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c++: Implement P2662R3, Pack Indexing [PR113798]

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This patch implements C++26 Pack Indexing, as described in
<https://wg21.link/P2662R3>.

The issue discussing how to mangle pack indexes has not been resolved
yet <https://github.com/itanium-cxx-abi/cxx-abi/issues/175> and I've
made no attempt to address it so far.

Unlike v1, which used augmented TYPE/EXPR_PACK_EXPANSION codes, this
version introduces two new codes: PACK_INDEX_EXPR and PACK_INDEX_TYPE.
Both carry two operands: the pack expansion and the index.  They are
handled in tsubst_pack_index: substitute the index and the pack and
then extract the element from the vector (if possible).

To handle pack indexing in a decltype or with decltype(auto), there is
also the new PACK_INDEX_PARENTHESIZED_P flag.

With this feature, it's valid to write something like

  using U = tmpl<Ts...[Is]...>;

where we first expand the template argument into

  Ts...[Is#0], Ts...[Is#1], ...

and then substitute each individual pack index.

	PR c++/113798

gcc/cp/ChangeLog:

	* constexpr.cc (potential_constant_expression_1) <case PACK_INDEX_EXPR>:
	New case.
	* cp-objcp-common.cc (cp_common_init_ts): Mark PACK_INDEX_TYPE and
	PACK_INDEX_EXPR.
	* cp-tree.def (PACK_INDEX_TYPE): New.
	(PACK_INDEX_EXPR): New.
	* cp-tree.h (WILDCARD_TYPE_P): Also check PACK_INDEX_TYPE.
	(PACK_INDEX_CHECK): Define.
	(PACK_INDEX_P): Define.
	(PACK_INDEX_PACK): Define.
	(PACK_INDEX_INDEX): Define.
	(PACK_INDEX_PARENTHESIZED_P): Define.
	(make_pack_index): Declare.
	(pack_index_element): Declare.
	* cxx-pretty-print.cc (cxx_pretty_printer::expression) <case
	PACK_INDEX_EXPR>: New case.
	(cxx_pretty_printer::type_id) <case PACK_INDEX_TYPE>: New case.
	* error.cc (dump_type) <case PACK_INDEX_TYPE>: New case.
	(dump_type_prefix): Handle PACK_INDEX_TYPE.
	(dump_type_suffix): Likewise.
	(dump_expr) <case PACK_INDEX_EXPR>: New case.
	* mangle.cc (write_type) <case PACK_INDEX_TYPE>: New case.
	* module.cc (trees_out::type_node) <case PACK_INDEX_TYPE>: New case.
	(trees_in::tree_node) <case PACK_INDEX_TYPE>: New case.
	* parser.cc (cp_parser_next_tokens_are_pack_index_p): New.
	(cp_parser_pack_index): New.
	(cp_parser_primary_expression): Handle a C++26 pack-index-expression.
	(cp_parser_unqualified_id): Handle a C++26 pack-index-specifier.
	(cp_parser_nested_name_specifier_opt): See if a pack-index-specifier
	follows.
	(cp_parser_qualifying_entity): Handle a C++26 pack-index-specifier.
	(cp_parser_decltype_expr): Set id_expression_or_member_access_p for
	pack indexing.
	(cp_parser_mem_initializer_id): Handle a C++26 pack-index-specifier.
	(cp_parser_simple_type_specifier): Likewise.
	(cp_parser_base_specifier): Likewise.
	* pt.cc (iterative_hash_template_arg) <case PACK_INDEX_TYPE,
	PACK_INDEX_EXPR>: New case.
	(find_parameter_packs_r) <case PACK_INDEX_TYPE, PACK_INDEX_EXPR>: New
	case.
	(make_pack_index): New.
	(tsubst_pack_index): New.
	(tsubst): Avoid tsubst on PACK_INDEX_TYPE.
	<case TYPENAME_TYPE>: Add a call to error.
	<case PACK_INDEX_TYPE>: New case.
	(tsubst_expr) <case PACK_INDEX_EXPR>: New case.
	(dependent_type_p_r): Return true for PACK_INDEX_TYPE.
	(type_dependent_expression_p): Recurse on PACK_INDEX_PACK for
	PACK_INDEX_EXPR.
	* ptree.cc (cxx_print_type) <case PACK_INDEX_TYPE>: New case.
	* semantics.cc (finish_parenthesized_expr): Set
	PACK_INDEX_PARENTHESIZED_P for PACK_INDEX_EXPR.
	(finish_type_pack_element): Adjust error messages.
	(pack_index_element): New.
	* tree.cc (cp_tree_equal) <case PACK_INDEX_EXPR>: New case.
	(cp_walk_subtrees) <case PACK_INDEX_TYPE, PACK_INDEX_EXPR>: New case.
	* typeck.cc (structural_comptypes) <case PACK_INDEX_TYPE>: New case.

libstdc++-v3/ChangeLog:

	* testsuite/20_util/tuple/element_access/get_neg.cc: Adjust
	dg-prune-output.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp26/pack-indexing1.C: New test.
	* g++.dg/cpp26/pack-indexing2.C: New test.
	* g++.dg/cpp26/pack-indexing3.C: New test.
	* g++.dg/cpp26/pack-indexing4.C: New test.
	* g++.dg/cpp26/pack-indexing5.C: New test.
	* g++.dg/cpp26/pack-indexing6.C: New test.
	* g++.dg/cpp26/pack-indexing7.C: New test.
	* g++.dg/cpp26/pack-indexing8.C: New test.
	* g++.dg/cpp26/pack-indexing9.C: New test.
	* g++.dg/cpp26/pack-indexing10.C: New test.
	* g++.dg/cpp26/pack-indexing11.C: New test.
	* g++.dg/modules/pack-index-1_a.C: New test.
	* g++.dg/modules/pack-index-1_b.C: New test.
This commit is contained in:
Marek Polacek 2024-10-09 11:54:37 -04:00
parent c5126f0a00
commit c435272166
28 changed files with 910 additions and 38 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

3
gcc/cp/constexpr.cc
View file

@ -9943,6 +9943,9 @@ potential_constant_expression_1 (tree t, bool want_rval, bool strict, bool now,
case EXPR_PACK_EXPANSION:
return RECUR (PACK_EXPANSION_PATTERN (t), want_rval);
case PACK_INDEX_EXPR:
return true;
case INDIRECT_REF:
{
tree x = TREE_OPERAND (t, 0);

2
gcc/cp/cp-objcp-common.cc
View file

@ -645,6 +645,7 @@ cp_common_init_ts (void)
MARK_TS_TYPE_NON_COMMON (TEMPLATE_TEMPLATE_PARM);
MARK_TS_TYPE_NON_COMMON (TEMPLATE_TYPE_PARM);
MARK_TS_TYPE_NON_COMMON (TYPE_PACK_EXPANSION);
MARK_TS_TYPE_NON_COMMON (PACK_INDEX_TYPE);
/* Statements. */
MARK_TS_EXP (CLEANUP_STMT);
@ -702,6 +703,7 @@ cp_common_init_ts (void)
MARK_TS_EXP (NONTYPE_ARGUMENT_PACK);
MARK_TS_EXP (UNARY_LEFT_FOLD_EXPR);
MARK_TS_EXP (UNARY_RIGHT_FOLD_EXPR);
MARK_TS_EXP (PACK_INDEX_EXPR);
/* Constraints. */
MARK_TS_EXP (COMPOUND_REQ);

8
gcc/cp/cp-tree.def
View file

@ -397,6 +397,14 @@ DEFTREECODE (TYPE_PACK_EXPANSION, "type_pack_expansion", tcc_type, 0)
but will be used for expressions. */
DEFTREECODE (EXPR_PACK_EXPANSION, "expr_pack_expansion", tcc_expression, 3)
/* Represents a pack index Ts...[I], yielding a type. PACK_INDEX_PACK is
the pack expansion Ts, PACK_INDEX_INDEX the index I. */
DEFTREECODE (PACK_INDEX_TYPE, "pack_index_type", tcc_type, 0)
/* Represents a pack index Ts...[I], yielding an expression. PACK_INDEX_PACK
is the pack expansion Ts, PACK_INDEX_INDEX the index I. */
DEFTREECODE (PACK_INDEX_EXPR, "pack_index_expr", tcc_expression, 2)
/* Selects the Ith parameter out of an argument pack. This node will
be used when instantiating pack expansions; see
tsubst_pack_expansion.

31
gcc/cp/cp-tree.h
View file

@ -451,6 +451,7 @@ extern GTY(()) tree cp_global_trees[CPTI_MAX];
ATOMIC_CONSTR_MAP_INSTANTIATED_P (in ATOMIC_CONSTR)
contract_semantic (in ASSERTION_, PRECONDITION_, POSTCONDITION_STMT)
RETURN_EXPR_LOCAL_ADDR_P (in RETURN_EXPR)
PACK_INDEX_PARENTHESIZED_P (in PACK_INDEX_*)
1: IDENTIFIER_KIND_BIT_1 (in IDENTIFIER_NODE)
TI_PENDING_TEMPLATE_FLAG.
TEMPLATE_PARMS_FOR_INLINE.
@ -2258,7 +2259,8 @@ enum languages { lang_c, lang_cplusplus };
|| TREE_CODE (T) == BOUND_TEMPLATE_TEMPLATE_PARM \
|| TREE_CODE (T) == DECLTYPE_TYPE \
|| TREE_CODE (T) == TRAIT_TYPE \
|| TREE_CODE (T) == DEPENDENT_OPERATOR_TYPE)
|| TREE_CODE (T) == DEPENDENT_OPERATOR_TYPE \
|| TREE_CODE (T) == PACK_INDEX_TYPE)
/* Nonzero if T is a class (or struct or union) type. Also nonzero
for template type parameters, typename types, and instantiated
@ -4001,6 +4003,9 @@ struct GTY(()) lang_decl {
#define PACK_EXPANSION_CHECK(NODE) \
TREE_CHECK2 (NODE, TYPE_PACK_EXPANSION, EXPR_PACK_EXPANSION)
#define PACK_INDEX_CHECK(NODE) \
TREE_CHECK2 (NODE, PACK_INDEX_TYPE, PACK_INDEX_EXPR)
/* Extracts the type or expression pattern from a TYPE_PACK_EXPANSION or
EXPR_PACK_EXPANSION. */
#define PACK_EXPANSION_PATTERN(NODE) \
@ -4025,6 +4030,22 @@ struct GTY(()) lang_decl {
? &TYPE_MAX_VALUE_RAW (NODE) \
: &TREE_OPERAND ((NODE), 2))
/* True if NODE is a pack index. */
#define PACK_INDEX_P(NODE) \
(TREE_CODE (NODE) == PACK_INDEX_TYPE \
|| TREE_CODE (NODE) == PACK_INDEX_EXPR)
/* For a pack index T...[N], the pack expansion 'T...'. */
#define PACK_INDEX_PACK(NODE) \
(TREE_CODE (PACK_INDEX_CHECK (NODE)) == PACK_INDEX_TYPE \
? TREE_TYPE (NODE) : TREE_OPERAND (NODE, 0))
/* For a pack index T...[N], the index N. */
#define PACK_INDEX_INDEX(NODE) \
*(TREE_CODE (PACK_INDEX_CHECK (NODE)) == PACK_INDEX_TYPE \
? &TYPE_MAX_VALUE_RAW (NODE) \
: &TREE_OPERAND ((NODE), 1))
/* True iff this pack expansion is within a function context. */
#define PACK_EXPANSION_LOCAL_P(NODE) \
TREE_LANG_FLAG_0 (PACK_EXPANSION_CHECK (NODE))
@ -4042,6 +4063,11 @@ struct GTY(()) lang_decl {
#define PACK_EXPANSION_FORCE_EXTRA_ARGS_P(NODE) \
TREE_LANG_FLAG_3 (PACK_EXPANSION_CHECK (NODE))
/* Indicates whether a pack expansion has been parenthesized. Used for
a pack expansion in a decltype. */
#define PACK_INDEX_PARENTHESIZED_P(NODE) \
TREE_LANG_FLAG_1 (TREE_CHECK (NODE, PACK_INDEX_EXPR))
/* True iff the wildcard can match a template parameter pack. */
#define WILDCARD_PACK_P(NODE) TREE_LANG_FLAG_0 (NODE)
@ -7582,6 +7608,7 @@ extern bool template_parameter_pack_p (const_tree);
extern bool function_parameter_pack_p (const_tree);
extern bool function_parameter_expanded_from_pack_p (tree, tree);
extern tree make_pack_expansion (tree, tsubst_flags_t = tf_warning_or_error);
extern tree make_pack_index (tree, tree);
extern bool check_for_bare_parameter_packs (tree, location_t = UNKNOWN_LOCATION);
extern tree build_template_info (tree, tree);
extern tree get_template_info (const_tree);
@ -7907,6 +7934,8 @@ extern tree finish_underlying_type (tree);
extern tree calculate_bases (tree, tsubst_flags_t);
extern tree finish_bases (tree, bool);
extern tree calculate_direct_bases (tree, tsubst_flags_t);
extern tree pack_index_element (tree, tree, bool,
tsubst_flags_t);
extern tree finish_offsetof (tree, tree, location_t);
extern void finish_decl_cleanup (tree, tree);
extern void finish_eh_cleanup (tree);

14
gcc/cp/cxx-pretty-print.cc
View file

@ -1219,6 +1219,13 @@ cxx_pretty_printer::expression (tree t)
pp_cxx_ws_string (this, "...");
break;
case PACK_INDEX_EXPR:
expression (PACK_INDEX_PACK (t));
pp_cxx_left_bracket (this);
expression (PACK_INDEX_INDEX (t));
pp_cxx_right_bracket (this);
break;
case UNARY_LEFT_FOLD_EXPR:
pp_cxx_unary_left_fold_expression (this, t);
break;
@ -1919,6 +1926,13 @@ cxx_pretty_printer::type_id (tree t)
pp_cxx_ws_string (this, "...");
break;
case PACK_INDEX_TYPE:
type_id (PACK_INDEX_PACK (t));
pp_cxx_left_bracket (this);
expression (PACK_INDEX_INDEX (t));
pp_cxx_right_bracket (this);
break;
case TYPE_ARGUMENT_PACK:
{
tree args = ARGUMENT_PACK_ARGS (t);

16
gcc/cp/error.cc
View file

@ -813,6 +813,13 @@ dump_type (cxx_pretty_printer *pp, tree t, int flags)
pp_cxx_ws_string (pp, "...");
break;
case PACK_INDEX_TYPE:
dump_type (pp, PACK_INDEX_PACK (t), flags);
pp_cxx_left_bracket (pp);
dump_expr (pp, PACK_INDEX_INDEX (t), flags & ~TFF_EXPR_IN_PARENS);
pp_cxx_right_bracket (pp);
break;
case TYPE_ARGUMENT_PACK:
dump_template_argument (pp, t, flags);
break;
@ -1087,6 +1094,7 @@ dump_type_prefix (cxx_pretty_printer *pp, tree t, int flags)
case TYPE_PACK_EXPANSION:
case FIXED_POINT_TYPE:
case NULLPTR_TYPE:
case PACK_INDEX_TYPE:
dump_type (pp, t, flags);
pp->set_padding (pp_before);
break;
@ -1219,6 +1227,7 @@ dump_type_suffix (cxx_pretty_printer *pp, tree t, int flags)
case TYPE_PACK_EXPANSION:
case FIXED_POINT_TYPE:
case NULLPTR_TYPE:
case PACK_INDEX_TYPE:
break;
default:
@ -3102,6 +3111,13 @@ dump_expr (cxx_pretty_printer *pp, tree t, int flags)
pp->expression (t);
break;
case PACK_INDEX_EXPR:
pp->expression (PACK_INDEX_PACK (t));
pp_cxx_left_bracket (pp);
pp->expression (PACK_INDEX_INDEX (t));
pp_cxx_right_bracket (pp);
break;
case TRUTH_AND_EXPR:
case TRUTH_OR_EXPR:
case TRUTH_XOR_EXPR:

6
gcc/cp/mangle.cc
View file

@ -2668,6 +2668,12 @@ write_type (tree type)
"use library traits instead", type);
break;
case PACK_INDEX_TYPE:
/* TODO Mangle pack indexing
<https://github.com/itanium-cxx-abi/cxx-abi/issues/175>. */
sorry ("mangling type pack index");
break;
case LANG_TYPE:
/* fall through. */

14
gcc/cp/module.cc
View file

@ -9273,6 +9273,11 @@ trees_out::type_node (tree type)
tree_node (PACK_EXPANSION_EXTRA_ARGS (type));
break;
case PACK_INDEX_TYPE:
tree_node (PACK_INDEX_PACK (type));
tree_node (PACK_INDEX_INDEX (type));
break;
case TYPENAME_TYPE:
{
tree_node (TYPE_CONTEXT (type));
@ -9840,6 +9845,15 @@ trees_in::tree_node (bool is_use)
}
break;
case PACK_INDEX_TYPE:
{
tree pack = tree_node ();
tree index = tree_node ();
if (!get_overrun ())
res = make_pack_index (pack, index);
}
break;
case TYPENAME_TYPE:
{
tree ctx = tree_node ();

167
gcc/cp/parser.cc
View file

@ -5740,6 +5740,62 @@ cp_parser_fold_expression (cp_parser *parser, tree expr1)
return finish_binary_fold_expr (loc, expr1, expr2, op);
}
/* Return true iff the next tokens (following a typedef-name or id-expression)
start a pack index. */
static bool
cp_parser_next_tokens_are_pack_index_p (cp_parser *parser)
{
return (cp_lexer_next_token_is (parser->lexer, CPP_ELLIPSIS)
&& cp_lexer_nth_token_is (parser->lexer, 2, CPP_OPEN_SQUARE));
}
/* Parse a pack-index-specifier:
pack-index-specifier:
typedef-name ... [ constant-expression ]
or a pack-index-expression:
pack-index-expression:
id-expression ... [ constant-expression ]
PACK is the parsed typedef-name or the id-expression. Returns either
a PACK_INDEX_TYPE or PACK_INDEX_EXPR. */
static tree
cp_parser_pack_index (cp_parser *parser, tree pack)
{
if (cxx_dialect < cxx26)
pedwarn (cp_lexer_peek_token (parser->lexer)->location,
OPT_Wc__26_extensions, "pack indexing only available with "
"%<-std=c++2c%> or %<-std=gnu++2c%>");
/* Consume the '...' token. */
cp_lexer_consume_token (parser->lexer);
/* Consume the '['. */
cp_lexer_consume_token (parser->lexer);
if (cp_lexer_next_token_is (parser->lexer, CPP_CLOSE_SQUARE))
{
error_at (cp_lexer_peek_token (parser->lexer)->location,
"pack index missing");
cp_lexer_consume_token (parser->lexer);
return error_mark_node;
}
tree index = cp_parser_constant_expression (parser,
/*allow_non_constant_p=*/false,
/*non_constant_p=*/nullptr,
/*strict_p=*/true);
/* Consume the ']'. */
cp_parser_require (parser, CPP_CLOSE_SQUARE, RT_CLOSE_SQUARE);
if (TREE_CODE (pack) == TYPE_DECL)
pack = TREE_TYPE (pack);
pack = make_pack_expansion (pack);
return make_pack_index (pack, index);
}
/* Parse a primary-expression.
primary-expression:
@ -6369,6 +6425,11 @@ cp_parser_primary_expression (cp_parser *parser,
= make_location (caret_loc, start_loc, finish_loc);
decl.set_location (combined_loc);
/* "T...[constant-expression]" is a C++26 pack-index-expression. */
if (cp_parser_next_tokens_are_pack_index_p (parser))
decl = cp_parser_pack_index (parser, decl);
return decl;
}
@ -6412,6 +6473,7 @@ missing_template_diag (location_t loc, diagnostic_t diag_kind = DK_WARNING)
id-expression:
unqualified-id
qualified-id
pack-index-expression
qualified-id:
:: [opt] nested-name-specifier template [opt] unqualified-id
@ -6594,7 +6656,9 @@ cp_parser_id_expression (cp_parser *parser,
identifier
operator-function-id
conversion-function-id
~ class-name
literal-operator-id
~ type-name
~ computed-type-specifier
template-id
If TEMPLATE_KEYWORD_P is TRUE, we have just seen the `template'
@ -6901,6 +6965,13 @@ cp_parser_unqualified_id (cp_parser* parser,
"typedef-name %qD used as destructor declarator",
type_decl);
/* "~T...[N]" is a C++26 pack-index-specifier. */
if (cp_parser_next_tokens_are_pack_index_p (parser))
{
type_decl = cp_parser_pack_index (parser, type_decl);
return build_min_nt_loc (loc, BIT_NOT_EXPR, type_decl);
}
return build_min_nt_loc (loc, BIT_NOT_EXPR, TREE_TYPE (type_decl));
}
@ -6971,9 +7042,10 @@ check_template_keyword_in_nested_name_spec (tree name)
class-or-namespace-name :: nested-name-specifier [opt]
class-or-namespace-name :: template nested-name-specifier [opt]
nested-name-specifier: [C++0x]
nested-name-specifier: [C++11]
type-name ::
namespace-name ::
computed-type-specifier ::
nested-name-specifier identifier ::
nested-name-specifier template [opt] simple-template-id ::
@ -7062,8 +7134,8 @@ cp_parser_nested_name_specifier_opt (cp_parser *parser,
if (token->type != CPP_NAME)
break;
/* If the following token is neither a `<' (to begin a
template-id), nor a `::', then we are not looking at a
nested-name-specifier. */
template-id), a `...[' (to begin a pack-index-specifier),
nor a `::', then we are not looking at a nested-name-specifier. */
token = cp_lexer_peek_nth_token (parser->lexer, 2);
if (token->type == CPP_COLON
@ -7081,6 +7153,10 @@ cp_parser_nested_name_specifier_opt (cp_parser *parser,
}
if (token->type != CPP_SCOPE
/* See if a pack-index-specifier follows. */
&& !(token->type == CPP_ELLIPSIS
&& cp_lexer_peek_nth_token (parser->lexer, 3)->type
== CPP_OPEN_SQUARE)
&& !cp_parser_nth_token_starts_template_argument_list_p
(parser, 2))
break;
@ -7445,6 +7521,12 @@ cp_parser_qualifying_entity (cp_parser *parser,
is_declaration,
/*enum_ok=*/cxx_dialect > cxx98);
successful_parse_p = only_class_p || cp_parser_parse_definitely (parser);
/* "T...[constant-expression]" is a C++26 pack-index-specifier. */
if (successful_parse_p
&& cp_parser_next_tokens_are_pack_index_p (parser))
scope = cp_parser_pack_index (parser, scope);
/* If that didn't work, try for a namespace-name. */
if (!only_class_p && !successful_parse_p)
{
@ -17368,6 +17450,10 @@ cp_parser_decltype_expr (cp_parser *parser,
tree id_expression = expr;
cp_id_kind idk;
const char *error_msg;
const bool pack_index_p = cp_parser_next_tokens_are_pack_index_p (parser);
const bool have_id_expr_p
= (pack_index_p
|| cp_lexer_peek_token (parser->lexer)->type == CPP_CLOSE_PAREN);
if (identifier_p (expr))
/* Lookup the name we got back from the id-expression. */
@ -17379,7 +17465,7 @@ cp_parser_decltype_expr (cp_parser *parser,
&& TREE_CODE (expr) != TYPE_DECL
&& (TREE_CODE (expr) != BIT_NOT_EXPR
|| !TYPE_P (TREE_OPERAND (expr, 0)))
&& cp_lexer_peek_token (parser->lexer)->type == CPP_CLOSE_PAREN)
&& have_id_expr_p)
{
/* Complete lookup of the id-expression. */
expr = (finish_id_expression
@ -17407,11 +17493,13 @@ cp_parser_decltype_expr (cp_parser *parser,
}
}
if (expr
&& expr != error_mark_node
&& cp_lexer_peek_token (parser->lexer)->type == CPP_CLOSE_PAREN)
/* We have an id-expression. */
id_expression_or_member_access_p = true;
if (expr && expr != error_mark_node && have_id_expr_p)
{
/* We have an id-expression. */
id_expression_or_member_access_p = true;
if (pack_index_p)
expr = cp_parser_pack_index (parser, expr);
}
}
if (!id_expression_or_member_access_p)
@ -17974,13 +18062,17 @@ cp_parser_mem_initializer (cp_parser* parser)
/* Parse a mem-initializer-id.
mem-initializer-id:
:: [opt] nested-name-specifier [opt] class-name
decltype-specifier (C++11)
class-or-decltype
identifier
class-or-decltype:
nested-name-specifier [opt] type-name
nested-name-specifier template simple-template-id
computed-type-specifier
Returns a TYPE indicating the class to be initialized for the first
production (and the second in C++11). Returns an IDENTIFIER_NODE
indicating the data member to be initialized for the last production. */
production. Returns an IDENTIFIER_NODE indicating the data member to
be initialized for the second production. */
static tree
cp_parser_mem_initializer_id (cp_parser* parser)
@ -18051,10 +18143,15 @@ cp_parser_mem_initializer_id (cp_parser* parser)
/*class_head_p=*/false,
/*is_declaration=*/true);
/* If we found one, we're done. */
if (cp_parser_parse_definitely (parser))
return id;
/* Otherwise, look for an ordinary identifier. */
return cp_parser_identifier (parser);
if (!cp_parser_parse_definitely (parser))
/* Otherwise, look for an ordinary identifier. */
id = cp_parser_identifier (parser);
/* ": T...[N]" is a C++26 pack-index-specifier. */
if (cp_parser_next_tokens_are_pack_index_p (parser))
id = cp_parser_pack_index (parser, id);
return id;
}
/* Overloading [gram.over] */
@ -20472,11 +20569,11 @@ cp_parser_type_specifier (cp_parser* parser,
C++11 Extension:
simple-type-specifier:
auto
decltype ( expression )
char16_t
char32_t
__underlying_type ( type-id )
computed-type-specifier
placeholder-type-specifier
C++17 extension:
@ -20858,6 +20955,12 @@ cp_parser_simple_type_specifier (cp_parser* parser,
type = NULL_TREE;
}
/* "T...[constant-expression]" is a C++26 pack-index-specifier. */
if (type
&& type != error_mark_node
&& cp_parser_next_tokens_are_pack_index_p (parser))
type = cp_parser_pack_index (parser, type);
if (!type && flag_concepts && decl_specs)
{
/* Try for a type-constraint with template arguments. We check
@ -29139,12 +29242,21 @@ cp_parser_base_clause (cp_parser* parser)
/* Parse a base-specifier.
base-specifier:
attribute-specifier-seq [opt] :: [opt] nested-name-specifier [opt]
class-name
attribute-specifier-seq [opt] virtual access-specifier [opt] :: [opt]
nested-name-specifier [opt] class-name
attribute-specifier-seq [opt] access-specifier virtual [opt] :: [opt]
nested-name-specifier [opt] class-name
attribute-specifier-seq [opt] class-or-decltype
attribute-specifier-seq [opt] virtual access-specifier [opt]
class-or-decltype
attribute-specifier-seq [opt] access-specifier virtual [opt]
class-or-decltype
class-or-decltype:
nested-name-specifier [opt] type-name
nested-name-specifier template simple-template-id
computed-type-specifier
access-specifier:
private
protected
public
Returns a TREE_LIST. The TREE_PURPOSE will be one of
ACCESS_{DEFAULT,PUBLIC,PROTECTED,PRIVATE}_[VIRTUAL]_NODE to
@ -29273,6 +29385,9 @@ cp_parser_base_specifier (cp_parser* parser)
/*class_head_p=*/false,
/*is_declaration=*/true);
type = TREE_TYPE (type);
/* ": T...[constant-expression]" is a C++26 pack-index-specifier. */
if (cp_parser_next_tokens_are_pack_index_p (parser))
type = cp_parser_pack_index (parser, type);
}
if (type == error_mark_node)

98
gcc/cp/pt.cc
View file

@ -1788,6 +1788,11 @@ iterative_hash_template_arg (tree arg, hashval_t val)
val = iterative_hash_template_arg (PACK_EXPANSION_PATTERN (arg), val);
return iterative_hash_template_arg (PACK_EXPANSION_EXTRA_ARGS (arg), val);
case PACK_INDEX_TYPE:
case PACK_INDEX_EXPR:
val = iterative_hash_template_arg (PACK_INDEX_PACK (arg), val);
return iterative_hash_template_arg (PACK_INDEX_INDEX (arg), val);
case TYPE_ARGUMENT_PACK:
case NONTYPE_ARGUMENT_PACK:
return iterative_hash_template_arg (ARGUMENT_PACK_ARGS (arg), val);
@ -4030,6 +4035,15 @@ find_parameter_packs_r (tree *tp, int *walk_subtrees, void* data)
*walk_subtrees = 0;
return NULL_TREE;
case PACK_INDEX_TYPE:
case PACK_INDEX_EXPR:
/* We can have an expansion of an expansion, such as "Ts...[Is]...",
so do look into the index (but not the pack). */
cp_walk_tree (&PACK_INDEX_INDEX (t), &find_parameter_packs_r, ppd,
ppd->visited);
*walk_subtrees = 0;
return NULL_TREE;
case INTEGER_TYPE:
cp_walk_tree (&TYPE_MAX_VALUE (t), &find_parameter_packs_r,
ppd, ppd->visited);
@ -4256,6 +4270,36 @@ make_pack_expansion (tree arg, tsubst_flags_t complain)
return result;
}
/* Create a PACK_INDEX_* using the pack expansion PACK and index INDEX. */
tree
make_pack_index (tree pack, tree index)
{
if (pack == error_mark_node)
return error_mark_node;
bool for_types;
if (TREE_CODE (pack) == TYPE_PACK_EXPANSION)
for_types = true;
else if (TREE_CODE (pack) == EXPR_PACK_EXPANSION)
for_types = false;
else
{
/* Maybe we've already partially substituted the pack. */
gcc_checking_assert (TREE_CODE (pack) == TREE_VEC);
for_types = TYPE_P (TREE_VEC_ELT (pack, 0));
}
tree t = (for_types
? cxx_make_type (PACK_INDEX_TYPE)
: make_node (PACK_INDEX_EXPR));
PACK_INDEX_PACK (t) = pack;
PACK_INDEX_INDEX (t) = index;
if (TREE_CODE (t) == PACK_INDEX_TYPE)
SET_TYPE_STRUCTURAL_EQUALITY (t);
return t;
}
/* Checks T for any "bare" parameter packs, which have not yet been
expanded, and issues an error if any are found. This operation can
only be done on full expressions or types (e.g., an expression
@ -13647,11 +13691,12 @@ add_extra_args (tree extra, tree args, tsubst_flags_t complain, tree in_decl)
return args;
}
/* Substitute ARGS into T, which is an pack expansion
(i.e. TYPE_PACK_EXPANSION or EXPR_PACK_EXPANSION). Returns a
/* Substitute ARGS into T, which is a pack expansion
(i.e. TYPE_PACK_EXPANSION or EXPR_PACK_EXPANSION). Returns a
TREE_VEC with the substituted arguments, a PACK_EXPANSION_* node
(if only a partial substitution could be performed) or
ERROR_MARK_NODE if there was an error. */
tree
tsubst_pack_expansion (tree t, tree args, tsubst_flags_t complain,
tree in_decl)
@ -13952,6 +13997,26 @@ tsubst_pack_expansion (tree t, tree args, tsubst_flags_t complain,
return result;
}
/* Substitute ARGS into T, which is a pack index (i.e., PACK_INDEX_TYPE or
PACK_INDEX_EXPR). Returns a single type or expression, a PACK_INDEX_*
node if only a partial substitution could be performed, or ERROR_MARK_NODE
if there was an error. */
tree
tsubst_pack_index (tree t, tree args, tsubst_flags_t complain, tree in_decl)
{
tree pack = PACK_INDEX_PACK (t);
if (PACK_EXPANSION_P (pack))
pack = tsubst_pack_expansion (pack, args, complain, in_decl);
tree index = tsubst_expr (PACK_INDEX_INDEX (t), args, complain, in_decl);
const bool parenthesized_p = (TREE_CODE (t) == PACK_INDEX_EXPR
&& PACK_INDEX_PARENTHESIZED_P (t));
if (!value_dependent_expression_p (index) && TREE_CODE (pack) == TREE_VEC)
return pack_index_element (index, pack, parenthesized_p, complain);
else
return make_pack_index (pack, index);
}
/* Make an argument pack out of the TREE_VEC VEC. */
static tree
@ -16340,7 +16405,8 @@ tsubst (tree t, tree args, tsubst_flags_t complain, tree in_decl)
&& code != TEMPLATE_PARM_INDEX
&& code != IDENTIFIER_NODE
&& code != FUNCTION_TYPE
&& code != METHOD_TYPE)
&& code != METHOD_TYPE
&& code != PACK_INDEX_TYPE)
type = tsubst (type, args, complain, in_decl);
if (type == error_mark_node)
return error_mark_node;
@ -16900,9 +16966,15 @@ tsubst (tree t, tree args, tsubst_flags_t complain, tree in_decl)
ctx = tsubst_pack_expansion (ctx, args,
complain | tf_qualifying_scope,
in_decl);
if (ctx == error_mark_node
|| TREE_VEC_LENGTH (ctx) > 1)
if (ctx == error_mark_node)
return error_mark_node;
if (TREE_VEC_LENGTH (ctx) > 1)
{
if (complain & tf_error)
error ("%qD expanded to more than one element",
TYPENAME_TYPE_FULLNAME (t));
return error_mark_node;
}
if (TREE_VEC_LENGTH (ctx) == 0)
{
if (complain & tf_error)
@ -17077,6 +17149,9 @@ tsubst (tree t, tree args, tsubst_flags_t complain, tree in_decl)
case NONTYPE_ARGUMENT_PACK:
return tsubst_argument_pack (t, args, complain, in_decl);
case PACK_INDEX_TYPE:
return tsubst_pack_index (t, args, complain, in_decl);
case VOID_CST:
case INTEGER_CST:
case REAL_CST:
@ -21869,6 +21944,9 @@ tsubst_expr (tree t, tree args, tsubst_flags_t complain, tree in_decl)
RETURN (r);
}
case PACK_INDEX_EXPR:
RETURN (tsubst_pack_index (t, args, complain, in_decl));
case EXPR_PACK_EXPANSION:
error ("invalid use of pack expansion expression");
RETURN (error_mark_node);
@ -28209,8 +28287,9 @@ dependent_type_p_r (tree type)
}
/* All TYPE_PACK_EXPANSIONs are dependent, because parameter packs must
be template parameters. */
if (TREE_CODE (type) == TYPE_PACK_EXPANSION)
be template parameters. This includes pack-index-specifiers. */
if (TREE_CODE (type) == TYPE_PACK_EXPANSION
|| TREE_CODE (type) == PACK_INDEX_TYPE)
return true;
if (TREE_CODE (type) == DEPENDENT_OPERATOR_TYPE)
@ -28837,6 +28916,11 @@ type_dependent_expression_p (tree expression)
if (TREE_CODE (expression) == EXPR_PACK_EXPANSION)
return true;
/* [temp.dep.expr]: "A pack-index-expression is type-dependent if its
id-expression is type-dependent." */
if (TREE_CODE (expression) == PACK_INDEX_EXPR)
return type_dependent_expression_p (PACK_INDEX_PACK (expression));
if (TREE_TYPE (expression) == unknown_type_node)
{
if (TREE_CODE (expression) == ADDR_EXPR)

5
gcc/cp/ptree.cc
View file

@ -192,6 +192,11 @@ cxx_print_type (FILE *file, tree node, int indent)
print_node (file, "args", PACK_EXPANSION_EXTRA_ARGS (node), indent + 4);
return;
case PACK_INDEX_TYPE:
print_node (file, "pack", PACK_INDEX_PACK (node), indent + 4);
print_node (file, "index", PACK_INDEX_INDEX (node), indent + 4);
return;
default:
return;
}

22
gcc/cp/semantics.cc
View file

@ -2452,6 +2452,8 @@ finish_parenthesized_expr (cp_expr expr)
tree stripped_expr = tree_strip_any_location_wrapper (expr);
if (TREE_CODE (stripped_expr) == STRING_CST)
PAREN_STRING_LITERAL_P (stripped_expr) = 1;
else if (TREE_CODE (stripped_expr) == PACK_INDEX_EXPR)
PACK_INDEX_PARENTHESIZED_P (stripped_expr) = true;
expr = cp_expr (force_paren_expr (expr), expr.get_location ());
@ -4848,24 +4850,38 @@ finish_type_pack_element (tree idx, tree types, tsubst_flags_t complain)
if (TREE_CODE (idx) != INTEGER_CST || !INTEGRAL_TYPE_P (TREE_TYPE (idx)))
{
if (complain & tf_error)
error ("%<__type_pack_element%> index is not an integral constant");
error ("pack index is not an integral constant");
return error_mark_node;
}
if (tree_int_cst_sgn (idx) < 0)
{
if (complain & tf_error)
error ("%<__type_pack_element%> index is negative");
error ("pack index is negative");
return error_mark_node;
}
if (wi::to_widest (idx) >= TREE_VEC_LENGTH (types))
{
if (complain & tf_error)
error ("%<__type_pack_element%> index is out of range");
error ("pack index is out of range");
return error_mark_node;
}
return TREE_VEC_ELT (types, tree_to_shwi (idx));
}
/* In a pack-index T...[N], return the element at index IDX within TYPES.
PARENTHESIZED_P is true iff the pack index was wrapped in (). */
tree
pack_index_element (tree idx, tree types, bool parenthesized_p,
tsubst_flags_t complain)
{
tree r = finish_type_pack_element (idx, types, complain);
if (parenthesized_p)
/* For the benefit of decltype(auto). */
r = force_paren_expr (r);
return r;
}
/* Implement the __direct_bases keyword: Return the direct base classes
of type. */

16
gcc/cp/tree.cc
View file

@ -4277,6 +4277,15 @@ cp_tree_equal (tree t1, tree t2)
return false;
return true;
case PACK_INDEX_EXPR:
if (!cp_tree_equal (PACK_INDEX_PACK (t1),
PACK_INDEX_PACK (t2)))
return false;
if (!cp_tree_equal (PACK_INDEX_INDEX (t1),
PACK_INDEX_INDEX (t2)))
return false;
return true;
case COMPONENT_REF:
/* If we're comparing contract conditions of overrides, member references
compare equal if they designate the same member. */
@ -5617,6 +5626,13 @@ cp_walk_subtrees (tree *tp, int *walk_subtrees_p, walk_tree_fn func,
*walk_subtrees_p = 0;
break;
case PACK_INDEX_TYPE:
case PACK_INDEX_EXPR:
WALK_SUBTREE (PACK_INDEX_PACK (t));
WALK_SUBTREE (PACK_INDEX_INDEX (t));
*walk_subtrees_p = 0;
break;
case CAST_EXPR:
case REINTERPRET_CAST_EXPR:
case STATIC_CAST_EXPR:

6
gcc/cp/typeck.cc
View file

@ -1622,6 +1622,12 @@ structural_comptypes (tree t1, tree t2, int strict)
&& comp_template_args (PACK_EXPANSION_EXTRA_ARGS (t1),
PACK_EXPANSION_EXTRA_ARGS (t2)));
case PACK_INDEX_TYPE:
return (cp_tree_equal (PACK_INDEX_PACK (t1),
PACK_INDEX_PACK (t2))
&& cp_tree_equal (PACK_INDEX_INDEX (t1),
PACK_INDEX_INDEX (t2)));
case DECLTYPE_TYPE:
if (DECLTYPE_TYPE_ID_EXPR_OR_MEMBER_ACCESS_P (t1)
!= DECLTYPE_TYPE_ID_EXPR_OR_MEMBER_ACCESS_P (t2))

102
gcc/testsuite/g++.dg/cpp26/pack-indexing1.C Normal file
View file

@ -0,0 +1,102 @@
// P2662R3 - Pack Indexing
// PR c++/113798
// { dg-do compile { target c++17 } }
// { dg-options "" }
template<class, class> struct same_type;
template<class T> struct same_type<T, T> {};
template<int I, typename... Ts>
using Type = Ts...[I]; // { dg-warning "pack indexing only available with" "" { target c++23_down } }
template<int I, auto... Ts>
constexpr auto Var = Ts...[I]; // { dg-warning "pack indexing only available with" "" { target c++23_down } }
template <int I, auto...Ts>
int
foo ()
{
return Ts...[I]; // { dg-warning "pack indexing only available with" "" { target c++23_down } }
}
template<typename... Ts>
struct S {
Ts...[0] a; // { dg-warning "pack indexing only available with" "" { target c++23_down } }
#if __cpp_concepts >= 201907L
void foo (auto... Vs) {
decltype(Vs...[1]) d1 = Vs...[1]; // { dg-warning "pack indexing only available with" "" { target { c++20 && c++23_down } } }
}
#endif
};
int
g ()
{
using U = Type<1, char, int, float>;
using U = int;
constexpr auto V = Var<2, 0, 1, 42>;
static_assert (V == 42);
U r = foo<2, 0, 1, 42>();
return r;
}
void
fn1 ()
{
int i = 0;
[&i](auto... pack) {
// type is int
decltype(pack...[0]) x5 = 42; // { dg-warning "pack indexing only available with" "" { target c++23_down } }
// type is int&
[[maybe_unused]] decltype((pack...[0])) x6 = i; // { dg-warning "pack indexing only available with" "" { target c++23_down } }
}(0);
}
#if __cpp_concepts >= 201907L
int
bar (auto... pack)
{
(void) pack...[0]; // { dg-warning "pack indexing only available with" "" { target { c++20 && c++23_down } } }
int x = pack...[0]; // { dg-warning "pack indexing only available with" "" { target { c++20 && c++23_down } } }
return x;
}
#endif
template<auto...pack>
void
fn2 ()
{
[[maybe_unused]] decltype(pack...[0]) x1; // { dg-warning "pack indexing only available with" "" { target c++23_down } }
[[maybe_unused]] decltype((pack...[0])) x2; // { dg-warning "pack indexing only available with" "" { target c++23_down } }
same_type<decltype(x1), int>();
same_type<decltype(x2), int>();
}
template<typename... T>
void
fn3 (int p)
{
T...[0] a = p; // { dg-warning "pack indexing only available with" "" { target c++23_down } }
(T...[0])(a); // { dg-warning "pack indexing only available with" "" { target c++23_down } }
}
template<int... Is>
void fn4 ()
{
same_type<decltype(Is...[0]), int>(); // { dg-warning "pack indexing only available with" "" { target c++23_down } }
same_type<decltype((Is...[0])), int>(); // { dg-warning "pack indexing only available with" "" { target c++23_down } }
}
void
g3 ()
{
fn2<0>();
#if __cpp_concepts >= 201907L
bar (0);
#endif
S<int> s;
fn4<0, 1, 2>();
}

15
gcc/testsuite/g++.dg/cpp26/pack-indexing10.C Normal file
View file

@ -0,0 +1,15 @@
// P2662R3 - Pack Indexing
// PR c++/113798
// { dg-do compile { target c++26 } }
template<auto... Vs>
constexpr auto f() {
return []<int N>() { return Vs...[N]; }.template operator()<1>();
}
static_assert(f<1, 2, 3>() == 2);
template<int N>
constexpr auto g() {
return []<auto... Vs>() { return Vs...[N]; }.template operator()<1, 2, 3>();
}
static_assert(g<1>() == 2);

13
gcc/testsuite/g++.dg/cpp26/pack-indexing11.C Normal file
View file

@ -0,0 +1,13 @@
// P2662R3 - Pack Indexing
// PR c++/113798
// { dg-do compile { target c++26 } }
// Test case from [diff.cpp23.dcl.dcl].
template <typename... T>
void f(T... [1]);
template <typename... T>
void g(T... ptr[1]);
int main() {
f<int, double>(nullptr, nullptr); // { dg-error "no matching function" }
g<int, double>(nullptr, nullptr); // ok
}

111
gcc/testsuite/g++.dg/cpp26/pack-indexing2.C Normal file
View file

@ -0,0 +1,111 @@
// P2662R3 - Pack Indexing
// PR c++/113798
// { dg-do compile { target c++26 } }
// Test invalid cases.
template<int I, typename... Ts>
using Type = Typo...[I]; // { dg-error "does not name a type" }
template<int I, auto... Ts>
constexpr auto Var = Typo...[I]; // { dg-error "no parameter packs" }
template<typename... Ts>
void foo(Ts...[]); // { dg-error "pack index missing" }
template <typename... Ts>
void f(Ts...[1]);
template<int... N>
int f2 (X... [N]); // { dg-error "contains no parameter packs" }
struct X;
template<typename T>
struct TX;
template <typename T, auto V, template<typename> typename Tp>
void
bad (int i)
{
i...[0]; // { dg-error "no parameter packs" }
V...[0]; // { dg-error "no parameter packs" }
X...[0] x; // { dg-error "no parameter packs" }
T...[0] t; // { dg-error "no parameter packs" }
Tp...[0] tp; // { dg-error "expected" }
X...[0] xarr[1]; // { dg-error "no parameter packs" }
T...[0] tarr[1]; // { dg-error "no parameter packs" }
Tp...[0] tparr[1]; // { dg-error "expected" }
}
template<int N>
int
getT (auto... Ts)
{
return Ts...[N]; // { dg-error "pack index is out of range" }
}
template<int N>
int
getT2 (auto... Ts)
{
return Ts...[N]; // { dg-error "pack index is negative" }
}
template<auto N, typename... Ts>
void
badtype ()
{
Ts...[N] t; // { dg-error "pack index is out of range" }
}
template<auto N, typename... Ts>
void
badtype2 ()
{
Ts...[N] t; // { dg-error "pack index is negative" }
}
int nonconst () { return 42; }
template<typename... Ts>
void
badindex ()
{
Ts...[nonconst ()] t; // { dg-error "pack index is not an integral constant" }
// { dg-error "non-.constexpr. function" "" { target *-*-* } .-1 }
}
template<typename... Ts>
struct broken {
Ts...1; // { dg-error "expected" }
Ts...[; // { dg-error "invalid" }
Ts...[1; // { dg-error "invalid" }
Ts...[]; // { dg-error "pack index missing" }
void foo (auto...Vs) {
decltype(Vs...[1]) d1 = Vs...[]; // { dg-error "pack index missing" }
decltype(Vs...[1]) d2 = Vs...[; // { dg-error "expected" }
}
};
int main()
{
// void f<int, double>(int [1], double [1])
f<int, double>(nullptr, nullptr); // { dg-error "no matching function" }
bad<int, 0, TX>(42);
getT<0>(); // { dg-message "required from here" }
getT<1>(); // { dg-message "required from here" }
getT2<-1>(); // { dg-message "required from here" }
badtype<0>(); // { dg-message "required from here" }
badtype<1, int>(); // { dg-message "required from here" }
badtype2<-1>(); // { dg-message "required from here" }
badtype2<-1, int>(); // { dg-message "required from here" }
badindex<int, int, int>();
bool b = nothere...[0]; // { dg-error "no parameter packs" }
using E = nothere...[0]; // { dg-error "does not name a type" }
}

41
gcc/testsuite/g++.dg/cpp26/pack-indexing3.C Normal file
View file

@ -0,0 +1,41 @@
// P2662R3 - Pack Indexing
// PR c++/113798
// { dg-do compile { target c++26 } }
// From LLVM's cxx2c-pack-indexing.cpp.
template<typename...>
struct X { };
template<typename... T>
requires requires(T...[0]) { {T...[0](0)}; }
struct S : T...[1] {
[[maybe_unused]] T...[1] base = {};
using foo = T...[1];
S() : T...[1]() { }
X<T...[0]> x;
const T...[0] f(T...[0]&& parm) noexcept((T...[0])0) {
T...[0] (*test)(const volatile T...[0]**);
thread_local T...[0] d;
[[maybe_unused]] T...[0] a = parm;
auto ptr = new T...[0](0);
(*ptr).~T...[0]();
return T...[0](0);
typename T...[1]::foo b = 0;
T...[1]::i = 0;
return (T...[0])(a);
new T...[0];
[[maybe_unused]] auto l = []<T...[0]>(T...[0][1]) -> T...[0]{ return {}; };
[[maybe_unused]] auto _ = l.template operator()<T...[0]{}>({0});
}
operator T...[0]() const { }
};
struct base {
using foo = int;
static inline int i = 42;
};
int main()
{
S<int, base>().f(0);
}

65
gcc/testsuite/g++.dg/cpp26/pack-indexing4.C Normal file
View file

@ -0,0 +1,65 @@
// P2662R3 - Pack Indexing
// PR c++/113798
// { dg-do compile { target c++26 } }
// From LLVM's cxx2c-pack-indexing.cpp.
template <class, class>
constexpr bool is_same = false;
template <class T>
constexpr bool is_same<T, T> = true;
template <typename T>
constexpr bool
f (auto&&... p)
{
return is_same<T, decltype(p...[0])>;
}
void
g ()
{
int a = 0;
const int b = 0;
static_assert(f<int&&>(0));
static_assert(f<int&>(a));
static_assert(f<const int&>(b));
}
template<auto... p>
struct A {
enum E {
x = p...[0]
};
};
static_assert(A<42>::x == 42);
struct S { };
template<auto... p>
constexpr auto constant_initializer = p...[0];
constexpr auto InitOk = constant_initializer<S{}>;
consteval int evaluate(auto... p) {
return p...[0];
}
constexpr int x = evaluate(42, S{});
static_assert(x == 42);
template <auto... Is>
struct IL{};
template <typename... Ts>
struct TL{};
template <typename Tl, typename Il>
struct SpliceImpl;
template <typename... Ts, auto... Is>
struct SpliceImpl<TL<Ts...>, IL<Is...>>
{
using type = TL<Ts...[Is]...>;
};
template <typename Tl, typename Il>
using Splice = typename SpliceImpl<Tl, Il>::type;
using type = Splice<TL<char, short, long, double>, IL<1, 2>>;
static_assert(is_same<type, TL<short, long>>);

41
gcc/testsuite/g++.dg/cpp26/pack-indexing5.C Normal file
View file

@ -0,0 +1,41 @@
// P2662R3 - Pack Indexing
// PR c++/113798
// { dg-do compile { target c++26 } }
template<class, class> struct same_type;
template<class T> struct same_type<T, T> {};
void
fn1 (auto... Ts)
{
same_type<decltype(Ts...[0]), int>();
same_type<decltype((Ts...[0])), int&>();
same_type<decltype(Ts...[1]), unsigned int>();
same_type<decltype((Ts...[1])), unsigned int&>();
}
template<auto... Is>
void
fn2 ()
{
same_type<decltype(Is...[0]), int>();
same_type<decltype((Is...[0])), int>();
same_type<decltype(Is...[1]), unsigned int>();
same_type<decltype((Is...[1])), unsigned int>();
same_type<decltype(Is...[2]), double>();
same_type<decltype((Is...[2])), double>();
same_type<decltype(Is...[3]), float>();
same_type<decltype((Is...[3])), float>();
same_type<decltype(Is...[4]), unsigned char>();
same_type<decltype((Is...[4])), unsigned char>();
}
static constexpr unsigned char c = 'A';
void
g ()
{
int i = 42;
fn1 (i, 42u);
fn2<0, 1u, 2.0, 3.f, c>();
}

51
gcc/testsuite/g++.dg/cpp26/pack-indexing6.C Normal file
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@ -0,0 +1,51 @@
// P2662R3 - Pack Indexing
// PR c++/113798
// { dg-do compile { target c++26 } }
template<class, class> struct same_type;
template<class T> struct same_type<T, T> {};
void
fn1 (auto... Ts)
{
decltype(auto) a1 = Ts...[0];
same_type<decltype(a1), int>();
decltype(auto) a2 = (Ts...[0]);
same_type<decltype(a2), int&>();
}
template<auto... Is>
void
fn2 ()
{
decltype(auto) a1 = Is...[0];
same_type<decltype(a1), int>();
decltype(auto) a2 = (Is...[0]);
same_type<decltype(a2), int>();
decltype(auto) a3 = Is...[1];
same_type<decltype(a3), unsigned int>();
decltype(auto) a4 = (Is...[1]);
same_type<decltype(a4), unsigned int>();
decltype(auto) a5 = Is...[2];
same_type<decltype(a5), double>();
decltype(auto) a6 = (Is...[2]);
same_type<decltype(a6), double>();
decltype(auto) a7 = Is...[3];
same_type<decltype(a7), float>();
decltype(auto) a8 = (Is...[3]);
same_type<decltype(a8), float>();
decltype(auto) a9 = Is...[4];
same_type<decltype(a9), unsigned char>();
decltype(auto) a10 = (Is...[4]);
same_type<decltype(a10), unsigned char>();
}
static constexpr unsigned char c = 'A';
void
g ()
{
int i = 42;
fn1 (i, 42u);
fn2<0, 1u, 2.0, 3.f, c>();
}

16
gcc/testsuite/g++.dg/cpp26/pack-indexing7.C Normal file
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@ -0,0 +1,16 @@
// P2662R3 - Pack Indexing
// PR c++/113798
// { dg-do compile { target c++26 } }
template <int I, auto...Ts>
decltype(Ts...[I])
foo () // { dg-bogus "sorry, unimplemented: mangling" "" { xfail *-*-* } }
{
return Ts...[I];
}
int
g ()
{
return foo<2, 0, 1, 42>();
}

23
gcc/testsuite/g++.dg/cpp26/pack-indexing8.C Normal file
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@ -0,0 +1,23 @@
// P2662R3 - Pack Indexing
// PR c++/113798
// { dg-do run { target c++26 } }
#include <initializer_list>
template<typename... Ts>
int
g (auto... Is)
{
std::initializer_list<Ts...[0]> l{ Is...[0], Is...[1], Is...[2], Is...[3], Is...[4] };
int sum = 0;
for (auto x : l)
sum += x;
return sum;
}
int
main ()
{
if (g<int> (1, 2, 3, 4, 5) != 15)
__builtin_abort ();
}

27
gcc/testsuite/g++.dg/cpp26/pack-indexing9.C Normal file
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@ -0,0 +1,27 @@
// P2662R3 - Pack Indexing
// PR c++/113798
// { dg-do compile { target c++26 } }
// From <https://github.com/itanium-cxx-abi/cxx-abi/issues/175>.
template <class... T> struct tuple {
template <unsigned I> T...[I] get(); // { dg-bogus "sorry, unimplemented: mangling" "" { xfail *-*-* } }
};
int
g ()
{
tuple<int> t;
return t.get<0>();
}
template<typename T, typename U> concept C = true;
template<typename ...T> struct A {
template<int I, typename ...U> void f(T...[I], U...[I]) requires C<T...[I], U...[I]>; // { dg-message "sorry, unimplemented: mangling" }
};
void
h ()
{
A<char, int, double> a;
a.f<1, int, int, char>(1, 2);
}

18
gcc/testsuite/g++.dg/modules/pack-index-1_a.C Normal file
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@ -0,0 +1,18 @@
// { dg-module-do run }
// { dg-additional-options { -std=c++26 -fmodules-ts } }
export module packing1;
// { dg-module-cmi "packing1" }
export template<int I, typename... Ts>
using Type = Ts...[I];
export template<int I, auto... Ts>
constexpr auto Var = Ts...[I];
export template <int I, auto...Ts>
int
foo ()
{
return Ts...[I];
}

15
gcc/testsuite/g++.dg/modules/pack-index-1_b.C Normal file
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// { dg-additional-options { -std=c++26 -fmodules-ts } }
import packing1;
int
main ()
{
using U = Type<1, char, int, float>;
using U = int;
U r = foo<2, 0, 1, 42>();
constexpr auto V = Var<2, 0, 1, 42>;
static_assert (V == 42);
}

2
libstdc++-v3/testsuite/20_util/tuple/element_access/get_neg.cc
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@ -61,4 +61,4 @@ test03()
// { dg-error "tuple index must be in range" "" { target *-*-* } 0 }
// { dg-prune-output "no type named 'type' in .*_Nth_type" }
// { dg-prune-output "'__type_pack_element' index is out of range" }
// { dg-prune-output "pack index is out of range" }