From b5a5758169c44060277ee2ac181cadad4c7f9dae Mon Sep 17 00:00:00 2001
From: Anders Hejlsberg <andersh@microsoft.com>
Date: Sat, 16 Jul 2016 07:46:28 -0700
Subject: [PATCH] No subtype reduction in createUnionOrIntersectionProperty for
 performance

---
 src/compiler/checker.ts | 14 ++++++++++++--
 src/harness/loggedIO.ts |  2 +-
 2 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 996ad2586df..47fa9918d2b 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -4327,7 +4327,7 @@ namespace ts {
             result.containingType = containingType;
             result.declarations = declarations;
             result.isReadonly = isReadonly;
-            result.type = containingType.flags & TypeFlags.Union ? getUnionType(propTypes) : getIntersectionType(propTypes);
+            result.type = containingType.flags & TypeFlags.Union ? getUnionType(propTypes, /*noSubtypeReduction*/ true) : getIntersectionType(propTypes);
             return result;
         }
 
@@ -5148,7 +5148,8 @@ namespace ts {
                 if (type.flags & TypeFlags.Null) typeSet.containsNull = true;
                 if (!(type.flags & TypeFlags.ContainsWideningType)) typeSet.containsNonWideningType = true;
             }
-            else if (type !== neverType && !contains(typeSet, type)) {
+            else if (type !== neverType && !contains(typeSet, type) &&
+                !(type.flags & TypeFlags.Anonymous && type.symbol && type.symbol.flags & (SymbolFlags.Function | SymbolFlags.Method) && containsIdenticalType(typeSet, type))) {
                 typeSet.push(type);
             }
         }
@@ -5161,6 +5162,15 @@ namespace ts {
             }
         }
 
+        function containsIdenticalType(types: Type[], type: Type) {
+            for (const t of types) {
+                if (isTypeIdenticalTo(t, type)) {
+                    return true;
+                }
+            }
+            return false;
+        }
+
         function isSubtypeOfAny(candidate: Type, types: Type[]): boolean {
             for (let i = 0, len = types.length; i < len; i++) {
                 if (candidate !== types[i] && isTypeSubtypeOf(candidate, types[i])) {
diff --git a/src/harness/loggedIO.ts b/src/harness/loggedIO.ts
index 25e982cf680..33a46450a17 100644
--- a/src/harness/loggedIO.ts
+++ b/src/harness/loggedIO.ts
@@ -209,7 +209,7 @@ namespace Playback {
             memoize(path => findResultByFields(replayLog.pathsResolved, { path }, !ts.isRootedDiskPath(ts.normalizeSlashes(path)) && replayLog.currentDirectory ? replayLog.currentDirectory + "/" + path : ts.normalizeSlashes(path))));
 
         wrapper.readFile = recordReplay(wrapper.readFile, underlying)(
-            path => {
+            (path: string) => {
                 const result = underlying.readFile(path);
                 const logEntry = { path, codepage: 0, result: { contents: result, codepage: 0 } };
                 recordLog.filesRead.push(logEntry);