Backport "Fix generic signatures for mixin forwarders conflicting type parameter names" to 3.8.0 #24622
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…r names Fixes #24134 f99dba2 started emitting Java generic signature for mixin forwarders. However, when generating Java generic signatures for mixin forwarders, method-level type parameters could shadow class-level type parameters with the same name. For example, when `JavaPartialFunction[A, B]` implements `PartialFunction1[A, B]`, ```scala trait Function1[-T1, +R]: def compose[A](g: A => T1): A => R = ??? trait PartialFunction[-A, +B] extends Function1[A, B]: def compose[R](k: PartialFunction[R, A]): PartialFunction[R, B] = ??? abstract class JavaPartialFunction[A, B] extends PartialFunction[A, B] ``` the generated mixin forwarder for `compose` in Function1 was like: ```java public abstract class JavaPartialFunction<A, B> implements scala.PartialFunction<A, B> { public <A> scala.Function1<A, B> compose(scala.Function1<A, A>); ``` which is obviously incorrect, the type parameter `A` of `compose[A]` is shadowed by the `A` in `JavaPartialFunction<A, B>`. The `compose`'s type parameter should use an unique name like: ```java public abstract class JavaPartialFunction<A, B> implements scala.PartialFunction<A, B> { public <T> scala.Function1<T, B> compose(scala.Function1<T, A>); ``` This commit fix the problem by - Tracks class-level type parameter names when generating method signatures - Renames conflicting method-level type parameters (A → A1, A2, etc.) [Cherry-picked 4e284c5]
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Backports #24567 to the 3.8.0-RC3.
PR submitted by the release tooling.