Java 17 Pattern Matching for Switch (JEP-406) compatibility issue

[mcwhitak]

With version 1.12.0 google-java-format does not properly recognize imports utilized only during pattern matched switches.

As an example, for the following hierarchy

package example.model;

public sealed interface SealedInterface {}

public non-sealed interface TypeA {}
public non-sealed interface TypeB {}

and a Java file using this hierarchy with a pattern matched switch

package example;

import example.model.SealedInterface;
import example.model.TypeA;
import example.model.TypeB;

public class Main {
  public void apply(SealedInterface sealedInterface) {
    switch(sealedInterface) {
      case TypeA a -> System.out.println("A!");
      case TypeB b -> System.out.println("B!");
    }
  }
}

google-java-format will flag import example.model.TypeA and import example.model.TypeB as unused and candidates for removal.

I've recreated this bug in a small repo that illustrates the issue.

[lorenzleutgeb]

This appears to be a duplicate of #683 (which turns out to not only apply when throwing exceptions).

[cushon]

This is fixed now: the formatter didn't support pattern matching in switches on Java 17 at all, and there was a separate issue specifically about unused imports. Thanks for the report!