[Python] All Union cases across all union types return the same Hash Code

[HLWeil]

Description

For union cases always the same hash value 2654435761 is returned.

Repro code

test.fsx

type X =
    | A of int
    | B of string

let x = A 1
let y = B "hello"

x.GetHashCode() = y.GetHashCode

test.cmd

dotnet fable . --lang python
python test.py

Expected and actual results

Expected result: false

Actual result: true

Debugging

In python, the function safe_hash is called on the object
-> this calls number-hash on the result of ObjectRef.id

ObjectRef.id always returns 1, so the resulting hash of safe_hash is always 2654435761

For reference, this is the source code in util.py

class ObjectRef:
    id_map: dict[int, int] = dict()
    count = 0

    @staticmethod
    def id(o: Any) -> int:
        _id = id(o)
        if _id not in ObjectRef.id_map:
            count = ObjectRef.count + 1
            ObjectRef.id_map[_id] = count

        return ObjectRef.id_map[_id]


def safe_hash(x: Any) -> int:
    return 0 if x is None else x.GetHashCode() if is_hashable(x) else number_hash(ObjectRef.id(x))


def string_hash(s: str) -> int:
    h = 5381
    for c in s:
        h = (h * 33) ^ ord(c)

    return h


def number_hash(x: int) -> int:
    return x * 2654435761 | 0

Related information

• dotnet fable --version: 4.5.0
• dotnet tool list/update/install: 4.6.0
• Windows11

@Freymaurer