Error cascade when unrelated class derivation fails
Pretty minor bug, but I thought I'd point it out:
module A where import Data.Typeable data A = A deriving (Show, Typeable) data B = B A deriving (Show)
I get two errors when I expect one:
A.hs:3:28: Can't make a derived instance of `Typeable A': You need -XDeriveDataTypeable to derive an instance for this class In the data declaration for `A' A.hs:4:24: No instance for (Show A) arising from the 'deriving' clause of a data type declaration Possible fix: add an instance declaration for (Show A) or use a standalone 'deriving instance' declaration, so you can specify the instance context yourself When deriving the instance for (Show B)
The failed Typeable derivation also causes the Show derivation to fail, which causes an error later in the file.
|Component||Compiler (Type checker)|