fn __action20<'i, L>(
    ctx: &ParseContext,
    (_, _, _): (LexerPosition, Token, LexerPosition),
    (_, __0, _): (LexerPosition, Expr, LexerPosition),
    (_, _, _): (LexerPosition, Token, LexerPosition),
) -> ArraySpecifierDimensionDatawhere
    L: HasLexerError,