Type Alias SemanticsShell 

pub type SemanticsShell = Vec<Option<usize>>;

One shell’s worth of semantic-surface indices, one per surface. None — a whole shell with no semantics — is null in JSON, which geomprimitives.schema.json permits at every level of semantics.values ("type": ["array", "null"]), exactly as it does for material.values.

Aliased Type

pub struct SemanticsShell { /* private fields */ }