2019-11-27 Andrew Sutton <asutton@lock3software.com>
PR c++/92439
Improve quality of diagnostics for subexpressions that need parens.
gcc/cp/
* parser.c (cp_parser_requires_clause_opt): Add a flag to indicate
when parsing a requires-clause before lambda parameters, and...
(cp_parser_lambda_declarator_opt): ... use that here ...
(cp_parser_type_parameter): ... and here ...
(cp_parser_late_return_type_opt): ... and here ...
(cp_parser_explicit_template_declaration): ... and here.
(cp_parser_diagnose_ungrouped_constraint_plain): Adjust the message
because this can apply to subexpressions that are not immediately
after a requires-clause.
(cp_parser_diagnose_ungrouped_constraint_rich): Likewise.
(primary_constraint_error): New.
(cp_parser_constraint_requires_parens): New.
(cp_parser_unary_constraint_requires_parens): New.
(cp_parser_constraint_primary_expression): Check for unary expressions
before parsing the primary expression. Also check for binary and
postfix operators after a successful parse of the primary expression.
Force a re-parse if the result would form a lower-precedence string.
(cp_parser_constraint_logical_and_expression): Propagate lambda flag;
move checks for ill-formed constraints into the constraint primary
expression.
(cp_parser_constraint_logical_or_expression): Likewise.
(cp_parser_requires_clause_expression): Propagate lambda flag.
gcc/testsuite/
* g++.dg/cpp2a/concepts-requires20.C: New.
From-SVN: r278774
