compiler/basicTypes/IdInfo.hs¶
Note [Specialisations and RULES in IdInfo]¶
Generally speaking, a GlobalId has an empty RuleInfo. All their RULES are contained in the globally-built rule-base. In principle, one could attach the to M.f the RULES for M.f that are defined in M. But we don’t do that for instance declarations and so we just treat them all uniformly.
The EXCEPTION is PrimOpIds, which do have rules in their IdInfo. That is jsut for convenience really.
However, LocalIds may have non-empty RuleInfo. We treat them differently because:
- they might be nested, in which case a global table won’t work
- the RULE might mention free variables, which we use to keep things alive
In TidyPgm, when the LocalId becomes a GlobalId, its RULES are stripped off and put in the global list.
Note [Levity info]¶
Ids store whether or not they can be levity-polymorphic at any amount of saturation. This is helpful in optimizing the levity-polymorphism check done in the desugarer, where we can usually learn that something is not levity-polymorphic without actually figuring out its type. See isExprLevPoly in CoreUtils for where this info is used. Storing this is required to prevent perf/compiler/T5631 from blowing up.
See Note [Levity info]
