In jshell, if I have a switch statement with a single default label that contains code not reaching the end of the switch statement, jshell will give a syntax error. That used to work in JDK 11.

jshell> var foo = "foo"
foo ==> "foo"

jshell> switch (foo) { default: throw new AssertionError(); }
| Error:
| unreachable statement
| switch (foo) { default: throw new AssertionError(); }
| ^

jshell>