RFR: 8340145: Problem with generic pattern matching results in internal compiler error [v2]

[Aggelos Biboudis]

> In the following code, when calculating recursively the covered binding patterns, the nested case assumed that the direct supertype of `T2` will always be represented by a `ClassSymbol`. This PR intervenes the erasure calculation.
> 
> 
> static <T, T2 extends T> T unwrapOrElse(Option<T2> option, T defaultValue) {
>   return switch (option) {
>      case Option.Some(T2 value) -> value;
>      case Option.None<T2> _ -> defaultValue;
>   };
> }

Aggelos Biboudis has updated the pull request incrementally with one additional commit since the last revision:

  Add test with multiple bounds

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/21606/files
  - new: https://git.openjdk.org/jdk/pull/21606/files/b8f0742f..f9f98886

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=21606&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=21606&range=00-01

  Stats: 18 lines in 1 file changed: 17 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/21606.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21606/head:pull/21606

PR: https://git.openjdk.org/jdk/pull/21606