RFR: 8372948: Store end positions directly in JCTree [v8]

[Jan Lahoda]

On Mon, 26 Jan 2026 16:42:39 GMT, Liam Miller-Cushon <cushon at openjdk.org> wrote:

>> This change adds a field to `JCTree` to store end positions, instead of using a separate `EndPosTable` map. See also [this compiler-dev@ thread](https://mail.openjdk.org/pipermail/compiler-dev/2025-November/032254.html).
>> 
>> I performed the refactoring in stages, preserving existing semantics at each step.
>> 
>> There are two known places where this changes existing behaviour that are reflected in changes to tests:
>> 
>> * `test/langtools/tools/javac/api/TestJavacTask_Lock.java` - this test asserts that calling `JavacTask#parse` first and then calling `#call` or `#parse` second will fail. The assertion that the test is currently expecting is thrown when the `EndPosTable` gets set a second time, and this change means that no longer results in an exception. If desired `JavacTask#parse` could be updated to explicitly check if it is called twice and fail, instead of indirectly relying on the `EndPosTable` for that.
>> 
>> * `test/langtools/tools/javac/diags/DiagnosticGetEndPosition.java` - there's a comment that 'ideally would be "0", but the positions are not fully set yet', and with the new approach the end position is available to the test, so it resolves the comment. Also the test logic didn't handle platform specific line ending variations correctly, so I updated it to work on windows now that end positions are present.
>
> Liam Miller-Cushon has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Rename mapPos to endpos, there is no longer an end position map

Looks good to me, thanks!

(Please give Maurizio and others some time to add more comments if needed.)

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Marked as reviewed by jlahoda (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/28610#pullrequestreview-3711398649