Module rustc_span::def_id[][src]


A DefId identifies a particular definition, by combining a crate index and a def index.

A DefIndex is an index into the hir-map for a crate, identifying a particular definition. It should really be considered an interned shorthand for a particular DefPath.

A DefPathHash is a fixed-size representation of a DefPath that is stable across crate and compilation session boundaries. It consists of two separate 64-bit hashes. The first uniquely identifies the crate this DefPathHash originates from (see StableCrateId), and the second uniquely identifies the corresponding DefPath within that crate. Together they form a unique identifier within an entire crate graph.

A LocalDefId is equivalent to a DefId with krate == LOCAL_CRATE. Since we encode this information in the type, we can ensure at compile time that no DefIds from upstream crates get thrown into the mix. There are quite a few cases where we know that only DefIds from the local crate are expected and a DefId from a different crate would signify a bug somewhere. This is when LocalDefId comes in handy.

A StableCrateId is a 64 bit hash of the crate name combined with all -Cmetadata arguments. It is to CrateNum what DefPathHash is to DefId. It is stable across compilation sessions.


The crate root is always assigned index 0 by the AST Map code, thanks to NodeCollector::new.

Item definitions in the currently-compiled crate would have the CrateNum LOCAL_CRATE in their DefId.



Type Definitions