A DESCRIPTION OF THE PROBLEM :
JLS 14.21 for Java 16 states that

YieldStatement:
   yield Expression ;

but the relevant code parsing this expression does not allow expressions starting with ~ or !:
https://github.com/openjdk/jdk/blob/5cee23a9ed0b7fe2657be7492d9c1f78fcd02ebf/src/jdk.compiler/share/classes/com/sun/tools/javac/parser/JavacParser.java#L2662-L2665

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Compile the attached source code.


EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
The program compiles successfully
ACTUAL -
> javac Yield.java
Yield.java:5: error: not a statement
        yield !1;
        ^
Yield.java:5: error: ';' expected
        yield !1;
             ^
2 errors


---------- BEGIN SOURCE ----------
class Yield {
  public static void main(String... args) {
    int value = switch (1) {
      default -> {
        yield !1;
      }
    };
  }
}

---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
Wrap the expression in ()

FREQUENCY : always