Forbid coroutines usage as boolean conditions

[butvinm]

Rule request:

Restrict usage of coroutines (initialized, but not awaited) as boolean conditions

Thesis

Example:

async def some_coro() -> bool:
    return True

if some_coro(): # The rule should fail at this line
    pass

#  Also, it should work with variable declaration
supposed_boolean = some_coro()
if supposed_boolean: # The rule should fail at this line
    pass

If you use class-based awaitable with an overloaded __bool__ method and want to check its actual condition, you can use the following construction:

class MyCoro:
    def __await__():
        pass

    def __bool___():
         return True

coro_condition = bool(MyCoro()) # The rule is passed

Reasoning

This rule aims to prevent common errors that may occur due to overlooking the await keyword before using coroutines in if statements.

linters and type checkers do not consider the usage of coroutines in if statements as an error since any type can be treated as a boolean, leading to subtle bugs.