From 861617006046bbd9b687f584eb09b46124ec30a5 Mon Sep 17 00:00:00 2001
From: Nathan Shively-Sanders <293473+sandersn@users.noreply.github.com>
Date: Wed, 3 Jan 2018 15:49:09 -0800
Subject: [PATCH] Fix printing of deferred mapped types

A deferred mapped type with a source that has an index signature now
prints {} as the type of the index signature. This avoids an infinite
recursion.
---
 src/compiler/checker.ts | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 2e7f1f0186f..770a31e9435 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -2860,8 +2860,11 @@ namespace ts {
                     for (const signature of resolvedType.constructSignatures) {
                         typeElements.push(<ConstructSignatureDeclaration>signatureToSignatureDeclarationHelper(signature, SyntaxKind.ConstructSignature, context));
                     }
-                    if (resolvedType.stringIndexInfo) {
-                        typeElements.push(indexInfoToIndexSignatureDeclarationHelper(resolvedType.stringIndexInfo, IndexKind.String, context));
+                    if (resolvedType.stringIndexInfo && !(resolvedType.objectFlags & ObjectFlags.Deferred)) {
+                        const indexInfo = resolvedType.objectFlags & ObjectFlags.Deferred ?
+                            createIndexInfo(emptyObjectType, resolvedType.stringIndexInfo.isReadonly, resolvedType.stringIndexInfo.declaration) :
+                            resolvedType.stringIndexInfo;
+                        typeElements.push(indexInfoToIndexSignatureDeclarationHelper(indexInfo, IndexKind.String, context));
                     }
                     if (resolvedType.numberIndexInfo) {
                         typeElements.push(indexInfoToIndexSignatureDeclarationHelper(resolvedType.numberIndexInfo, IndexKind.Number, context));