T10698.hs:13:29:
    Could not coerce from ‘Map k1 a’ to ‘Map k2 a’
      because the first type argument of ‘Map’ has role Nominal,
      but the arguments ‘k1’ and ‘k2’ differ
      arising from a use of ‘coerce’
    from the context (Coercible k1 k2)
      bound by the RULE "map1/coerce" at T10698.hs:13:1-34
    In the expression: coerce
    When checking the transformation rule "map1/coerce"