Type sometimes not inferred for argument when using --disallow-untyped-calls

The `reveal_type` in the example below produces no output, since the expression is not type checked:

```py
# mypy: disallow-untyped-calls

def f(x):
    pass

y = 1
f(reveal_type(y))  # No output!
```

I think that this may also result in crashes, at least when calculating code stats.