BadRecordUpdate.elm

type alias HasAnInt = { foo : Int }

badExample : HasAnInt -> HasAnInt
badExample record =
    { record | foo = toString record.foo }

{- Since we're changing the type, we need to give the correct
type annotation for the new return value
-}
thisWorks : HasAnInt -> { foo : String }
thisWorks record =
    { record | foo = toString record.foo }
    
{- We can also give that new return value a type alias so we
can reuse it in other places, too.
-}
type alias HasAString = { foo : String }

thisAlsoWorks : HasAnInt -> HasAString
thisAlsoWorks record =
    { record | foo = toString record.foo }