Add unit test for behavior of lexer with input-position-sensitive predicates

tool/test/org/antlr/v4/test/TestLexerExec.java

@@ -266,6 +266,31 @@ public class TestLexerExec extends BaseTest {
 		assertEquals(expecting, found);
 	}
 
+	@Test public void testLexerInputPositionSensitivePredicates() throws Exception {
+		// The predicates here make sense on the left edge, but are currently
+		// only working on the right edge... resolving this would remove the
+		// need for Lexer.getSpeculativeText as well.
+		String grammar =
+			"lexer grammar L;\n"+
+			"WORD1 : ID1+ {System.out.println(getText());} ;\n"+
+			"WORD2 : ID2+ {System.out.println(getText());} ;\n"+
+			"fragment ID1 : {getCharPositionInLine()<2}? [a-zA-Z];\n"+
+			"fragment ID2 : {getCharPositionInLine()>=2}? [a-zA-Z];\n"+
+			"WS : (' '|'\\n') -> skip;\n";
+		String found = execLexer("L.g4", grammar, "L", "a cde\nabcde\n");
+		String expecting =
+			"a\n" +
+			"cde\n" +
+			"ab\n" +
+			"cde\n" +
+			"[@0,0:0='a',<1>,1:0]\n" +
+			"[@1,2:4='cde',<2>,1:2]\n" +
+			"[@2,6:7='ab',<1>,2:0]\n" +
+			"[@3,8:10='cde',<2>,2:2]\n" +
+			"[@4,12:11='<EOF>',<-1>,3:0]\n";
+		assertEquals(expecting, found);
+	}
+
 	@Test public void testActionExecutedInDFA() throws Exception {
 		String grammar =
 			"lexer grammar L;\n"+