Whe checking for an endless loop, look through all stack elements entered at the same position

src/grammar.ts

@@ -961,7 +961,7 @@ function _tokenizeString(grammar: Grammar, lineText: OnigString, isFirstLine: bo
 					stack = stack.setEndRule(pushedRule.getEndWithResolvedBackReferences(lineText.content, captureIndices));
 				}
 
-				if (stack.hasEndlessLoop(anchorPosition)) {
+				if (!hasAdvanced && beforePush.hasSameRuleAs(stack)) {
 					// 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 (stack.hasEndlessLoop(anchorPosition)) {
+				if (!hasAdvanced && beforePush.hasSameRuleAs(stack)) {
 					// 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');
@@ -1434,23 +1434,12 @@ 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
+		let el: StackElement | null = this;
+		while (el && el._enterPos === other._enterPos) {
+			if (el.ruleId === other.ruleId) {
 				return true;
 			}
+			el = el.parent;
 		}
 		return false;
 	}