I believe the following produces an unexpected behavior:

    from inspect import getsource


    def bar(*funcs):
        def decorator(func):
            return func

        return decorator


    @bar(lambda x: bool(True), lambda x: False)
    async def foo():
        ...


    print(getsource(foo))

The output shows only the decorator declaration and none of the function:

    @bar(lambda x: bool(True), lambda x: False)


From my investigation, it seems like this requires the following conditions to be true:
- lambdas are passed in decorator arguments
- there is more than one lambda
- at least one of the lambdas has a function call

Passing the lambdas as default function arguments seems okay:

    async def foo(bar=[lambda x: bool(True), lambda x: False]):
        ...

A single lambda seems okay:

    @bar(lambda x: bool(True))
    async def foo():
        ...

Lambdas with no function calls also seem okay:

    @bar(lambda x: not x, lambda: True)
    async def foo():
        ...

Tested this on:
- Python 3.10.2
- Python 3.9.9
- Python 3.8.11
- Python 3.7.12

I'm removing 3.7 and 3.8 from the "versions" field, since they're currently only accepting patches for security-related bugs. But thanks for testing on those versions as well — that's useful information!

Sorry about that. I am doing some more digging to see if I can find the route of it and a proposal for a non-breaking patch. The problem seems to be in BlockFinder.tokeneater.

Duplicate of https://bugs.python.org/issue38854

Sorry I didn't come across our before submitting.