Improve Endless Loop Detection

For BeginEnd and BeginWhile rules, improves the endless loop detection,
detecting multiple rule deep loops and not falsing detecting successively
repeating rules that did not occur at the same place.

Fixes #145.

src/grammar.ts

@@ -961,7 +961,7 @@ function _tokenizeString(grammar: Grammar, lineText: OnigString, isFirstLine: bo
 					stack = stack.setEndRule(pushedRule.getEndWithResolvedBackReferences(lineText.content, captureIndices));
 				}
 
-				if (!hasAdvanced && beforePush.hasSameRuleAs(stack)) {
+				if (stack.hasEndlessLoop(anchorPosition)) {
 					// Grammar pushed the same rule without advancing
 					if (DebugFlags.InDebugMode) {
 						console.error('[2] - Grammar is in an endless loop - Grammar pushed the same rule without advancing');
@@ -988,7 +988,7 @@ function _tokenizeString(grammar: Grammar, lineText: OnigString, isFirstLine: bo
 					stack = stack.setEndRule(pushedRule.getWhileWithResolvedBackReferences(lineText.content, captureIndices));
 				}
 
-				if (!hasAdvanced && beforePush.hasSameRuleAs(stack)) {
+				if (stack.hasEndlessLoop(anchorPosition)) {
 					// Grammar pushed the same rule without advancing
 					if (DebugFlags.InDebugMode) {
 						console.error('[3] - Grammar is in an endless loop - Grammar pushed the same rule without advancing');
@@ -1436,6 +1436,24 @@ export class StackElement implements StackElementDef {
 	public hasSameRuleAs(other: StackElement): boolean {
 		return this.ruleId === other.ruleId;
 	}
+
+	public hasEndlessLoop(anchorPosition: number): boolean {
+		if (anchorPosition === -1) {
+			// method is unavailable
+			return true;
+		}
+
+		let se = this as StackElement;
+
+		while (anchorPosition === se._anchorPos && se.parent !== null) {
+			se = se.parent;
+			if (this.hasSameRuleAs(se)) {
+				// endless loop detected
+				return true;
+			}
+		}
+		return false;
+	}
 }
 
 export class LocalStackElement {