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

HygieneDecodeContextInner 🔒

Additional information used to assist in decoding hygiene data

HygieneEncodeContext

LocalExpnId

A unique ID associated with a macro invocation and expansion.

SyntaxContext

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

SyntaxContextData

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.

Functions

assert_default_hashing_controls 🔒

Assert that the provided HashStableContext is configured with the ‘default’ HashingControls. We should always have bailed out before getting to here with a non-default mode. With this check in place, we can avoid the need to maintain separate versions of ExpnData hashes for each permutation of HashingControls settings.

debug_hygiene_data

decode_expn_id

Decode an expansion from the metadata of a foreign crate.

decode_syntax_context

for_all_ctxts_in 🔒

for_all_expns_in 🔒

raw_encode_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.