https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123667
--- Comment #4 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Jakub Jelinek <[email protected]>: https://gcc.gnu.org/g:34a47a8b14e2a74d35a65ccc2bd2a166106b9b96 commit r16-7012-g34a47a8b14e2a74d35a65ccc2bd2a166106b9b96 Author: Jakub Jelinek <[email protected]> Date: Sat Jan 24 10:36:45 2026 +0100 c++: Fix ICE on decltype on non-local structured binding inside of a template [PR123667] The following testcases ICE when decltype (x) appears in a template where x is a tuple based structured binding from outside of that template (one testcase shows the sb in a function and template is a lambda within that function, the other shows namespace scope sb referenced from a template). What I wrote in the comment there is true only for structured bindings within the current template function, in that case that structured binding indeed has to have DECL_VALUE_EXPR and lookup_decomp_type might return NULL or might not and depending on that we should choose if it is a tuple based structured binding and return its type or if we should return unlowered type of expr. But if decltype in a template refers to a structured binding elsewhere, it could have been finalized already and determined to be tuple based structured binding, so DECL_HAVE_VALUE_EXPR_P can be false in that case. In that case, if ptds.saved would be false, we'd just always return lookup_decomp_type. So, for this case the patch allows that case in the assert and asserts lookup_decomp_type returned non-NULL. 2026-01-24 Jakub Jelinek <[email protected]> PR c++/123667 * semantics.cc (finish_decltype_type): Allow a structured binding for ptds.saved to have DECL_HAS_VALUE_EXPR_P cleared, if it is not within current_function_decl, but in that case assert that lookup_decomp_type succeeded. * g++.dg/cpp1z/decomp66.C: New test. * g++.dg/cpp1z/decomp67.C: New test.
