T14880-2.hs:13:12: warning: [-Wpartial-type-signatures (in -Wdefault)]
    • Found type wildcard ‘_’ standing for ‘Proxy (Foo arg)’
      Where: ‘arg’ is a rigid type variable bound by
               the type signature for:
                 quux :: forall arg. Proxy (Foo arg) -> ()
               at T14880-2.hs:12:1-41
    • In a pattern type signature: _
      In the pattern: _ :: _
      In an equation for ‘quux’: quux (_ :: _) = ()
    • Relevant bindings include
        quux :: Proxy (Foo arg) -> () (bound at T14880-2.hs:13:1)