typing.TYPE_CHECKING not true during dev

Seems like typing.TYPE_CHECKING is not true during dev.
e.g.:
```py
from typing import TYPE_CHECKING:
if TYPE_CHECKING:
from somewhere import MyClass

async def myFunction(x:str, a:int, c:"MyClass"):
c.someva # no auto-complete or suggestion here

```

if line 2 is `if TYPE_CHECKING or True`
code will be suggested and autocompleted.
based on typing.py L1444:
```py
# Constant that's True when type checking, but False here.
TYPE_CHECKING = False
```
OS Ubuntu 18.04.2 LTS
Python 3.7.1

Am i missing something, or wrong configuration?