panic! (the 'impossible' happened)
(GHC version 8.0.2 for x86_64-apple-darwin):
initTc: unsolved constraints
WC {wc_insol = [W] action_a1Ei :: t_a1Eh[tau:1] (CHoleCan: action)}
Code:
import Data.Char
import Data.List
data InvoiceStruct = InvoiceStruct
{ total :: Int
, shippedItemCount :: Int
} deriving (Show)
invoice :: InvoiceStruct -> String -> Int -> InvoiceStruct
invoice i comp val = (action) i[total] val