; auto x : a)
> + if (i++ != x)
> + __builtin_abort ();
> +
> + i = 0;
> + for (i++; auto x : a)
> + if (i != 1)
> + __builtin_abort ();
> +
> + for (int s[] = { 1, 1, 1 }; auto x : s)
> + if (x != 1)
> + __builtin_abort ();
> +}
> diff --git gcc/testsuite/g++.dg/cpp2a/range-for5.C
> gcc/testsuite/g++.dg/cpp2a/range-for5.C
> index e69de29bb2d..62f1c2f04e1 100644
> --- gcc/testsuite/g++.dg/cpp2a/range-for5.C
> +++ gcc/testsuite/g++.dg/cpp2a/range-for5.C
> @@ -0,0 +1,46 @@
> +// P0614R1
> +// { dg-do compile }
> +// { dg-options "-std=c++2a" }
> +
> +void
> +fn1 ()
> +{
> + int a[] = { 1, 2, 3, 4, 5 };
> +
> + for (int i = 0; auto x : a)
> + ++i;
> +
> + i = 0; // { dg-error "not declared" }
> +
> + for (int i = 0; auto x : a)
> + {
> + for (int j = 0; auto x : a)
> + {
> + for (int k = 0; auto x : a)
> + k++;
> + k++; // { dg-error "not declared" }
> + }
> + j++; // { dg-error "not declared" }
> + }
> +}
> +
> +void
> +fn2 ()
> +{
> + int a[] = { 1, 2, 3, 4, 5 };
> + for (int i = 0; auto x : a)
> + int i = 3; // { dg-error "redeclaration" }
> +}
> +void
> +fn3 ()
> +{
> + int a[] = { 1, 2, 3, 4, 5 };
> +
> + for (;:) // { dg-error "expected" }
> + {
> + }
> +
> + for (;;:) // { dg-error "expected" }
> + {
> + }
> +}
> diff --git gcc/testsuite/g++.dg/cpp2a/range-for6.C
> gcc/testsuite/g++.dg/cpp2a/range-for6.C
> index e69de29bb2d..4cee60a839e 100644
> --- gcc/testsuite/g++.dg/cpp2a/range-for6.C
> +++ gcc/testsuite/g++.dg/cpp2a/range-for6.C
> @@ -0,0 +1,17 @@
> +// P0614R1
> +// { dg-do run }
> +// { dg-options "-std=c++2a" }
> +
> +int
> +main ()
> +{
> + int a[] = { 1, 2, 3, 4, 5 };
> +
> + for (int i = []{ return 3; }(); auto x : a)
> + if (i != 3)
> + __builtin_abort ();
> +
> + for (int i = ({ 3; }); auto x : a)
> + if (i != 3)
> + __builtin_abort ();
> +}
