The most common error is missing keyword "await" in function call. "f()" instead of "await f()".

There is a way to detect this error at runtime with minimal false positive and with minimal overhead. We can add a new opcode which checks if the value on the top of the stack is awaitable and raise warning/error in that case, and add it after every functional call whose result is ignored in asynchronous functions. It could even be merged with POP_TOP to reduce overhead.

    CALL_FUNCTION ...
    WARN_IF_AWAITABLE_AND_POP_TOP