mixin has been expanded to accept any number of arguments that are being concatenated. This should also work with an AliasSeq. alias seq = AliasSeq!("a +", 1); a = mixin(seq); should behave the same way as a = mixin("a +", 1); The generated error message "Error: undefined identifier `tuple`" is rather confusing.
This was fixed recently : https://github.com/dlang/dmd/pull/9521 *** This issue has been marked as a duplicate of issue 19775 ***