T15692.hs:9:18: warning: [-Wdeferred-type-errors (in -Wdefault)]
    • Couldn't match expected type ‘F (f x)’ with actual type ‘Bool’
    • In the pattern: False
      In the pattern: FS False
      In the declaration for pattern synonym ‘FS'’

T15692.hs:9:18: warning: [-Wdeferred-type-errors (in -Wdefault)]
    • Couldn't match expected type ‘F (f0 x)’ with actual type ‘Bool’
    • In the first argument of ‘FS’, namely ‘False’
      In the expression: FS False
      In an equation for ‘FS'’: FS' = FS False
    • Relevant bindings include $bFS' :: F x (bound at T15692.hs:9:9)