The value to check
True if value reduces to a vacuous placeholder under recursive elision; false otherwise
Vacuousness is a semantic property that crosscuts the template structural types and admits selection-only
objects (for example { "<price": 100 }, whose slot value is itself non-vacuous), so there is no coherent
type to narrow to. The guard therefore narrows only to undefined | object, the broadest sound target: a
true result guarantees merely that value is not a primitive Literal leaf.
Checks if a value is vacuous per the template elision rule.
A placeholder is vacuous when, after recursive elision, it carries no retrieval instructions and must be ignored as if the owning field were omitted from the enclosing template:
undefined{})"") mapping to a vacuous value — transitively elided per the rule, leaving at most a selection-only innerPrimitive placeholders (Literal) are never vacuous — they are type markers for leaf retrieval.