EmptyCase004.hs:15:6: warning: [-Wincomplete-patterns (in -Wextra)]
    Pattern match(es) are non-exhaustive
    In a case alternative: Patterns not matched: A2

EmptyCase004.hs:19:6: warning: [-Wincomplete-patterns (in -Wextra)]
    Pattern match(es) are non-exhaustive
    In a case alternative:
        Patterns not matched:
            A1
            A2

EmptyCase004.hs:31:8: warning: [-Wincomplete-patterns (in -Wextra)]
    Pattern match(es) are non-exhaustive
    In a case alternative: Patterns not matched: B1 _

EmptyCase004.hs:35:6: warning: [-Wincomplete-patterns (in -Wextra)]
    Pattern match(es) are non-exhaustive
    In a case alternative:
        Patterns not matched:
            B1 _
            B2

EmptyCase004.hs:47:6: warning: [-Wincomplete-patterns (in -Wextra)]
    Pattern match(es) are non-exhaustive
    In a case alternative:
        Patterns not matched:
            A1
            A2

EmptyCase004.hs:50:9: warning: [-Wincomplete-patterns (in -Wextra)]
    Pattern match(es) are non-exhaustive
    In a case alternative: Patterns not matched: B2

EmptyCase004.hs:51:9: warning: [-Wincomplete-patterns (in -Wextra)]
    Pattern match(es) are non-exhaustive
    In a case alternative: Patterns not matched: B1 _