Jaro

Perhaps "placeholder" is a more intuitive name for "unification variable"? I think it captures the intuition that the placeholder can still be assigned any other type.

Related to "rigid" type variables specifically, here is another program that produces an error message containing that word: ``` module Bar where f :: a -> a -> () f...

Also in the case of non-literals the wording of the current error message suggest that an instance should be defined, but I think that there are many cases, probably even...

@ByteEater-pl how do your feel about the suggestion I added to my comment: Perhaps you want to define an instance of ‘Num‘ for the type ‘String‘ That can also be...

See [the documentation of `TypeApplications`](https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/exts/type_applications.html#extension-TypeApplications): > [Type applications] can be used whenever the full polymorphic type of the function is known. If the function is an identifier (the common case),...

I think what is happening is that like this: ```haskell -- due to the 0 pattern match leftSkewed :: (Eq a, Num a) => a -> b -- due to...

benchmark | old time | old unit | old deviation | new time | new unit | new deviation | change -- | -- | -- | -- | --...

I'm in favor of both `dup` and `arr2` in `Control.Arrow` if it does not break too much existing code. In particular, I think the name `arr2` is intuitive for a...

All failures in the jobs of e651d41 seem to be spurious (except for the stylish-haskell formatting failure).

I think the remaining failures are not caused by this PR. Are these kinds of spurious failures common in HLS? Also, I would really like to get this merged before...