fixed problem with unordered groups and non-trivial cardinalities in

nested prefix alternatives analysis

now flattenPaths() considers following repetitions

new problem: unordered groups and non-trivial cardinalities without
non-optional elements causes explosion of generated alternatives, which
in turn cause the identity analysis to go out of control
example: S: ('a'? | 'b'?)+
with a token limit of 10 the nested prefix alternatives analysis would
generate over 1300 alternatives

current quick fix: limit of alternatives

org.eclipse.xtext.tests/src/org/eclipse/xtext/xtext/generator/hoisting/HoistingProcessorTest.java

@@ -14,6 +14,7 @@ import org.eclipse.xtext.AbstractRule;
 import org.eclipse.xtext.Alternatives;
 import org.eclipse.xtext.Grammar;
 import org.eclipse.xtext.Group;
+import org.eclipse.xtext.Keyword;
 import org.eclipse.xtext.UnorderedGroup;
 import org.eclipse.xtext.XtextStandaloneSetup;
 import org.eclipse.xtext.resource.XtextResource;
@@ -434,7 +435,7 @@ public class HoistingProcessorTest extends AbstractXtextTests {
 		assertEquals("((" + getSyntaxForKeywordToken("a", 1) + " || (p0)) && (" + getSyntaxForKeywordToken("b", 1) + " || (p1)))", guard.render());
 	}
 	
-	@Test(expected = TokenAnalysisAbortedException.class)
+	@Test
 	public void testUnorderedGroupWithEmptyPathsWithoutContext_expectTokenAnalysisAbortedException() throws Exception {		
 		// @formatter:off
 		String model =
@@ -936,6 +937,44 @@ public class HoistingProcessorTest extends AbstractXtextTests {
 		);
 	}
 	
+	@Test
+	public void testNestedAlternativesWithIdenticalPrefix_parentElementShouldNotBeChanged_expectContextCheckInResult() throws Exception {
+		// @formatter:off
+		String model =
+			MODEL_PREAMBLE +
+			"S: {S} $$ p0 $$?=> ('a')? \n" +
+			" | {S} $$ p1 $$?=> ('b')? ;\n";
+		// @formatter:off
+		XtextResource resource = getResourceFromString(model);
+		Grammar grammar = ((Grammar) resource.getContents().get(0));
+		hoistingProcessor.init(grammar);
+		AbstractRule rule = getRule(grammar, "S");
+		
+		HoistingGuard guard = hoistingProcessor.findHoistingGuard(rule.getAlternatives());
+		assertFalse(guard.isTrivial());
+		assertTrue(guard.hasTerminal());
+		assertEquals(
+				"(" + 
+					"(" + getSyntaxForEofToken(1) + " || (p0) || (p1)) && " + 
+					"(" + getSyntaxForKeywordToken("a", 1) + " || (p0)) && " + 
+					"(" + getSyntaxForKeywordToken("b", 1) + " || (p1))" +
+				")", 
+			guard.render()
+		);
+		
+		// check sizes of groups and cardinalities of keywords
+		Alternatives alternatives = (Alternatives) rule.getAlternatives();
+		assertEquals(2, alternatives.getElements().size());
+		Group group = (Group) alternatives.getElements().get(0);
+		assertEquals(3, group.getElements().size());
+		Keyword keyword = (Keyword) group.getElements().get(2);
+		assertEquals("?", keyword.getCardinality());
+		group = (Group) alternatives.getElements().get(1);
+		assertEquals(3, group.getElements().size());
+		keyword = (Keyword) group.getElements().get(2);
+		assertEquals("?", keyword.getCardinality());
+	}
+	
 	// symbolic analysis not yet implemented
 	//@Test
 	public void testAlternativesIdenticalPathsWithSymbolicAnalysis() throws Exception {

org.eclipse.xtext.xtext.generator/src/org/eclipse/xtext/xtext/generator/parser/antlr/hoisting/HoistingProcessor.java

@@ -16,11 +16,14 @@ import java.util.LinkedList;
 import java.util.Map;
 import java.util.List;
 import java.util.stream.Collectors;
+import java.util.stream.Stream;
 
 import org.apache.log4j.Logger;
 
 import static org.eclipse.emf.ecore.util.EcoreUtil.*;
 
+import org.eclipse.emf.ecore.EObject;
+import org.eclipse.emf.ecore.util.EcoreUtil;
 import org.eclipse.xtext.AbstractElement;
 import org.eclipse.xtext.AbstractRule;
 import org.eclipse.xtext.AbstractSemanticPredicate;
@@ -28,6 +31,7 @@ import org.eclipse.xtext.Action;
 import org.eclipse.xtext.Alternatives;
 import org.eclipse.xtext.Assignment;
 import org.eclipse.xtext.CompoundElement;
+import org.eclipse.xtext.EcoreUtil2;
 import org.eclipse.xtext.Grammar;
 import org.eclipse.xtext.Group;
 import org.eclipse.xtext.JavaAction;
@@ -41,7 +45,6 @@ import static org.eclipse.xtext.GrammarUtil.*;
 
 import org.eclipse.xtext.xtext.generator.parser.antlr.JavaCodeUtils;
 import org.eclipse.xtext.xtext.generator.parser.antlr.hoisting.exceptions.NestedPrefixAlternativesException;
-import org.eclipse.xtext.xtext.generator.parser.antlr.hoisting.exceptions.OptionalCardinalityWithoutContextException;
 import org.eclipse.xtext.xtext.generator.parser.antlr.hoisting.exceptions.TokenAnalysisAbortedException;
 import org.eclipse.xtext.xtext.generator.parser.antlr.hoisting.exceptions.UnsupportedConstructException;
 import org.eclipse.xtext.xtext.generator.parser.antlr.hoisting.guards.AlternativeTokenSequenceGuard;
@@ -125,13 +128,53 @@ public class HoistingProcessor {
 		return virtualNopJavaAction;
 	}
 	
-	private CompoundElement flattenPaths(CompoundElement original, List<AbstractElement> paths, List<? extends HoistingGuard> guards) {
+	private CompoundElement flattenPaths(AbstractElement original, List<AbstractElement> paths, List<? extends HoistingGuard> guards) {
-		// work on copy of original to preserve eParent
+		// we need to preserve parent for context analysis
-		CompoundElement flattened = copy(original);
+		// but we are not allowed to change the tree
+		// -> clone parent
+		EObject clonedParent = copy(original.eContainer());
+		CompoundElement flattened = XtextFactory.eINSTANCE.createAlternatives();
+		
+		if (clonedParent instanceof CompoundElement) {
+			setElementsOfCompoundElement((CompoundElement) clonedParent, 
+					((CompoundElement) clonedParent).getElements().stream()
+						.map(e -> {
+							if (e == original) {
+								return flattened;
+							} else {
+								return e;
+							}
+						}));
+		} else {
+			EcoreUtil2.setEParent(flattened, clonedParent);
+		}
+		
+		Stream<AbstractElement> pathsStream = paths.stream();
+		
+		if (original instanceof UnorderedGroup) {
+			// in case original element is UnorderedGroup add original after each path
+			// so token analysis can fetches all possible paths correctly
+			
+			pathsStream = pathsStream
+				.map(p -> {
+					Group virtualGroup = XtextFactory.eINSTANCE.createGroup();
+					setElementsOfCompoundElement(virtualGroup, Arrays.asList(p, copy(original)));
+					return virtualGroup;
+				});
+		}
+		
 		setElementsOfCompoundElement(flattened,
 			StreamUtils.zip(
-				paths.stream()
+				pathsStream
-					.map(analysis::getAllPossiblePaths),
+					.map(analysis::getAllPossiblePaths)
+					.map(l1 -> l1.stream()
+						.map(l2 -> l2.stream()
+							.map(EcoreUtil::copy)
+							// remove cardinality; token analysis already handled that
+							.peek(e -> e.setCardinality(null))
+							.collect(Collectors.toList())
+						).collect(Collectors.toList())
+					),
 				guards.stream()
 					.map(HoistingGuard.class::cast),
 				(List<List<AbstractElement>> e, HoistingGuard g) -> Tuples.pair(e, g)
@@ -179,6 +222,8 @@ public class HoistingProcessor {
 		return flattened;
 	}
 	
+	boolean hasSeen = false;
+	
 	private HoistingGuard findGuardForAlternatives(CompoundElement alternatives, AbstractRule currentRule) {
 		log.info("find guard for alternative");
 		
@@ -249,12 +294,20 @@ public class HoistingProcessor {
 				// -> flatten paths to alternative and try again
 				// this is very inefficient
 				log.warn("nested prefix alternatives detected");
-				log.warn("avoid these since they can't be handled efficiency");
+				log.warn("avoid these since they can't be handled efficiently");
 				log.info(abstractElementToString(alternatives));
 				
 				CompoundElement flattened = flattenPaths(alternatives, paths, guards);
 				log.info(abstractElementToString(flattened));
 				
+				log.info(flattened.getElements().size());
+				// TODO: value configurable?
+				if (flattened.getElements().size() > 100) {
+					throw new NestedPrefixAlternativesException("nested prefix alternatives cant be analysed because of too many paths");
+				}
+				
+				//throw new RuntimeException();
+				
 				return findGuardForAlternatives(flattened, currentRule);
 			} catch(TokenAnalysisAbortedException e) {
 				throw new TokenAnalysisAbortedException(e.getMessage(), e, currentRule);
@@ -285,9 +338,7 @@ public class HoistingProcessor {
 			AbstractElement element = iterator.next();
 			
 			String cardinality = element.getCardinality();
-			if (cardinality == null ||
+			if (isTrivialCardinality(element) || isOneOrMoreCardinality(element)) {
-			    cardinality.equals("") ||
-			    cardinality.equals("+")) {
 				
 				HoistingGuard guard = findGuardForElementWithTrivialCardinality(element, currentRule);
 				groupGuard.add(guard);
@@ -300,18 +351,12 @@ public class HoistingProcessor {
 					groupGuard.setHasTerminal();
 					break;
 				}
-			} else if (cardinality.equals("?") ||
+			} else if (isOptionalCardinality(element)) {
-			           cardinality.equals("*")) {
 				// though not technically necessary, rewrite tree to context checks are not needed 
 				
 				// rewrite cardinality to alternatives
 				// A? B -> A B | B
-				// A* B -> A+ B | B -> A B (see above)
+				// A* B -> A+ B | B -> A B | B (see above)
-				
-				// we need a clone of the element because we need to set the cardinality without changing the
-				// original syntax tree
-				AbstractElement clonedElement = copy(element);
-				clonedElement.setCardinality(null);
 				
 				// make copy of every element because we can't use any element twice
 				List<AbstractElement> remainingElementsInGroup = StreamUtils.fromIterator(iterator)
@@ -319,33 +364,50 @@ public class HoistingProcessor {
 				
 				if (remainingElementsInGroup.isEmpty()) {
 					// B is empty
-					// context is needed to generate virtual alternatives
+					// context will be taken from parent element
-					throw new OptionalCardinalityWithoutContextException("no context in group", currentRule);
+					
+					HoistingGuard guard = findGuardForOptionalCardinalityWithoutContext(element, currentRule);
+					groupGuard.add(guard);
+					
+					if (guard.hasTerminal()) {
+						groupGuard.setHasTerminal();
+					}
+					
+					// there are no following elements
+					break;
+				} else {
+					// B is non-empty
+					// -> construct context for alternatives
+					
+					// we need a clone of the element because we need to set the cardinality without changing the
+					// original syntax tree
+					AbstractElement clonedElement = copy(element);
+					clonedElement.setCardinality(null);
+					
+					// make copy of first branch and add the cloned element
+					List<AbstractElement> remainingElementsInGroupIncludingCurrent = new LinkedList<>(remainingElementsInGroup);
+					remainingElementsInGroupIncludingCurrent.add(0, clonedElement);
+							
+					Group virtualPathRemaining = XtextFactory.eINSTANCE.createGroup();
+					setElementsOfCompoundElement(virtualPathRemaining, remainingElementsInGroup);
+					
+					Group virtualPathRemainingPlusCurrent = XtextFactory.eINSTANCE.createGroup();
+					setElementsOfCompoundElement(virtualPathRemainingPlusCurrent, remainingElementsInGroupIncludingCurrent);
+					
+					Alternatives virtualAlternatives = XtextFactory.eINSTANCE.createAlternatives();
+					setElementsOfCompoundElement(virtualAlternatives, Arrays.asList(virtualPathRemaining, virtualPathRemainingPlusCurrent));
+					
+					// get Guard for virtual alternatives
+					HoistingGuard guard = findGuardForElementWithTrivialCardinality(virtualAlternatives, currentRule);
+					groupGuard.add(guard);
+					
+					if (guard.hasTerminal()) {
+						groupGuard.setHasTerminal();
+					}
+
+					// following elements are included in alternative, no need to check further
+					break;
 				}
-				
-				// make copy of first branch and add the cloned element
-				List<AbstractElement> remainingElementsInGroupIncludingCurrent = new LinkedList<>(remainingElementsInGroup);
-				remainingElementsInGroupIncludingCurrent.add(0, clonedElement);
-						
-				Group virtualPathRemaining = XtextFactory.eINSTANCE.createGroup();
-				setElementsOfCompoundElement(virtualPathRemaining, remainingElementsInGroup);
-				
-				Group virtualPathRemainingPlusCurrent = XtextFactory.eINSTANCE.createGroup();
-				setElementsOfCompoundElement(virtualPathRemainingPlusCurrent, remainingElementsInGroupIncludingCurrent);
-				
-				Alternatives virtualAlternatives = XtextFactory.eINSTANCE.createAlternatives();
-				setElementsOfCompoundElement(virtualAlternatives, Arrays.asList(virtualPathRemaining, virtualPathRemainingPlusCurrent));
-				
-				// get Guard for virtual alternatives
-				HoistingGuard guard = findGuardForElementWithTrivialCardinality(virtualAlternatives, currentRule);
-				groupGuard.add(guard);
-				
-				if (guard.hasTerminal()) {
-					groupGuard.setHasTerminal();
-				}
-				
-				// following elements are included in alternative, no need to check further
-				break;
 			} else {
 				throw new IllegalArgumentException("unknown cardinality: " + cardinality);
 			}

org.eclipse.xtext.xtext.generator/src/org/eclipse/xtext/xtext/generator/parser/antlr/hoisting/pathAnalysis/TokenAnalysis.java

@@ -141,7 +141,7 @@ public class TokenAnalysis {
 	}
 	
 	
-	private TokenAnalysisPaths getTokenPathsContext(AbstractElement last, TokenAnalysisPaths prefix) {
+	private TokenAnalysisPaths getTokenPathsContext(AbstractElement last, TokenAnalysisPaths prefix, boolean shortcutEndlessLoops) {
 		log.info("get context for: " + abstractElementToShortString(last));
 		
 		List<AbstractElement> context = getNextElementsInContext(last);
@@ -160,13 +160,13 @@ public class TokenAnalysis {
 		
 		for (AbstractElement element : context) {			
 			TokenAnalysisPaths path = new TokenAnalysisPaths(prefix);
-			path = getTokenPaths(element, path, false, false);
+			path = getTokenPaths(element, path, false, false, shortcutEndlessLoops);
 			if (!path.isDone() && element != null) {
 				if (path.getMinPosition() == currentPosition) {
 					throw new TokenAnalysisAbortedException("no progress in context analysis");
 				}
 				
-				path = getTokenPathsContext(element, path);
+				path = getTokenPathsContext(element, path, shortcutEndlessLoops);
 			}
 			if (path.isDone()) {
 				result = result.merge(path);
@@ -179,11 +179,11 @@ public class TokenAnalysis {
 		return result;
 	}
 	
-	private TokenAnalysisPaths getTokenPathsTrivial(Group path, TokenAnalysisPaths prefix) {
+	private TokenAnalysisPaths getTokenPathsTrivial(Group path, TokenAnalysisPaths prefix, boolean shortcutEndlessLoops) {
 		TokenAnalysisPaths result = new TokenAnalysisPaths(prefix);
 		
 		for(AbstractElement element : path.getElements()) {
-			result = getTokenPaths(element, result, false, false);
+			result = getTokenPaths(element, result, false, false, shortcutEndlessLoops);
 			if (result.isDone()) {
 				break;
 			}
@@ -191,16 +191,18 @@ public class TokenAnalysis {
 		
 		return result;
 	}
-	private TokenAnalysisPaths getTokenPathsTrivial(Alternatives path, TokenAnalysisPaths prefix) {
+	private TokenAnalysisPaths getTokenPathsTrivial(Alternatives path, TokenAnalysisPaths prefix, boolean shortcutEndlessLoops) {
 		TokenAnalysisPaths result = TokenAnalysisPaths.empty(prefix);
 		
 		for(AbstractElement element : path.getElements()) {
-			result = result.merge(getTokenPaths(element, prefix, false, false));
+			result = result.merge(getTokenPaths(element, prefix, false, false, shortcutEndlessLoops));
 		}
 		
 		return result;
 	}
-	private TokenAnalysisPaths getTokenPathsTrivial(UnorderedGroup path, TokenAnalysisPaths prefix) {
+	private TokenAnalysisPaths getTokenPathsTrivial(UnorderedGroup path, TokenAnalysisPaths prefix, boolean shortcutEndlessLoops) {
+		log.info("unordered group");
+		
 		TokenAnalysisPaths result;
 		TokenAnalysisPaths current;
 		
@@ -213,45 +215,65 @@ public class TokenAnalysis {
 		int currentPosition = result.getMinPosition();
 		
 		do {
+			log.info("unordered group loop");
+			
 			current = TokenAnalysisPaths.empty(result);
+			current.resetProgress();
 			for (AbstractElement element : path.getElements()) {
-				current = current.merge(getTokenPaths(element, result, false, false));
+				log.info(abstractElementToShortString(element));
+				log.info(current.hasProgress() + " - " + current.getSize());
+				current = current.merge(getTokenPaths(element, result, false, false, shortcutEndlessLoops));
+				log.info(current.hasProgress() + " - " + current.getSize());
 			}
 			
+			result.resetProgress();
+			result = result.merge(current);
+			
 			if (current.getMinPosition() == currentPosition) {
-				throw new TokenAnalysisAbortedException("no progress in loop");
+				// endless loop
+				// result will never be done since there is no progress to the shortest path
+				if (shortcutEndlessLoops) {
+					if (!result.hasProgress()) {
+						// no progress
+						// abort endless loop
+						break;
+					} else {
+						// there is still some progress done
+						continue;
+					}
+				} else {
+					throw new TokenAnalysisAbortedException("no progress in loop");
+				}
 			}
-			
-			result = result.merge(current);
 		} while(!current.isDone());
 		
 		return result;
 	}
 	
-	private TokenAnalysisPaths getTokenPathsTrivial(AbstractElement path, TokenAnalysisPaths prefix) {
+	private TokenAnalysisPaths getTokenPathsTrivial(AbstractElement path, TokenAnalysisPaths prefix, boolean shortcutEndlessLoops) {
 		return new XtextSwitch<TokenAnalysisPaths>() {
 			@Override
 			public TokenAnalysisPaths caseGroup(Group group) {
-				return getTokenPathsTrivial(group, prefix);
+				return getTokenPathsTrivial(group, prefix, shortcutEndlessLoops);
 			};
 			@Override
 			public TokenAnalysisPaths caseAlternatives(Alternatives alternatives) {
-				return getTokenPathsTrivial(alternatives, prefix);
+				return getTokenPathsTrivial(alternatives, prefix, shortcutEndlessLoops);
 			};
 			@Override
 			public TokenAnalysisPaths caseUnorderedGroup(UnorderedGroup unorderedGroup) {
-				return getTokenPathsTrivial(unorderedGroup, prefix);
+				return getTokenPathsTrivial(unorderedGroup, prefix, shortcutEndlessLoops);
 			};
 			@Override
 			public TokenAnalysisPaths caseAssignment(Assignment assignment) {
-				return getTokenPaths(assignment.getTerminal(), prefix, false, false);
+				return getTokenPaths(assignment.getTerminal(), prefix, false, false, shortcutEndlessLoops);
 			};
 			@Override
 			public TokenAnalysisPaths caseRuleCall(RuleCall call) {
 				if (isParserRuleCall(call) || 
 				    isEnumRuleCall(call)
 				) {
-					return getTokenPaths(call.getRule().getAlternatives(), prefix, false, false);
+					return getTokenPaths(call.getRule().getAlternatives(), prefix, false, false, shortcutEndlessLoops);
 				} else {
 					// go to default case
 					return null;
@@ -274,7 +296,9 @@ public class TokenAnalysis {
 	}
 	
 	// analyseContext implies needsLength
-	private TokenAnalysisPaths getTokenPaths(AbstractElement path, TokenAnalysisPaths prefix, boolean analyseContext, boolean needsLength) {
+	private TokenAnalysisPaths getTokenPaths(
+			AbstractElement path, TokenAnalysisPaths prefix, boolean analyseContext, boolean needsLength, boolean shortcutEndlessLoops
+	) {
 		if (prefix.isDone()) {
 			return prefix;
 		}
@@ -290,7 +314,7 @@ public class TokenAnalysis {
 		
 		if (isOptionalCardinality(path)) {
 			if (analyseContext) {
-				result = getTokenPathsContext(path, prefix);
+				result = getTokenPathsContext(path, prefix, shortcutEndlessLoops);
 			} else if (needsLength) {
 				throw new TokenAnalysisAbortedException("token expected but path is optional");
 			} else {
@@ -302,16 +326,17 @@ public class TokenAnalysis {
 		
 		boolean loop = isMultipleCardinality(path);
 		
-		int currentPosition = result.getMinPosition();
+		int currentMinPosition = result.getMinPosition();
 		
-		do {	
+		do {
-			TokenAnalysisPaths tokenPaths = getTokenPathsTrivial(path, result);
+			result.resetProgress();
+			TokenAnalysisPaths tokenPaths = getTokenPathsTrivial(path, result, shortcutEndlessLoops);
 			
 			if (tokenPaths.isDone()) {
 				result = result.merge(tokenPaths);
 				break;
 			} else if (analyseContext) {
-				tokenPaths = getTokenPathsContext(path, tokenPaths);
+				tokenPaths = getTokenPathsContext(path, tokenPaths, shortcutEndlessLoops);
 				result = result.merge(tokenPaths);
 			} else if (needsLength) {
 				throw new TokenAnalysisAbortedException("requested length not satisfyable");
@@ -320,10 +345,23 @@ public class TokenAnalysis {
 			}
 			
 			if (loop) {
-				if (result.getMinPosition() == currentPosition) {
+				if (result.getMinPosition() == currentMinPosition) {
-					throw new TokenAnalysisAbortedException("no progress in loop");
+					// endless loop
+					// result will never be done since there is no progress to the shortest path
+					if (shortcutEndlessLoops) {
+						if (!result.hasProgress()) {
+							// no progress
+							// abort endless loop
+							break;
+						} else {
+							// there is still some progress done
+							continue;
+						}
+					} else {
+						throw new TokenAnalysisAbortedException("no progress in loop");
+					}
 				} else {
-					currentPosition = result.getMinPosition();
+					currentMinPosition = result.getMinPosition();
 				}
 			}
 		} while (loop);
@@ -332,11 +370,11 @@ public class TokenAnalysis {
 	}
 	
 	private List<List<Token>> getTokenPaths(AbstractElement path, List<Integer> indexes, boolean analyseContext) throws TokenAnalysisAbortedException {
-		return getTokenPaths(path, new TokenAnalysisPaths(indexes), analyseContext, true).getTokenPaths();
+		return getTokenPaths(path, new TokenAnalysisPaths(indexes), analyseContext, true, false).getTokenPaths();
 	}
 	
 	private List<List<Token>> getTokenPathsContextOnly(AbstractElement path, List<Integer> indexes) {
-		return getTokenPathsContext(path, new TokenAnalysisPaths(indexes)).getTokenPaths();
+		return getTokenPathsContext(path, new TokenAnalysisPaths(indexes), false).getTokenPaths();
 	}
 	
 	private boolean arePathsIdenticalSymbolic(AbstractElement path1, AbstractElement path2) throws SymbolicAnalysisFailedException {
@@ -364,8 +402,8 @@ public class TokenAnalysis {
 			List<Integer> range = range(0,  i);
 			
 			// there shouldn't be a TokenAnalysisAbortedException if needsLength is false
-			tokenPaths1 = getTokenPaths(path1, new TokenAnalysisPaths(range), false, false);
+			tokenPaths1 = getTokenPaths(path1, new TokenAnalysisPaths(range), false, false, false);
-			tokenPaths2 = getTokenPaths(path2, new TokenAnalysisPaths(range), false, false);
+			tokenPaths2 = getTokenPaths(path2, new TokenAnalysisPaths(range), false, false, false);
 			
 			Set<Set<Token>> tokenListSet1 = tokenPaths1.getTokenPaths().stream().map(HashSet::new).collect(Collectors.toSet());
 			Set<Set<Token>> tokenListSet2 = tokenPaths2.getTokenPaths().stream().map(HashSet::new).collect(Collectors.toSet());
@@ -530,7 +568,7 @@ public class TokenAnalysis {
 	}
 	
 	public List<List<AbstractElement>> getAllPossiblePaths(AbstractElement path) {
-		return getTokenPaths(path, new TokenAnalysisPaths(range(0, config.getTokenLimit() + 1)), false, false)
+		return getTokenPaths(path, new TokenAnalysisPaths(range(0, config.getTokenLimit() + 1)), false, false, true)
 				.getTokenPaths()
 				.stream()
 				.map(l -> l.stream()

org.eclipse.xtext.xtext.generator/src/org/eclipse/xtext/xtext/generator/parser/antlr/hoisting/pathAnalysis/TokenAnalysisPath.java

@@ -49,15 +49,19 @@ public class TokenAnalysisPath {
 		}
 	}
 	
-	public void add(AbstractElement element) {
+	public boolean add(AbstractElement element) {
 		if (isDone())
-			return;
+			return false;
 		
 		if (remainingIndexes.get(0) <= 0) {
 			path.add(Token.fromElement(element, position));
 			remainingIndexes.remove(0);
+			shift();
+			return true;
+		} else {
+			shift();
+			return false;
 		}
-		shift();
 	}
 	
 	public List<Token> getTokenPath() {
@@ -70,4 +74,33 @@ public class TokenAnalysisPath {
 				path.stream().map(Token::toString).collect(Collectors.joining(", ")) + "),\n    (" +
 				remainingIndexes.stream().map(Object::toString).collect(Collectors.joining(", ")) + ")\n  )";
 	}
+
+	@Override
+	public int hashCode() {
+		final int prime = 31;
+		int result = 1;
+		result = prime * result + ((path == null) ? 0 : path.hashCode());
+		result = prime * result + position;
+		return result;
+	}
+
+	@Override
+	public boolean equals(Object obj) {
+		if (this == obj)
+			return true;
+		if (obj == null)
+			return false;
+		if (getClass() != obj.getClass())
+			return false;
+		TokenAnalysisPath other = (TokenAnalysisPath) obj;
+		if (path == null) {
+			if (other.path != null)
+				return false;
+		} else if (!path.equals(other.path))
+			return false;
+		if (position != other.position)
+			return false;
+		return true;
+	}
+	
 }

org.eclipse.xtext.xtext.generator/src/org/eclipse/xtext/xtext/generator/parser/antlr/hoisting/pathAnalysis/TokenAnalysisPaths.java

@@ -8,19 +8,21 @@
  *******************************************************************************/
 package org.eclipse.xtext.xtext.generator.parser.antlr.hoisting.pathAnalysis;
 
-import java.util.LinkedList;
+import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.stream.Collectors;
 
 import org.eclipse.xtext.AbstractElement;
 import org.eclipse.xtext.xtext.generator.parser.antlr.hoisting.token.Token;
+import org.eclipse.xtext.xtext.generator.parser.antlr.hoisting.utils.StreamUtils;
 
 /**
- * @author overflow - Initial contribution and API
+ * @author overflow - Initial contribution and APILinkedHashSet
  */
 public class TokenAnalysisPaths {
-	private List<TokenAnalysisPath> tokenPaths = new LinkedList<>();
+	private LinkedHashSet<TokenAnalysisPath> tokenPaths = new LinkedHashSet<>();
 	private boolean isEmpty = false;
+	private boolean hasProgress = false;
 	
 	public List<List<Token>> getTokenPaths() {
 		return tokenPaths.stream()
@@ -36,23 +38,34 @@ public class TokenAnalysisPaths {
 	public TokenAnalysisPaths(TokenAnalysisPaths prefix) {
 		this.tokenPaths = prefix.tokenPaths.stream()
 				.map(TokenAnalysisPath::new)
-				.collect(Collectors.toList());
+				.collect(StreamUtils.collectToLinkedHashSet());
+		this.hasProgress = prefix.hasProgress;
 	}
 	
 	public boolean isDone() {
 		return !isEmpty && tokenPaths.stream().allMatch(TokenAnalysisPath::isDone);
 	}
 	
+	public boolean hasProgress() {
+		return hasProgress;
+	}
+	
+	public void resetProgress() {
+		hasProgress = false;
+	}
+	
 	public void add(AbstractElement element) {
-		tokenPaths.forEach(p -> p.add(element));
+		tokenPaths.forEach(p -> hasProgress = p.add(element) || hasProgress);
 	}
 	
 	public TokenAnalysisPaths merge(TokenAnalysisPaths other) {
 		if (isEmpty) {
 			return other;
 		} else {
-			// TODO: implement hashCode and equals to check for duplicates right awaz
+			// set hasProgress if other has progress and progress is merged
-			this.tokenPaths.addAll(other.tokenPaths);
+			if (this.tokenPaths.addAll(other.tokenPaths)) {
+				this.hasProgress |= other.hasProgress;
+			}
 			return this;
 		}
 	}
@@ -71,6 +84,10 @@ public class TokenAnalysisPaths {
 		return tokenPaths.stream().map(TokenAnalysisPath::getPosition).mapToInt(Integer::intValue).max().getAsInt();
 	}
 	
+	public int getSize() {
+		return tokenPaths.size();
+	}
+	
 	@Override
 	public String toString() {
 		if (isEmpty) {

org.eclipse.xtext.xtext.generator/src/org/eclipse/xtext/xtext/generator/parser/antlr/hoisting/utils/DebugUtils.java

@@ -26,6 +26,7 @@ import org.eclipse.xtext.JavaAction;
 import org.eclipse.xtext.Keyword;
 import org.eclipse.xtext.ParserRule;
 import org.eclipse.xtext.RuleCall;
+import org.eclipse.xtext.UnorderedGroup;
 import org.eclipse.xtext.util.XtextSwitch;
 
 import com.google.common.base.Strings;
@@ -66,6 +67,16 @@ public class DebugUtils {
 				return true;
 			};
 			@Override
+			public Boolean caseUnorderedGroup(UnorderedGroup object) {
+				builder.append("Unordered Group (\n");
+				object.getElements().forEach(e -> {
+					abstractElementToString(e, builder, indentation + 1, calledRules);
+				});
+				builder.append(indentationString);
+				builder.append(")");
+				return true;
+			};
+			@Override
 			public Boolean caseRuleCall(RuleCall object) {
 				AbstractRule rule = object.getRule();
 				if (rule instanceof ParserRule) {
@@ -139,6 +150,13 @@ public class DebugUtils {
 				return true;
 			};
 			@Override
+			public Boolean caseUnorderedGroup(UnorderedGroup object) {
+				builder.append("UnorderedGroup (");
+				builder.append(object.getElements().size());
+				builder.append(")");
+				return true;
+			};
+			@Override
 			public Boolean caseRuleCall(RuleCall object) {
 				AbstractRule rule = object.getRule();
 				if (rule instanceof ParserRule) {

org.eclipse.xtext.xtext.generator/src/org/eclipse/xtext/xtext/generator/parser/antlr/hoisting/utils/StreamUtils.java

@@ -9,14 +9,15 @@
 package org.eclipse.xtext.xtext.generator.parser.antlr.hoisting.utils;
 
 import java.util.Iterator;
+import java.util.LinkedHashSet;
 import java.util.Spliterator;
 import java.util.Spliterators;
 import java.util.function.BiFunction;
+import java.util.function.Supplier;
+import java.util.stream.Collector;
 import java.util.stream.Stream;
 import java.util.stream.StreamSupport;
 
-import com.google.common.base.Splitter;
-
 /**
  * @author overflow - Initial contribution and API
  */
@@ -43,4 +44,14 @@ public class StreamUtils {
 	public static <A> Stream<A> fromIterator(Iterator<A> iterator) {
 		return StreamSupport.stream(Spliterators.spliteratorUnknownSize(iterator, Spliterator.NONNULL), false);
 	}
+	
+	public static <T> Collector<T, ?, LinkedHashSet<T>> collectToLinkedHashSet() {
+		return Collector.of(
+			(Supplier<LinkedHashSet<T>>) LinkedHashSet::new, 
+			LinkedHashSet::add, 
+			(a, b) -> {
+				a.addAll(b);
+				return a;
+			}, Collector.Characteristics.IDENTITY_FINISH);
+	}
 }

org.eclipse.xtext/src/org/eclipse/xtext/EcoreUtil2.java

@@ -26,6 +26,7 @@ import java.util.List;
 import java.util.ListIterator;
 import java.util.Map;
 import java.util.Set;
+import java.util.stream.Collectors;
 
 import org.apache.log4j.Logger;
 import org.eclipse.core.runtime.OperationCanceledException;
@@ -835,4 +836,16 @@ public class EcoreUtil2 extends EcoreUtil {
 			return "";
 	}
 
+	public static void setEParent(EObject child, EObject parent) {
+		List<EReference> possibleReferences = parent.eClass().getEAllContainments().stream()
+				.filter(EReference::isContainment)
+				.filter(r -> r.getEReferenceType().isInstance(child))
+				.collect(Collectors.toList());
+		if (possibleReferences.size() != 1) {
+			throw new IllegalArgumentException("no obvious containment reference found");
+		}
+		
+		parent.eSet(possibleReferences.get(0), child);
+	}
+	
 }