RFR: JDK-8214529: Exception while using Anonymous class in switch expression

[Jan Lahoda]

Hi,

In:
https://bugs.openjdk.java.net/browse/JDK-8214529

This is a report that anonymous class' bodies are lost if the anonymous 
class is the break value. This was due to a mistake in desugaring, and 
has been fixed alongside with JDK-8214031, which removes the desugaring. 
But when writing a test for this case, it turned out that "return" 
statements inside the anonymous class are reported as errors:

---
interface TestIntf {
     default int fun() {
         return 1;
     }
}

public class SwitchTest {

         public static void main(String[] args) {
                 int x = 10;
                 var y = switch(x) {
             case 0 -> new TestIntf(){ public int fun() { return 0; }};
             default -> new TestIntf(){};
                         };

                 System.out.println(y.fun());
         }
}
---
---
$ javac --enable-preview --source 12 /tmp/SwitchTest.java
/tmp/SwitchTest.java:12: error: return outside of enclosing switch 
expression
             case 0 -> new TestIntf(){ public int fun() { return 0; }};
                                                          ^
Note: /tmp/SwitchTest.java uses preview language features.
Note: Recompile with -Xlint:preview for details.
1 error
---

This is not appropriate, to my knowledge. The proposed fix is to clear 
the breakResult when creating methodEnv, as is already done for 
lambdaEnv. The breakResult is (also) used to detect inappropriate 
returns nested inside the switch expression, so clearing it eliminates 
the error.

Webrev:
http://cr.openjdk.java.net/~jlahoda/8214529/webrev.00/

How does this look?

Thanks,
     Jan