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c++: lambda template in requires [PR105541]

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Since the patch for PR103408, the template parameters for the lambda in this
test have level 1 instead of 2, and we were treating null template args as 1
level of arguments, so tsubst_template_parms decided it had nothing to do.
Fixed by distinguishing between <> and no args at all, which is what we have
in our "substitution" in a requires-expression.

	PR c++/105541

gcc/cp/ChangeLog:

	* cp-tree.h (TMPL_ARGS_DEPTH): 0 for null args.
	* parser.cc (cp_parser_enclosed_template_argument_list):
	Use 0-length TREE_VEC for <>.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp2a/lambda-requires1.C: New test.
This commit is contained in:
Jason Merrill 2022-05-11 14:53:26 -04:00
parent 4dc86f716f
commit 88459c3965
3 changed files with 15 additions and 6 deletions
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12
gcc/cp/cp-tree.h
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@ -3771,11 +3771,13 @@ struct GTY(()) lang_decl {
/* The depth of a template argument vector. When called directly by
the parser, we use a TREE_LIST rather than a TREE_VEC to represent
template arguments. In fact, we may even see NULL_TREE if there
are no template arguments. In both of those cases, there is only
one level of template arguments. */
#define TMPL_ARGS_DEPTH(NODE) \
(TMPL_ARGS_HAVE_MULTIPLE_LEVELS (NODE) ? TREE_VEC_LENGTH (NODE) : 1)
template arguments. In that case, there is only one level of template
arguments. We may even see NULL_TREE if there are 0 levels of
template arguments, as in cp_parser_requires_expression. */
#define TMPL_ARGS_DEPTH(NODE) \
((NODE) == NULL_TREE ? 0 \
: TMPL_ARGS_HAVE_MULTIPLE_LEVELS (NODE) ? TREE_VEC_LENGTH (NODE) \
: 1)
/* The LEVELth level of the template ARGS. The outermost level of
args is level 1, not level 0. */

5
gcc/cp/parser.cc
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@ -32151,7 +32151,10 @@ cp_parser_enclosed_template_argument_list (cp_parser* parser)
|| cp_lexer_next_token_is (parser->lexer, CPP_RSHIFT)
|| cp_lexer_next_token_is (parser->lexer, CPP_GREATER_EQ)
|| cp_lexer_next_token_is (parser->lexer, CPP_RSHIFT_EQ))
arguments = NULL_TREE;
{
arguments = make_tree_vec (0);
SET_NON_DEFAULT_TEMPLATE_ARGS_COUNT (arguments, 0);
}
else
arguments = cp_parser_template_argument_list (parser);
/* Look for the `>' that ends the template-argument-list. If we find

4
gcc/testsuite/g++.dg/cpp2a/lambda-requires1.C Normal file
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@ -0,0 +1,4 @@
// PR c++/105541
// { dg-do compile { target c++20 } }
static_assert(requires { []<typename T>{}; });