From f528318a82e99793a0afab1f2f792524c3f1f48c Mon Sep 17 00:00:00 2001
From: Anders Hejlsberg <andersh@microsoft.com>
Date: Mon, 25 Oct 2021 07:36:17 -0700
Subject: [PATCH] Call isDeeplyNestedType only when something changed

---
 src/compiler/checker.ts | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 3168327c88..9f2ee97277 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -18714,13 +18714,13 @@ namespace ts {
                 if (recursionFlags & RecursionFlags.Source) {
                     (sourceStack || (sourceStack = []))[sourceDepth] = source;
                     sourceDepth++;
+                    if (!(expandingFlags & ExpandingFlags.Source) && isDeeplyNestedType(source, sourceStack, sourceDepth)) expandingFlags |= ExpandingFlags.Source;
                 }
                 if (recursionFlags & RecursionFlags.Target) {
                     (targetStack || (targetStack = []))[targetDepth] = target;
                     targetDepth++;
+                    if (!(expandingFlags & ExpandingFlags.Target) && isDeeplyNestedType(target, targetStack, targetDepth)) expandingFlags |= ExpandingFlags.Target;
                 }
-                if (!(expandingFlags & ExpandingFlags.Source) && isDeeplyNestedType(source, sourceStack, sourceDepth)) expandingFlags |= ExpandingFlags.Source;
-                if (!(expandingFlags & ExpandingFlags.Target) && isDeeplyNestedType(target, targetStack, targetDepth)) expandingFlags |= ExpandingFlags.Target;
                 if (expandingFlags !== ExpandingFlags.Both) {
                     tracing?.push(tracing.Phase.CheckTypes, "structuredTypeRelatedTo", { sourceId: source.id, targetId: target.id });
                     result = structuredTypeRelatedTo(source, target, reportErrors, intersectionState);