T15558.hs:11:15: warning: [GHC-40564] [-Winaccessible-code (in -Wdefault)]
    • Inaccessible code in
        a type expected by the context:
          (a ~ Bool) => ()
      Couldn't match type ‘Int’ with ‘Bool’
    • In the first argument of ‘MkFoo’, namely ‘()’
      In the expression: MkFoo ()
      In an equation for ‘f’: f MkT = MkFoo ()