Parse error when no space between keyword and float

```python
handcrafted = [
# looks like an attribute lookup, actually keyword + float
'_ in.0',
'while.0:_',
'_ if _ else.0',
]
for s in handcrafted:
assert compiles(s), repr(s)
assert not libcst_native_parses(s), repr(s)
```

_Originally posted by @Zac-HD in https://github.com/Instagram/LibCST/issues/930#issuecomment-1581965630_