RFR: 8325088: Overloads that differ in type parameters may be lost

[Pavel Rappo]

On Wed, 27 Mar 2024 17:19:35 GMT, Pavel Rappo <prappo at openjdk.org> wrote:

> Creating a link to a constructor or a method or comparing constructors or methods __does not__ factor in type parameters. When constructors or methods are overloaded and differ only in type parameters -- a situation which is absent in JDK API, but present elsewhere -- that causes significant defects, such as:
> 
>   - missing entries in summary tables, lists and indexes,
>   - duplicating links in the table of contents.
> 
> This PR fixes those defects, and the fix is two-fold. Firstly, we update comparators to consider type parameters. That takes care of missing constructors and methods. Secondly, we update id (anchor) and link generation to always use the "erased" notation. That takes care of duplicating links.
> 
> What's the "erased" notation? Suppose we have the following method:
> 
>     <T extends String> T m(T arg)
> 
> The current notation refers to it as `m(T)`. That works fine until there's no other method, such as
> 
>     <T> T m(T arg)
> 
> In which case, the current notation will produce a collision: `m(T)`. By contrast, the erased notation for those two methods is `m(java.lang.String)` and `m(java.lang.Object)` respectively. No collision.
> 
> While longer, I believe that the erased notation is collision-proof. Why? Because [JLS 8.4.2][] says that "it is a compile-time error to declare two methods with override-equivalent signatures in a class". Which means that for any two constructors or methods the erasure of their signatures must differ, or else it won't compile.
> 
> The change is pretty straightforward, except for some test fallout that required attention.
> 
> [JLS 8.4.2]: https://docs.oracle.com/javase/specs/jls/se22/html/jls-8.html#jls-8.4.2

While I've been working with javadoc for the last five years, somehow I've never had to deal with composability functionality provided by `link` and `linkoffline`. These options have been there since at least 1998: the earliest bug I found to mention them is https://bugs.openjdk.org/browse/JDK-4065454. Wow.

Back to the compatibility problem at hand. So we want to be able to link from the new output to the old output. Linking from the old output to the new output is out of the question, I suppose. After examining `Extern` briefly, I agree with Jon, in that the problem is not about transforming one string into another, but about mapping an element to a string.

I'll see what I can minimally do to support that.

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PR Comment: https://git.openjdk.org/jdk/pull/18519#issuecomment-2025117217