https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120775
--- Comment #4 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The trunk branch has been updated by Marek Polacek <mpola...@gcc.gnu.org>: https://gcc.gnu.org/g:d46d8267b5a55e3194e879e691aeee1bc0648bed commit r16-2687-gd46d8267b5a55e3194e879e691aeee1bc0648bed Author: Marek Polacek <pola...@redhat.com> Date: Mon Jul 14 17:24:18 2025 -0400 c++: consteval blocks This patch implements consteval blocks, as specified by P2996. They aren't very useful without define_aggregate, but having a reviewed implementation on trunk would be great. consteval {} can be anywhere where a member-declaration or block-declaration can be. The expression corresponding to it is: [] -> void static consteval compound-statement () and it must be a constant expression. I've used cp_parser_lambda_expression to take care of most of the parsing. Since a consteval block can find itself in a template, we need a vehicle to carry the block for instantiation. Rather than inventing a new tree, I'm using STATIC_ASSERT. A consteval block can't return a value but that is checked by virtue of the lambda having a void return type. PR c++/120775 gcc/cp/ChangeLog: * constexpr.cc (cxx_eval_outermost_constant_expr): Use extract_call_expr. * cp-tree.h (CONSTEVAL_BLOCK_P, LAMBDA_EXPR_CONSTEVAL_BLOCK_P): Define. (finish_static_assert): Adjust declaration. (current_nonlambda_function): Likewise. * lambda.cc (current_nonlambda_function): New parameter. Only keep iterating if the function represents a consteval block. * parser.cc (cp_parser_lambda_expression): New parameter for consteval blocks. Use it. Set LAMBDA_EXPR_CONSTEVAL_BLOCK_P. (cp_parser_lambda_declarator_opt): Likewise. (build_empty_string): New. (cp_parser_next_tokens_are_consteval_block_p): New. (cp_parser_consteval_block): New. (cp_parser_block_declaration): Handle consteval blocks. (cp_parser_static_assert): Use build_empty_string. (cp_parser_member_declaration): Handle consteval blocks. * pt.cc (tsubst_stmt): Adjust a call to finish_static_assert. * semantics.cc (finish_fname): Warn for consteval blocks. (finish_static_assert): New parameter for consteval blocks. Set CONSTEVAL_BLOCK_P. Evaluate consteval blocks specially. gcc/testsuite/ChangeLog: * g++.dg/cpp26/consteval-block1.C: New test. * g++.dg/cpp26/consteval-block2.C: New test. * g++.dg/cpp26/consteval-block3.C: New test. * g++.dg/cpp26/consteval-block4.C: New test. * g++.dg/cpp26/consteval-block5.C: New test. * g++.dg/cpp26/consteval-block6.C: New test. * g++.dg/cpp26/consteval-block7.C: New test. * g++.dg/cpp26/consteval-block8.C: New test. Reviewed-by: Jason Merrill <ja...@redhat.com>
