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

[Vicente Romero]

On Mon, 21 Oct 2024 12:01:11 GMT, Aggelos Biboudis <abimpoudis at openjdk.org> wrote:

> 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;
>   };
> }

src/jdk.compiler/share/classes/com/sun/tools/javac/comp/Flow.java line 913:

> 911: 
> 912:                     for (Type sup : types.directSupertypes(bpOne.type)) {
> 913:                         ClassSymbol clazz = (ClassSymbol) types.erasure(sup).tsym;

general comment: I think that erasure should happen in the desugaring phase, we are already doing some erasure in Flow and all of it is related to patterns. I think that we should consider moving all these erasure to either TransTypes or TransPatterns

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

PR Review Comment: https://git.openjdk.org/jdk/pull/21606#discussion_r1809544754