The latest available GHC distribution that can be selected in circle.yml is 7.10.2, which is now more than 18 months old.
There have been three major releases since then, 7.10.3, 8.0.1, and 8.0.2, with the first two now more than 6 months old. If Haskell is going to be presented as a first-class language in CirceCI, it would seem that an update every 6 months to keep current isn’t too much to ask.
This is particularly inconvenient because many projects are no doubt using
stack to acquire the right GHC version, but
stack is first packaged with GHC 7.10.3. See Install Stack by default.