T9739.hs:4:1: error: [GHC-29210]
    • Superclass cycle for ‘Class1’
        one of whose superclasses is ‘Class3’
        one of whose superclasses is ‘Class1’
    • In the class declaration for ‘Class1’
    Suggested fix: Perhaps you intended to use UndecidableSuperClasses

T9739.hs:9:1: error: [GHC-29210]
    • Superclass cycle for ‘Class3’
        one of whose superclasses is ‘Class1’
        one of whose superclasses is ‘Class3’
    • In the class declaration for ‘Class3’
    Suggested fix: Perhaps you intended to use UndecidableSuperClasses