False positive `invalid-inheritance`: diamond inheritance resolves same `Base[int]` to different union orderings

[anci3ntr0ck]

Describe the Bug

Minimal case

class Field[I, M]:
    pass


class Base[I](Field[list[I] | I, I]): # scapy.fields._EnumField
    pass


class Mid[MidI](Base[MidI]): # scapy.fields.EnumField
    pass


class Left(Mid[int]): # scapy.fields.BytesEnumField
    pass


class Mixin[I](Mid[I]):
    pass


class Combined(Mixin[int], Left):  # ERROR Class `Combined` has inconsistent type arguments for base class `Field`: `Field[list[int] | int, int]` and `Field[int | list[int], int]` [invalid-inheritance]
    pass

Expected output

No error. Both branches bottom out in the same substitution Base[int] → Field[list[int] | int, int].

Key observations

Flip the declared union order to Field[I | list[I], I] → the reported pair stays list[int] | int vs int | list[int]. The ordering is produced by resolution, not read from source.

Sandbox Link

https://pyrefly.org/sandbox/?project=v2.hVXLboMwEPwVq1zoofjOMVUrIbVVLz0RVDnBSVYqdoRNBar67xmv8xAJSQ5IgHZnzDIzey0yo1Veg7PLAtFQjYZ2MtNMOV0WVRor2W1FBa2ip6gec5EIt1TbIeOMcNn3i-karp2Ge6e6xAVABubbS5Q7IG965dOABDlMdM8GzObuOXoy4bsCTDjCdNmzbRZkdI2yUB_4sB1AD1bQkoF5qH4is8EyYa-N9NN5-nFx3on4wgP54Wh_JuI8sG2jsAq6ZqHbtM8BG7MEfj2INFp1NX_44Kpc_PX_e5mciTQRn_GF2P9vxDPUve6wBMCazU2C_Ndi4_3W5VIe2m27ltrI2i6dHHXIcEChfhXxahnDCcumcoC94Y6bCt0B

(Only applicable for extension issues) IDE Information

No response