From e7f415d5e517a1020da52dbd8d4d476a730507d0 Mon Sep 17 00:00:00 2001
From: Vladimir Matveev <vladima@microsoft.com>
Date: Mon, 22 Feb 2016 11:50:52 -0800
Subject: [PATCH 1/2] Merge pull request #7163 from Microsoft/cachePairs

do not make inferences with the same source\target pair multiple times
---
 src/compiler/checker.ts | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index e6d3ec5ccea..b4427dbb690 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -6446,6 +6446,7 @@ namespace ts {
             let targetStack: Type[];
             let depth = 0;
             let inferiority = 0;
+            const visited: Map<boolean> = {};
             inferFromTypes(source, target);
 
             function isInProcess(source: Type, target: Type) {
@@ -6575,6 +6576,12 @@ namespace ts {
                             return;
                         }
 
+                        const key = source.id + "," + target.id;
+                        if (hasProperty(visited, key)) {
+                            return;
+                        }
+                        visited[key] = true;
+
                         if (depth === 0) {
                             sourceStack = [];
                             targetStack = [];

From 365e5446da2f4f042e37a55f09187095c3764913 Mon Sep 17 00:00:00 2001
From: Vladimir Matveev <vladima@microsoft.com>
Date: Thu, 3 Mar 2016 12:18:49 -0800
Subject: [PATCH 2/2] Merge pull request #7373 from
 Microsoft/limitInferenceDepth

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 b4427dbb690..44713b2c1db 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -6444,6 +6444,7 @@ 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> = {};
@@ -6572,6 +6573,11 @@ 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;
                         }