: abs_ev_vars binds dictionaries from let-bindings
Simon
From: Alejandro Serrano Mena
Sent: 17 January 2020 08:26
To: Simon Peyton Jones
Cc: GHC developers
Subject: Re: Find constraints over type
My goal is to add type information on hover within `ghcide`. Right now, when
you select a variable, we give
My goal is to add type information on hover within `ghcide`. Right now,
when you select a variable, we give back the type as reported in the
corresponding Var. However, when this type involved a type variable, it
misses a lot of important information about the typing context in which we
are
There is definitely no pure way to get from ‘a’ to its constraints.
* It is far from clear what “its constraints” are. Is (C a b) such a
constraint? C [a] b? What about superclasses?
* Constraints vary depending on where you are. GADT matches can bring
into scope extra constraints
Alejandro Serrano Mena writes:
> Dear GHC devs,
> I am trying to figure out a way to obtain the constraints that hold over a
> type. Let me give you an example: suppose that I write the following
> function:
>
> f :: Eq a => [a] -> Bool
> f xs = xs == []
>
> If I ask for the type of the Var '
