From 09761b5f075f3947a719151dddfd3a071fe3d857 Mon Sep 17 00:00:00 2001
From: Ron Buckton <rbuckton@microsoft.com>
Date: Thu, 8 Dec 2016 13:43:32 -0800
Subject: [PATCH] Fix error on extends in declaration file with importHelpers

---
 src/compiler/checker.ts                                  | 2 +-
 .../reference/importHelpersDeclarations.symbols          | 8 ++++++++
 .../baselines/reference/importHelpersDeclarations.types  | 8 ++++++++
 tests/cases/compiler/importHelpersDeclarations.ts        | 9 +++++++++
 4 files changed, 26 insertions(+), 1 deletion(-)
 create mode 100644 tests/baselines/reference/importHelpersDeclarations.symbols
 create mode 100644 tests/baselines/reference/importHelpersDeclarations.types
 create mode 100644 tests/cases/compiler/importHelpersDeclarations.ts

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 778e31b9c5b..de9011c9dbd 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -17999,7 +17999,7 @@ namespace ts {
 
             const baseTypeNode = getClassExtendsHeritageClauseElement(node);
             if (baseTypeNode) {
-                if (languageVersion < ScriptTarget.ES2015) {
+                if (languageVersion < ScriptTarget.ES2015 && !isInAmbientContext(node)) {
                     checkExternalEmitHelpers(baseTypeNode.parent, ExternalEmitHelpers.Extends);
                 }
 
diff --git a/tests/baselines/reference/importHelpersDeclarations.symbols b/tests/baselines/reference/importHelpersDeclarations.symbols
new file mode 100644
index 00000000000..f578850cc4e
--- /dev/null
+++ b/tests/baselines/reference/importHelpersDeclarations.symbols
@@ -0,0 +1,8 @@
+=== tests/cases/compiler/declaration.d.ts ===
+export declare class D {
+>D : Symbol(D, Decl(declaration.d.ts, 0, 0))
+}
+export declare class E extends D {
+>E : Symbol(E, Decl(declaration.d.ts, 1, 1))
+>D : Symbol(D, Decl(declaration.d.ts, 0, 0))
+}
diff --git a/tests/baselines/reference/importHelpersDeclarations.types b/tests/baselines/reference/importHelpersDeclarations.types
new file mode 100644
index 00000000000..4b8c56d7869
--- /dev/null
+++ b/tests/baselines/reference/importHelpersDeclarations.types
@@ -0,0 +1,8 @@
+=== tests/cases/compiler/declaration.d.ts ===
+export declare class D {
+>D : D
+}
+export declare class E extends D {
+>E : E
+>D : D
+}
diff --git a/tests/cases/compiler/importHelpersDeclarations.ts b/tests/cases/compiler/importHelpersDeclarations.ts
new file mode 100644
index 00000000000..7b958cda789
--- /dev/null
+++ b/tests/cases/compiler/importHelpersDeclarations.ts
@@ -0,0 +1,9 @@
+// @importHelpers: true
+// @target: es5
+// @module: commonjs
+// @moduleResolution: classic
+// @filename: declaration.d.ts
+export declare class D {
+}
+export declare class E extends D {
+}
\ No newline at end of file