@Test
	public void testConsumeEOF() {
		CharStream input = createStream("");
		assertEquals(IntStream.EOF, input.LA(1));
		assertThrows(IllegalStateException.class, input::consume);
	}
The {@link IntStream} interface does not specify the behavior when the
EOF symbol is consumed, but {@link UnbufferedCharStream} handles this
particular case by throwing an {@link IllegalStateException}.
tool-testsuite/test/org/antlr/v4/test/tool/TestUnbufferedCharStream.java