From 1589e4f57e39aa6c5bb9e0be39f60191cf94f8b9 Mon Sep 17 00:00:00 2001
From: Vladimir Matveev <vladima@microsoft.com>
Date: Thu, 3 Mar 2016 10:47:21 -0800
Subject: [PATCH] set the maximum depth to explore during type inference

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

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 4ca97793073..835fc343f8d 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -6585,6 +6585,7 @@ namespace ts {
         function inferTypes(context: InferenceContext, source: Type, target: Type) {
             let sourceStack: Type[];
             let targetStack: Type[];
+            const maxDepth = 5;
             let depth = 0;
             let inferiority = 0;
             const visited: Map<boolean> = {};
@@ -6713,6 +6714,11 @@ namespace ts {
                         if (isInProcess(source, target)) {
                             return;
                         }
+                        // we delibirately limit the depth we examine to infer types: this speeds up the overall inference process
+                        // and user rarely expects inferences to be made from the deeply nested constituents.
+                        if (depth > maxDepth) {
+                            return;
+                        }
                         if (isDeeplyNestedGeneric(source, sourceStack, depth) && isDeeplyNestedGeneric(target, targetStack, depth)) {
                             return;
                         }