Merge pull request #425 from sharwell/fix-299

Fix 299

tool/src/org/antlr/v4/codegen/model/RuleFunction.java

@@ -307,13 +307,23 @@ public class RuleFunction extends OutputModelObject {
 		 * Common
 		 */
 
+		/**
+		 * Generate a frequency set as the union of two input sets. If an
+		 * element is contained in both sets, the value for the output will be
+		 * the maximum of the two input values.
+		 *
+		 * @param a The first set.
+		 * @param b The second set.
+		 * @return The union of the two sets, with the maximum value chosen
+		 * whenever both sets contain the same key.
+		 */
 		protected static FrequencySet<String> combineMax(FrequencySet<String> a, FrequencySet<String> b) {
 			FrequencySet<String> result = combineAndClip(a, b, 1);
 			for (Map.Entry<String, MutableInt> entry : a.entrySet()) {
 				result.get(entry.getKey()).v = entry.getValue().v;
 			}
 
-			for (Map.Entry<String, MutableInt> entry : a.entrySet()) {
+			for (Map.Entry<String, MutableInt> entry : b.entrySet()) {
 				MutableInt slot = result.get(entry.getKey());
 				slot.v = Math.max(slot.v, entry.getValue().v);
 			}
@@ -321,6 +331,18 @@ public class RuleFunction extends OutputModelObject {
 			return result;
 		}
 
+		/**
+		 * Generate a frequency set as the union of two input sets, with the
+		 * values clipped to a specified maximum value. If an element is
+		 * contained in both sets, the value for the output, prior to clipping,
+		 * will be the sum of the two input values.
+		 *
+		 * @param a The first set.
+		 * @param b The second set.
+		 * @param clip The maximum value to allow for any output.
+		 * @return The sum of the two sets, with the individual elements clipped
+		 * to the maximum value gived by {@code clip}.
+		 */
 		protected static FrequencySet<String> combineAndClip(FrequencySet<String> a, FrequencySet<String> b, int clip) {
 			FrequencySet<String> result = new FrequencySet<String>();
 			for (Map.Entry<String, MutableInt> entry : a.entrySet()) {

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

@@ -377,4 +377,35 @@ public class TestParserExec extends BaseTest {
 		assertEquals("(file (item a) <EOF>)\n", found);
 		assertNull(stderrDuringParse);
 	}
+
+	/**
+	 * This is a regressino test for antlr/antlr4#299 "Repeating subtree not
+	 * accessible in visitor".
+	 * https://github.com/antlr/antlr4/issues/299
+	 */
+	@Test public void testListLabelForClosureContext() throws Exception {
+		String grammar =
+			"grammar T;\n" +
+			"ifStatement\n" +
+			"@after { List<? extends ElseIfStatementContext> items = $ctx.elseIfStatement(); }\n" +
+			"    : 'if' expression\n" +
+			"      ( ( 'then'\n" +
+			"          executableStatement*\n" +
+			"          elseIfStatement*  // <--- problem is here\n" +
+			"          elseStatement?\n" +
+			"          'end' 'if'\n" +
+			"        ) | executableStatement )\n" +
+			"    ;\n" +
+			"\n" +
+			"elseIfStatement\n" +
+			"    : 'else' 'if' expression 'then' executableStatement*\n" +
+			"    ;\n"
+			+ "expression : 'a' ;\n"
+			+ "executableStatement : 'a' ;\n"
+			+ "elseStatement : 'a' ;\n";
+		String input = "a";
+		String found = execParser("T.g4", grammar, "TParser", "TLexer", "expression", input, false);
+		assertEquals("", found);
+		assertNull(stderrDuringParse);
+	}
 }