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

[Archie L. Cobbs]

On Thu, 12 Jan 2023 10:18:27 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

>> Archie L. Cobbs has updated the pull request incrementally with two additional commits since the last revision:
>> 
>>  - Use the more appropriate Type comparison method Types.isSameType().
>>  - Add some more comments to clarify how the analysis works.
>
> src/jdk.compiler/share/classes/com/sun/tools/javac/comp/ThisEscapeAnalyzer.java line 294:
> 
>> 292:                   !(this.currentClass.sym.isSealed() && this.currentClass.permitting.isEmpty()) &&
>> 293:                   !(this.currentClass.sym.owner.kind == MTH) &&
>> 294:                   !this.privateOuter;
> 
> Here, note that is the owner of the current class symbol is a method, that covers anonymous classes too, which is a part of `privateOuter`. So the only think we need to check here is whether "currentClass" is private, which is a simple predicate. No need to carry `privateOuter` I believe

Unless you explicitly declare a nested class `private`, it won't have the `ACC_PRIVATE` flag, even though it is "implicitly private" because it has a `private` enclosing class.

Example:

$ cat PrivateOuter.java 
public class PrivateOuter {
    private static class Inner1 {
        static class Inner2 {
        }
    }
}
$ javap -v PrivateOuter$Inner1$Inner2
Classfile /Users/archie/proj/jdk/flex-test/classes/PrivateOuter$Inner1$Inner2.class
  Last modified Jan 12, 2023; size 408 bytes
  SHA-256 checksum 51ba6d39a5e66df2a078761d6424acbea7a8e32b8451f6ca7d2af49889673b2c
  Compiled from "PrivateOuter.java"
class PrivateOuter$Inner1$Inner2
  minor version: 0
  major version: 63
  flags: (0x0020) ACC_SUPER
  this_class: #7                          // PrivateOuter$Inner1$Inner2
  super_class: #2                         // java/lang/Object
  ...


So we have to keep track of this "implicit privateness" manually, which is what the `privateOuter` flag is for.

-------------

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