Modulepolysemy-plugin-0.4.5.2Haskell2010

Polysemy.Plugin.Fundep.Unification

3 types
4 values

Packagepolysemy-plugin-0.4.5.2
Exports7
LanguageHaskell2010
LicenceBSD-3-Clause
SourceUnification.hs

datadata SolveContext

The context in which we're attempting to solve a constraint.

Constructors

FunctionDef (Set TyVar)
In the context of a function definition. The Set TyVar is all of the skolems that exist in the [G] constraints for this function.
InterpreterUse Bool (Set TyVar)
In the context of running an interpreter. The Bool corresponds to whether we are only trying to solve a single Member constraint right now. If so, we *must* produce a unification wanted.

Instances3Eq, Ord, Outputable

Eq SolveContextDefined in polysemy-plugin-0.4.5.2 · Polysemy.Plugin.Fundep.Unification
Ord SolveContextDefined in polysemy-plugin-0.4.5.2 · Polysemy.Plugin.Fundep.Unification
Outputable SolveContextDefined in polysemy-plugin-0.4.5.2 · Polysemy.Plugin.Fundep.Unification

valuemustUnify :: SolveContext -> Bool

Depending on the context in which we're solving a constraint, we may or may not want to force a unification of effects. For example, when defining user code whose type is Member (State Int) r => ..., if we see get :: Sem r s, we should unify s ~ Int.

valueunify

:: SolveContext
-> Type
wanted
-> Type
given
-> Maybe Subst

Determine whether or not two effects are unifiable.

All free variables in [W] constraints are considered skolems, and thus are not allowed to unify with anything but themselves. This properly handles all cases in which we are unifying ambiguous [W] constraints (which are true type variables) against [G] constraints.

valuetryUnifyUnivarsButNotSkolems :: Set TyVar -> Type -> Type -> Maybe Subst

datadata Unification

A wrapper for two types that we want to say have been unified.

Constructors

Unification
- _unifyLHS :: OrdType
- _unifyRHS :: OrdType

Instances2Eq, Ord

Eq UnificationDefined in polysemy-plugin-0.4.5.2 · Polysemy.Plugin.Fundep.Unification
Ord UnificationDefined in polysemy-plugin-0.4.5.2 · Polysemy.Plugin.Fundep.Unification

newtypenewtype OrdType

Types don't have Eq or Ord instances by default, even though there are functions in GHC that implement these operations. This newtype gives us those instances.

Constructors

OrdType
- getOrdType :: Type

Instances2Eq, Ord

Eq OrdTypeDefined in polysemy-plugin-0.4.5.2 · Polysemy.Plugin.Fundep.Unification
Ord OrdTypeDefined in polysemy-plugin-0.4.5.2 · Polysemy.Plugin.Fundep.Unification

valueunzipNewWanteds

:: Set Unification
-> [(Unification, Ct)]
-> ([Unification], [Ct])

Filter out the unifications we've already emitted, and then give back the things we should put into the S.Set Unification, and the new constraints we should emit.