Running a cell with an undefined (potentially forward) reference inside a method raised an SPIResolutionException.

void test(Object o) {
    System.out.println(obj); // a typo, meant 'o'
}
test("IJava");

results in

jdk.jshell.spi.SPIResolutionException: resolution exception
	at .test(#44:1)
	at .(#45:1)

Unfortunately this exception is not very informative, nor does it contain much information as presented by JShell.