From 40200fcf307fbd53b89f3eafa10384f2ed7ab291 Mon Sep 17 00:00:00 2001
From: Jake Bailey <5341706+jakebailey@users.noreply.github.com>
Date: Mon, 10 Jun 2024 12:00:10 -0700
Subject: [PATCH 1/2] Only use resolutionStart when pushing resolution stack

---
 src/compiler/checker.ts | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 5cefd7aa08717..e63d7d9f8e156 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -10933,7 +10933,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
      * @param propertyName The property name that should be used to query the target for its type
      */
     function pushTypeResolution(target: TypeSystemEntity, propertyName: TypeSystemPropertyName): boolean {
-        const resolutionCycleStartIndex = findResolutionCycleStartIndex(target, propertyName);
+        const resolutionCycleStartIndex = findResolutionCycleStartIndex(target, propertyName, resolutionStart);
         if (resolutionCycleStartIndex >= 0) {
             // A cycle was found
             const { length } = resolutionTargets;
@@ -10948,8 +10948,8 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
         return true;
     }
 
-    function findResolutionCycleStartIndex(target: TypeSystemEntity, propertyName: TypeSystemPropertyName): number {
-        for (let i = resolutionTargets.length - 1; i >= resolutionStart; i--) {
+    function findResolutionCycleStartIndex(target: TypeSystemEntity, propertyName: TypeSystemPropertyName, start = 0): number {
+        for (let i = resolutionTargets.length - 1; i >= start; i--) {
             if (resolutionTargetHasProperty(resolutionTargets[i], resolutionPropertyNames[i])) {
                 return -1;
             }

From 308769772150419331f4baeafec539d310860a9a Mon Sep 17 00:00:00 2001
From: Jake Bailey <5341706+jakebailey@users.noreply.github.com>
Date: Mon, 10 Jun 2024 12:05:58 -0700
Subject: [PATCH 2/2] Refactor into func for clarity

---
 src/compiler/checker.ts | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index e63d7d9f8e156..118119c209bce 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -10948,7 +10948,11 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
         return true;
     }
 
-    function findResolutionCycleStartIndex(target: TypeSystemEntity, propertyName: TypeSystemPropertyName, start = 0): number {
+    function isInResolutionStack(target: TypeSystemEntity, propertyName: TypeSystemPropertyName): boolean {
+        return findResolutionCycleStartIndex(target, propertyName, 0) >= 0;
+    }
+
+    function findResolutionCycleStartIndex(target: TypeSystemEntity, propertyName: TypeSystemPropertyName, start: number): number {
         for (let i = resolutionTargets.length - 1; i >= start; i--) {
             if (resolutionTargetHasProperty(resolutionTargets[i], resolutionPropertyNames[i])) {
                 return -1;
@@ -15907,7 +15911,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
 
     function isResolvingReturnTypeOfSignature(signature: Signature): boolean {
         return signature.compositeSignatures && some(signature.compositeSignatures, isResolvingReturnTypeOfSignature) ||
-            !signature.resolvedReturnType && findResolutionCycleStartIndex(signature, TypeSystemPropertyName.ResolvedReturnType) >= 0;
+            !signature.resolvedReturnType && isInResolutionStack(signature, TypeSystemPropertyName.ResolvedReturnType);
     }
 
     function getRestTypeOfSignature(signature: Signature): Type {
@@ -20184,7 +20188,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
                 if (!type.declaration.nameType) {
                     let constraint;
                     if (
-                        isArrayType(t) || t.flags & TypeFlags.Any && findResolutionCycleStartIndex(typeVariable!, TypeSystemPropertyName.ImmediateBaseConstraint) < 0 &&
+                        isArrayType(t) || t.flags & TypeFlags.Any && !isInResolutionStack(typeVariable!, TypeSystemPropertyName.ImmediateBaseConstraint) &&
                             (constraint = getConstraintOfTypeParameter(typeVariable!)) && everyType(constraint, isArrayOrTupleType)
                     ) {
                         return instantiateMappedArrayType(t, type, prependTypeMapping(typeVariable!, t, mapper));
@@ -31482,7 +31486,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
     }
 
     function isCircularMappedProperty(symbol: Symbol) {
-        return !!(getCheckFlags(symbol) & CheckFlags.Mapped && !(symbol as MappedSymbol).links.type && findResolutionCycleStartIndex(symbol, TypeSystemPropertyName.Type) >= 0);
+        return !!(getCheckFlags(symbol) & CheckFlags.Mapped && !(symbol as MappedSymbol).links.type && isInResolutionStack(symbol, TypeSystemPropertyName.Type));
     }
 
     function getTypeOfPropertyOfContextualType(type: Type, name: __String, nameType?: Type) {