textField
  :: ( Monad m
     , RenderMessage (HandlerSite m) FormMessage
     )
  => Field m Text
textField = I.textField
    { fieldView = fieldView I.textField
    }

Foo.hs:37:19: error:
    • Couldn't match type ‘HandlerSite m0’ with ‘HandlerSite m’
      Expected type: FieldViewFunc m Text
        Actual type: FieldViewFunc m0 Text
      NB: ‘HandlerSite’ is a type function, and may not be injective
      The type variable ‘m0’ is ambiguous
    • In the ‘fieldView’ field of a record
      In the expression: I.textField {fieldView = fieldView I.textField}
      In an equation for ‘textField’:
          textField = I.textField {fieldView = fieldView I.textField}
    • Relevant bindings include
        textField :: Field m Text
          (bound at Foo.hs:36:1)

textField
  :: ( Monad m
     , RenderMessage (HandlerSite m) FormMessage
     )
  => Field m Text
textField = f
    { fieldView = fieldView
    }
  where
    f@Field {..} = I.textField