@Test public void test1MarkWithConsumesInSequence() throws Exception {
		TestingUnbufferedCharStream input = createStream("xyz");
		int m = input.mark();
		input.consume(); // x, moves to y
		input.consume(); // y
		input.consume(); // z, moves to EOF
		assertEquals(IntStream.EOF, input.LA(1));
		assertEquals("xyz\uFFFF", input.getBuffer());
		input.release(m); // wipes buffer
		assertEquals("\uFFFF", input.getBuffer());
	}
It is not valid to pass a mark to {@link IntStream#seek}, but
{@link UnbufferedCharStream} creates marks in such a way that this
invalid usage results in an {@link IllegalArgumentException}.
tool-testsuite/test/org/antlr/v4/test/tool/TestUnbufferedCharStream.java