Refactor of Context instance hierarchy #383
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Odomontois
requested review from
catostrophe,
danslapman,
oskin1 and
Z1kkurat
as code owners
| trait ContextInstances[TC[f[_], r] >: WithContext[f, r]] extends LocalInstances[TC] | ||
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| /** lightweight version of ApplicativeLocal | ||
| * consider to use `WithLocal` or `In` for better type inference |
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| * consider to use `WithLocal` or `In` for better type inference | |
| * consider using `WithLocal` or `In` for better type inference |
BTW, type In[C, F[_]] = WithContext[F, C] doesn't seem to be a proper alternative for Local, does it?
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Yes, an artifact of hasty copypasta
| type HasContext[F[_], C] = Context[F] { type Ctx = C } | ||
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| type HasLocal[F[_], C] = Local[F] { type Ctx = C } | ||
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| type HasProvide[F[_], G[_], C] = Provide[F] { type Ctx = C; type Lower[A] = G[A] } | ||
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| type HasContextRun[F[_], G[_], C] = RunContext[F] { type Ctx = C; type Lower[A] = G[A] } | ||
| type HasContextRun[F[_], G[_], C] = RunContext[F] { type Lower[A] = G[A]; type Ctx = C; } |
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Does this swap affect inference anyhow? Why hasn't HasProvide been changed?
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No, this change is insignificant. Just a scar of searching how to make ReaderT instance work inside ContextBase companion
| @@ -3,13 +3,15 @@ import cats.{ApplicativeError, MonadError} | |||
| import cats.data.Ior | |||
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| package object tofu { | |||
| type In[C, F[_]] = WithContext[F, C] | |||
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Just small type alias to write X In F instead of F WithContext X
| def apply[F[_]](implicit ctx: RunContext[F]): HasContextRun[F, ctx.Lower, ctx.Ctx] = ctx | ||
| type Aux[F[_], G[_], C] = HasContextRun[F, G, C] | ||
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| final implicit def readerTContext[F[_]: Applicative, C]: HasContextRun[ReaderT[F, C, *], F, C] = |
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So we still can't avoid this even with Kai's approach?
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Yes, unfortunately, scala reject to search parent companions for Aux-types with lifted higher-kinded type-members.
So, removing this and Provide's one makes ContextSuite fail
| } | ||
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| /** a mix-in for supplying environment data type companions with useful things */ | ||
| trait Companion[C] { |
Odomontois
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