start is inclusive, end exclusive, both in UTF-16 code units into the
original notation string. The parser sets both on every node it produces;
they are typed optional so hand-constructed ASTs (tests, programmatic
consumers) remain valid without positions.
Source span carried by every AST node.
startis inclusive,endexclusive, both in UTF-16 code units into the original notation string. The parser sets both on every node it produces; they are typed optional so hand-constructed ASTs (tests, programmatic consumers) remain valid without positions.