ExpandSynsFail2.hs:19:37: error:
    • Couldn't match type ‘Bool’ with ‘Int’
      Expected: ST s Foo
        Actual: MyBarST s
      Type synonyms expanded:
      Expected type: ST s Int
        Actual type: ST s Bool
    • In the first argument of ‘runST’, namely ‘barGen’
      In the second argument of ‘(==)’, namely ‘runST barGen’
      In the first argument of ‘print’, namely
        ‘(runST fooGen == runST barGen)’