Prelude> :set -XRecordWildCards
Prelude> data Test = Test { t1 :: Int, t2 :: Int } deriving Show
Prelude> t1 = 2
Prelude> Test { t2 = 2, ..}

<interactive>:15:1: warning: [-Wmissing-fields]
    • Fields of 'Test' not initialised: t1
    • In the expression: Test {t2 = 2, ..}
      In an equation for 'it': it = Test {t2 = 2, ..}

<interactive>:15:1: warning: [-Wmissing-fields]
    • Fields of 'Test' not initialised: t1
    • In the expression: Test {t2 = 2, ..}
      In an equation for 'it': it = Test {t2 = 2, ..}
Test {t1 = *** Exception: <interactive>:15:1-18: Missing field in record construction t1

I would expect above to return Test {t1 = 2, t2 = 2} instead of throwing an error.