T18648.hs:6:4: error:
    • Illegal argument ‘f a’ in:
        ‘type Bar1 (f a) = ...’
        The arguments to ‘Bar1’ must all be distinct type variables
    • In the default type instance declaration for ‘Bar1’
      In the class declaration for ‘Foo1’

T18648.hs:10:4: error:
    • Illegal argument ‘Bar2 a’ in:
        ‘type Bar2 (Bar2 a) = ...’
        The arguments to ‘Bar2’ must all be distinct type variables
    • In the default type instance declaration for ‘Bar2’
      In the class declaration for ‘Foo2’