When lambdas were added in C++11 they were banned from unevaluated contexts
as a way to avoid needing to deal with them in mangling or SFINAE. This
proposal avoids that with a more narrow proposal: lambdas never compare as
equivalent (so we don't need to mangle them), and substitution failures
within a lambda are hard errors. Lambdas appearing in places that types
couldn't previously have been declared introduces various complications; in
particular, it seems likely to mean types with no linkage being used more
broadly, risking ODR violations. I want to follow up this patch with some
related diagnostics.
* decl2.c (min_vis_expr_r): Handle LAMBDA_EXPR.
* mangle.c (write_expression): Handle LAMBDA_EXPR.
* parser.c (cp_parser_lambda_expression): Allow lambdas in
unevaluated context. Start the tentative firewall sooner.
(cp_parser_lambda_body): Use cp_evaluated.
* pt.c (iterative_hash_template_arg): Handle LAMBDA_EXPR.
(tsubst_function_decl): Substitute a lambda even if it isn't
dependent.
(tsubst_lambda_expr): Use cp_evaluated. Always complain.
(tsubst_copy_and_build) [LAMBDA_EXPR]: Do nothing if tf_partial.
* semantics.c (begin_class_definition): Allow in template parm list.
* tree.c (strip_typedefs_expr): Pass through LAMBDA_EXPR.
(cp_tree_equal): Handle LAMBDA_EXPR.
From-SVN: r266056
