Documentation

IntMap key for a binder (uniques are 64-bit as of GHC 9.10; low bits suffice as map keys within one compilation).

In the RWC.Primitives module (the GHC-visible mirror of PrimBasis), type and constructor names map to their bare occurrence names.

Home modules (loaded from source) get qualified names; known external entities are in the tables; anything else external is out of vocabulary. There is no unit map here, so approximate: well-known external namespace prefixes are rejected, everything else is assumed to be a home module.

Eidos names for constructors.

Split a qualified start symbol ("Main.start") into module and occurrence parts.

The display occurrence for a local binder: real source names pass through; GHC-machine names (system names, plus the desugarer's ds/wild/eta family by occurrence shape -- isSystemName alone misses some) get the compiler-owned $ prefix, so downstream naming policy knows they are free to rename, merge, or discard rather than worth preserving as signal names. The shape check defers to a real source span: a user's own binder named eta or ds keeps its name. Advisory only: uniqueness never depends on the marker.

Arguments the translation erases: types, coercions, and evidence -- except evidence for user classes, which is kept as ordinary data (dictionaries as values; specialization plus the partial evaluator's dictionary-let substitution and case-of-known-constructor eliminate them).

Evidence to erase: everything but user-class dictionaries.

Is this a user-class predicate type -- or evidence for one under quantifiers and a context (an instance's dfun type)? A class defined in a home module (approximated by defining-module namespace, like the tycon table's fallback): built-in evidence (KnownNat, Monad, HasCallStack, ...) is external and erased; classes in the user's own modules are data, and their dfuns -- contexted instances included -- are ordinary definitions.

Key for the external tycon table: defining module and occurrence.

External tycons mapped by (defining module, occurrence) to (Eidos name, number of leading type args to drop).

Base combinators supported via synthesized (INLINE) Eidos definitions (see bridgeBaseVocab in ReWire.GHC.ToEidos); outer key: defining module; inner: occurrence -> Eidos name.