:11:1: error: [GHC-36705] • Unsafe overlapping instances for Pos [Int] arising from a use of ‘res’ The matching instance is: instance [overlapping] [safe] Pos [Int] -- Defined at :9:30 It is compiled in a Safe module and as such can only overlap instances from the same module, however it overlaps the following instances from different modules: instance [safe] Pos [a] -- Defined at P13_A.hs:6:10 • In the expression: res [1 :: Int, 2 :: Int] In an equation for ‘it’: it = res [1 :: Int, 2 :: Int]