Constructor fields in Haskell - see https://www.haskell.org/tutorial/moretypes.html, section 6.2 Field Labels

FieldLabels.hs

Prelude> data Point = Point {x :: Int} deriving Show

Prelude> Point 1
                   Point {x = 1}

Prelude> :t x
                   x :: Point -> Int

Prelude> :t Point
                   Point :: Int -> Point

Prelude> let p = Point 2

Prelude> x p
                   2

The field names can be used as selector functions to extract a component from a structure. In this simple case, with just one parameter, the accessor x is the inverse of the data Constructor Point.