module Main where
 
main :: IO ()
main = print (read "123")

app\Main.hs:4:15: error:
    * Ambiguous type variable `a0' arising from a use of `read'
      prevents the constraint `(Read a0)' from being solved.
      Probable fix: use a type annotation to specify what `a0' should be.
      These potential instances exist:
        instance Read Ordering -- Defined in `GHC.Read'
        instance Read Integer -- Defined in `GHC.Read'
        instance Read a => Read (Maybe a) -- Defined in `GHC.Read'
        ...plus 22 others
        ...plus 12 instances involving out-of-scope types
        (use -fprint-potential-instances to see them all)
    * In the first argument of `print', namely `(read "123")'
      In the expression: print (read "123")
      In an equation for `main': main = print (read "123")
  |
4 | main = print (read "123")
  |               ^^^^^^^^^^

module Main where
 
main :: IO ()
main = print ((read "123") :: Integer)

{-# LANGUAGE TypeApplications  #-}
 
module Main where
 
main :: IO ()
main = print (read @Integer "123")