https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65075
--- Comment #1 from Paolo Carlini <paolo.carlini at oracle dot com> --- Hi Jakub. Something like the below passes testing and works for the testcase: Index: constexpr.c =================================================================== --- constexpr.c (revision 220731) +++ constexpr.c (working copy) @@ -415,8 +415,8 @@ check_constexpr_bind_expr_vars (tree t) gcc_assert (TREE_CODE (t) == BIND_EXPR); for (tree var = BIND_EXPR_VARS (t); var; var = DECL_CHAIN (var)) - if (TREE_CODE (var) == TYPE_DECL - && DECL_IMPLICIT_TYPEDEF_P (var)) + if (DECL_IMPLICIT_TYPEDEF_P (var) + && !LAMBDA_TYPE_P (TREE_TYPE (var))) return false; return true; } Note that I will be traveling for a week or so, thus I'm not be able to fully handle the issue. If we rather resolve the regression immediately, please feel free to pick up the above / double check if it makes sense to Jason.