Hide the gnarly levity polymorphism stuff in the signatures of `undefined`, `throw`, etc
In base-4.12, throw goes from
throw :: Exception e => e -> ato
throw :: forall (r :: RuntimeRep). forall (a :: TYPE r). forall e. Exception e => e -> a http://hackage.haskell.org/package/base-4.12.0.0/docs/Control-Exception-Base.html#v:throw
Similar story for undefined. Even as a fairly experienced haskell programmer I find the signature difficult to parse, leaving aside the meaning of RuntimeRep and TYPE. The amount of research an expert in Haskell 98 would have to do to thoroughly understand that signature is unreasonable (the various meanings of forall, DataKinds, as well as the levity polymorphism stuff).
I don't have a proposed solution, but a constraint synonym or something that hid RuntimeRep and TYPE, and which could be documented with "This means a type with any runtime representation; everything is fine" would be okay.
Relevant: #12030 (closed) #11549 (closed)
Trac metadata
| Trac field | Value |
|---|---|
| Version | 8.6.3 |
| Type | FeatureRequest |
| TypeOfFailure | OtherFailure |
| Priority | normal |
| Resolution | Unresolved |
| Component | libraries/base |
| Test case | |
| Differential revisions | |
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| Blocking | |
| CC | |
| Operating system | |
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