Python 3.7: dataclass does not raise `TypeError` for `eq=False`

When you don't define __eq__, __eq__ will resolve to object.__eq__. That is what's happening when you create a dataclass with eq=False.

object.__eq__(self, other) is False unless self is other, i.e. unless the two are the same object.

In python3.7, given the following dataclass definition

@dataclass(eq=False)
class Number:
    val: int

the expected result for Number(1) == Number(1) is False. This is correct since setting eq = True only overrides the default python-object equality function, which just checks for identical references (same as Number(1) is Number(1), which might more obviously evaluate to false) in this case.

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The dataclass specification is a bit lacking here. It explains the eq parameter with

eq: If true (the default), an __eq__ method will be generated. This method compares the class as if it were a tuple of its fields, in order. [...]

but in order to understand the issue you ran into, you also need to know that the basic python object already comes with an __eq__ function:

>>> class A: pass
...
>>> dir(A())
['__class__', '__delattr__', ... '__eq__', ...]  # has __eq__ already