writeFastMutInt (FastMutInt arr) (I# i) = IO $ \s ->
  case writeIntArray# arr 0# i s of { s ->
  (# s, () #) }
writeFastMutInt (FastMutInt arr) (I# i) = IO $ \s ->
  case writeIntArray# arr 0# i s of { s ->
  (# s, () #) }
writeFastMutInt (FastMutInt arr) (I# i) = IO $ \s ->
  case writeIntArray# arr 0# i s of { s ->
  (# s, () #) }