expand_explain_doc_comment_outer =
    outer doc comments expand to `#[doc = "..."]`, which is what this macro attempted to match

expand_explain_doc_comment_inner =
    inner doc comments expand to `#![doc = "..."]`, which is what this macro attempted to match

expand_expr_repeat_no_syntax_vars = 
    attempted to repeat an expression containing no syntax variables matched as repeating at this depth

expand_must_repeat_once = 
    this must repeat at least once

count_repetition_misplaced =
    `count` can not be placed inside the inner-most repetition