Type Alias SpliceSpan 

pub type SpliceSpan = Option<Box<SpliceSpanPayload>>;

The reduce-time container span a NodeValue::Splice carries up to the parent that drains it: a (start, end) pair of (line, column, pos) triples. Lark keeps the spliced _-rule as a Tree(_rule) and its parent reads that Tree’s container_* meta; our flat Splice carries the same span here instead. None when the _-rule has no positioned raw child (an Empty _rule meta — the parent skips it). Meaningful only mid-reduce: it is None in propagate_positions=off (zero-cost) and irrelevant once a Splice is drained.

Boxed so it costs one pointer, not 28 bytes, in the NodeValue enum: Splice is the widest variant, so an inline span set size_of::<NodeValue>() to 56; boxing shrinks it to 32 (the value stack + arena are the hottest parse structures, so their per-node width is load-bearing — measured calc parse-basic −0.018 ms). The Box is allocated only when a positioned or poisoned _-rule reduces in propagate_positions=on mode; off-mode keeps None and never allocates.

Aliased Type

pub enum SpliceSpan {
    None,
    Some(Box<SpliceSpanPayload>),
}

Variants

None

No value.

Some(Box<SpliceSpanPayload>)

Some value of type T.