RFR: 8015831: Add lint check for calling overridable methods from a constructor [v7]

[Maurizio Cimadamore]

On Thu, 12 Jan 2023 17:13:55 GMT, Archie L. Cobbs <duke at openjdk.org> wrote:

>> src/jdk.compiler/share/classes/com/sun/tools/javac/comp/ThisEscapeAnalyzer.java line 411:
>> 
>>> 409:         final boolean referenceExpressionNode;
>>> 410:         switch (tree.getTag()) {
>>> 411:         case CASE:
>> 
>> surprised to see `CASE` here - as that's not an expression
>
> I put it there because of switch expressions and `yeild`... ?

Well, yield can... yield a value - `case` doesn't. So I'm confused. Also because the variable is called `referenceExpressionNode` and `CASE` is not an expression. Can `CASE` leave anything on the stack? YIELD does, but CASE?

>> src/jdk.compiler/share/classes/com/sun/tools/javac/comp/ThisEscapeAnalyzer.java line 454:
>> 
>>> 452: 
>>> 453:             // If the expression type is incompatible with 'this', discard it
>>> 454:             if (type != null && !this.isSubtype(this.targetClass.sym.type, type))
>> 
>> Instead of adding the direct reference, and then having to check if the reference needs to be removed, would it be possible not to add the reference in the first place if the types mismatch?
>
> No because (for example) what if you cast?
> 
> The thing you're casting might be compatible, but after the cast it might become incompatible.

Uhm. Turns out I probably did not understand the filter correctly, and now I'm more dubious about what it actually does. Say you have this hierarchy:


interface A { }
class B {
     B() {
          A a = (A)this;
          ...
      }
 }
 class C extends B implements A { }
 ```

Pathological case, I know. But the filtering will end up dropping the expression Ref on the floor, right? (because B and A are unrelated).

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PR: https://git.openjdk.org/jdk/pull/11874