RFR: 8272564: Incorrect attribution of method invocations of Object methods on interfaces [v3]

[Jan Lahoda]

> Consider these declarations:
> 
>     interface I {
>         public String toString();
>     }
>     interface J extends I {}
> 
> 
> There are two issues with the `toString` inherited from `I` into `J`:
> -`Trees.isAccessible(..., I.toString, J)` will return false, because `Resolve.isAccessible` will return false, because `Resolve.notOverriddenIn` returns false, because the `Object.toString` method is found as an implementation of `I.toString` in the context of `J`. This is unfortunate, because `Elements.getAllMembers(J)` will return `I.toString` as a member, not `Object.toString`, so any API client listing all members and then validating them using `Trees.isAccessible` will filter `toString` out. The proposed solution is to avoid using the methods from `java.lang.Object` as implementations of interface methods in `Resolve.notOverriddenIn`. (Interfaces don't inherit from `j.l.Object` per my understanding of JLS.)
> -as a slightly less problematic case, consider:
> 
> I i = null;
> i.toString(); //AST and classfile contain call to I.toString()
> J j = null;
> j.toString(); //AST and classfile contain call to j.l.Object.toString()
> 
> 
> I believe the second invocation should also preferably be a call to `I.toString()`, not a call to `j.l.Object.toString()`. The reason for this behavior is that in javac, interfaces have `j.l.Object` as a supertype, so method lookups over interfaces will look into `j.l.Object` before looking into the superinterfaces, and the concrete method will prevail over the super interface method found later. The proposal is, for interfaces, to only look into `j.l.Object` is a method is not found in the interface and its superinterfaces.

Jan Lahoda has updated the pull request incrementally with one additional commit since the last revision:

  Reflecting review comments.

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/5165/files
  - new: https://git.openjdk.java.net/jdk/pull/5165/files/9ea15dcc..16ed87f3

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=5165&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=5165&range=01-02

  Stats: 13 lines in 3 files changed: 11 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5165.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5165/head:pull/5165

PR: https://git.openjdk.java.net/jdk/pull/5165