`&&` is not short-circuiting

The following fails, even though it shouldn't
```go
type X int

requires x != nil
func (x *X)test() bool

func clientX1(x *X) {
    if x != nil && x.test() {

    }
}
```

Error:
```
[info] Precondition of call x.test() might not hold. 
[info] Assertion x != nil might not hold.
```

Dually, it is likely that `||` is also not short-circuiting, although I haven't tested it.