ghc-4.02: Class 'Functor' does not have a method 'map'

[Joachim Schmid]

I'am using cygwin b20.1 and the binary distribution ghc-4.02 for Windows
NT.

Compiling the program

module Main where

data D a = D a

instance Functor D where
  map f (D a) = D (f a)

main :: IO ()
main = return ()

leads to the strange error

> Main.hs:6
>     Warning: No explicit method nor default method for 'fmap'
>              in an instance declaration for 'Functor'
>
> Main.hs:6: Class 'Functor' does not have a method 'map'

Has anybody renamed 'map' to 'fmap'?