Module hygiene 

Machinery for hygienic macros.

Inspired by Matthew Flatt et al., “Macros That Work Together: Compile-Time Bindings, Partial Expansion, and Definition Contexts,” Journal of Functional Programming 22, no. 2 (March 1, 2012): 181–216, https://doi.org/10.1017/S0956796812000093.

Structs

ExpnData

A subset of properties from both macro definition and macro call available through global data. Avoid using this if you have access to the original definition or call structures.

ExpnHash

A unique hash value associated to an expansion.

ExpnId

A unique ID associated with a macro invocation and expansion.

ExpnIndex

A unique ID associated with a macro invocation and expansion.

HygieneData 🔒

HygieneDecodeContext

Additional information used to assist in decoding hygiene data

HygieneEncodeContext

HygieneRemappingResults

LocalExpnId

A unique ID associated with a macro invocation and expansion.

LocalExpnIdRemapper

SyntaxContext

A SyntaxContext represents a chain of pairs (ExpnId, Transparency) named “marks”.

SyntaxContextData 🔒

SyntaxContextRemapper

Enums

AstPass

The kind of AST transform.

DesugaringKind

The kind of compiler desugaring.

ExpnKind

Expansion kind.

MacroKind

The kind of macro invocation or definition.

Transparency

A property of a macro expansion that determines how identifiers produced by that expansion are resolved.

Traits

HygieneRemapper

Includes common logic for remapping both expansion ids and syntax contexts. FIXME: this solution does not take into account syntax contexts and expansion ids that are allocated during metadata encoding, if we will have non-determinism there this remapping will not help as it is constructed before metadata encoding.

Functions

debug_hygiene_data

decode_expn_id

Decode an expansion from the metadata of a foreign crate.

decode_syntax_context

register_expn_id

Register an expansion which has been decoded from the metadata of a foreign crate.

register_local_expn_id

Register an expansion which has been decoded from the on-disk-cache for the local crate.

update_disambiguator 🔒

Updates the disambiguator field of the corresponding ExpnData such that the Fingerprint of the ExpnData does not collide with any other ExpnIds.

update_dollar_crate_names

walk_chain

walk_chain_collapsed

In order to have good line stepping behavior in debugger, for the given span we return its outermost macro call site that still has a #[collapse_debuginfo(yes)] property on it. We also stop walking call sites at the function body level because no line stepping can occur at the level above that. The returned span can then be used in emitted debuginfo.

Type Aliases

SyntaxContextKey

If this part of two syntax contexts is equal, then the whole syntax contexts should be equal. The other fields are only for caching.