orphan:

Abstract Syntax Trees (ASTs)

By default, an AST is either:

• a value, for simple elements such as token, pattern, or constant

• a tuple, for closures, gatherings, and the right-hand-side of rules with more than one element but without named elements

• a dict-derived object (AST) that contains one item for every named element in the grammar rule, with items can be accessed through the standard dict syntax (ast['key']), or as attributes (ast.key).

AST entries are single values if only one item was associated with a name, or tuple if more than one item was matched. There’s a provision in the grammar syntax (the +: operator) to force an AST entry to be a tuple even if only one element was matched. The value for named elements that were not found during the parse (perhaps because they are optional) is None.

When the parseinfo=True keyword argument has been passed to the Parser constructor or enabled with the @@parseinfo directive, a parseinfo item is added to AST nodes that are dict-like. The item contains a collections.namedtuple with the parse information for the node:

class ParseInfo(NamedTuple):
    cursor: Cursor
    rule: str
    pos: int
    endpos: int
    line: int
    endline: int
    alerts: list[Alert] = []  # noqa: RUF012

With the help of the cursor: Cusrosr attribute, it’s possible to recover the line, column, and original text parsed for the node.

Generation of parseinfo can also be controlled using the @@parseinfo :: True grammar directive.