Iterate for NonEmptyList behaves strange

[Masynchin]

Code

import Prelude
import Data.List.Types (NonEmptyList)
import Data.List.Lazy.NonEmpty (iterate)

type Item = { key :: Boolean }

iterateItems :: NonEmptyList Item
iterateItems = iterate stable { key: true }

stable :: forall a. a -> a
stable x = x

Current Behavior

Compiler raises this error about iterateItems:

Could not match type

    NonEmptyList

  with type

    NonEmptyList


while trying to match type NonEmptyList t0
  with type NonEmptyList
              { key :: Boolean
              }
while checking that expression (iterate stable) { key: true
                                                }
  has type NonEmptyList
             { key :: Boolean
             }
in value declaration iterateItems

where t0 is an unknown type
PureScript(TypesDoNotUnify)
No quick fixes available

Expected Behavior

Compiler not raises any errors.

Libs

• PureScript: 0.15.2
• PureScript-Lists: 7.0.0

[Masynchin]

Same with repeat:

infiniteNums :: NonEmptyList Int
infiniteNums = repeat 1

For this code compiler raises:

Could not match type

    NonEmptyList

  with type

    NonEmptyList


while trying to match type NonEmptyList t0
  with type NonEmptyList Int
while checking that expression repeat 1
  has type NonEmptyList Int
in value declaration infiniteNums

[garyb]

You've imported the non-lazy NonEmptyList type here, hence the mismatch. There's an issue in the compiler repo (and a PR has recently been opened) that should help with these cases by qualifying type names.

[Masynchin]

Thanks for explaining difference. I came to this issue trying power NEL, but since it is not Monoid, I can't do it this way. I thought I can replace it with repeat/iterate identity + take, but there is no take for this lazy NEL. You solved my issue, this is just background for issue.

[Masynchin]

I just found this function which do want I want.