Module ids 

Strongly typed IDs.

Every stable identity in the IR is an Id<T>: an opaque newtype over a u32 arena index, tagged with the type it references. The type parameter makes it impossible to pass, say, an expression ID where a rule ID is expected, while Id<T> remains cheap, comparable, and hashable.

IDs are produced by Arena::push and are stable for the lifetime of the arena. They are never dereferenced directly: lookup goes through the owning arena, which bounds-checks and returns Option, so an invalid or dangling ID is a recoverable invariant error rather than a panic.

Structs

Id

A typed, stable index into an Arena.

Traits

IdLike

Any typed ID: exposes the arena index, usable in generic contexts.