lahodaj opened a new pull request, #9450:
URL: https://github.com/apache/netbeans/pull/9450
There's a `null` checker in `java/java.hints`, `NPECheck`. I am considering
some updates to it, and, as a preparation for that, I was looking at the
current `State`s there. There are some weird ones:
- `NULL_HYPOTHETICAL` and `NOT_NULL_HYPOTHETICAL` - these are meant to cover
cases like:
```
boolean b = o != null && /*we know o is non-`null` here, marked as
`NOT_NULL_HYPOTHETICAL`*/ ...;
//we can't really say much about `o` here, except that we tested it for
`null`
```
the hypothetical states were basically used as "transient state" in
expressions. I think that with the experience from pattern matching, this is
overly complex: I think we can simply keep ordinary `NULL`/`NOT_NULL` states,
but keep them "when true" and "when false", and then use and merge them
accordingly. This also avoids the need to run conditions twice (once for
ordinary run, and once for a negated one). Overall, this should make stuff
simpler.
- `INSTANCE_OF_FALSE` and `INSTANCE_OF_TRUE`. I think the only real thing
this was doing is code along these lines (or conversely the same with an `if`):
```
class Test {
public void test(Object o) {
boolean b = !(o instanceof Integer) && o./*warning here,
dereferencing possible null*/toString() != null;
}
}
```
Normally, the NPECheck recognizes several "possible nulls", in particular
`POSSIBLE_NULL`, which does not produce any warning, and
`POSSIBLE_NULL_REPORT`, which is used if there's a confirmation the variable
might be null, like if there's a test for null for the variable, and which
produces the "possibly dereferencing null` warning. The instanceof states are
used to make the `instanceof` work as a test for null, but, frankly, it is not:
we have no firm idea whether `o` can or cannot be `null` if the `instanceof`
fails. I.e. the behavior of `POSSIBLE_NULL` is more in order here, not the
`POSSIBLE_NULL_REPORT`. So, this PR is stripping the instanceof states, and
won't produce a warning in the above case.
---
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