RFR: 8371248: Crash in -Xdoclint with invalid @link

[Liam Miller-Cushon]

On Wed, 12 Nov 2025 17:26:00 GMT, Jan Lahoda <jlahoda at openjdk.org> wrote:

> The attribution of javadoc links fails with an NPE if the link is like `{@link double.NAN Bad}` - it tries to dereference the `double`, which obviously cannot work.
> 
> This PR mostly just adds checks that will stop the attribution, and return `null`.
> 
> Note that for `{@link double Class}` the existing code does not crash and returns the internal a `TypeElement` corresponding to the `double`. This is a weird quirk of this API, and is preserved with this PR (although a test is added for it into `test/langtools/tools/javac/doctree/ReferenceTest.java`).

test/langtools/tools/javac/doctree/ReferenceTest.java line 90:

> 88:  * {@link double#NAN Bad}
> 89:  * {@link double#double Bad}
> 90:  * {@link java.base/double Bad}

I also some crashes in non-primitive examples like


 * {@link List<String>.of}
 * {@link Optional<String>.empty}
 * {@link Map<String, Integer>.Entry}


This PR also fixes them, but maybe consider adding more tests like that, unless it's already covered?

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PR Review Comment: https://git.openjdk.org/jdk/pull/28272#discussion_r2519258043