From 40222d1a77a32ae412df8bda49f7ff20cfd8c3ba Mon Sep 17 00:00:00 2001
From: Wesley Wigham <wwigham@gmail.com>
Date: Mon, 16 Oct 2017 12:57:23 -0700
Subject: [PATCH] Fix for-in emit under systemjs (#19223)

---
 src/compiler/transformers/module/system.ts    |  5 ++++-
 .../reference/systemJsForInNoException.js     | 19 ++++++++++++++++++
 .../systemJsForInNoException.symbols          | 16 +++++++++++++++
 .../reference/systemJsForInNoException.types  | 20 +++++++++++++++++++
 .../compiler/systemJsForInNoException.ts      |  5 +++++
 5 files changed, 64 insertions(+), 1 deletion(-)
 create mode 100644 tests/baselines/reference/systemJsForInNoException.js
 create mode 100644 tests/baselines/reference/systemJsForInNoException.symbols
 create mode 100644 tests/baselines/reference/systemJsForInNoException.types
 create mode 100644 tests/cases/compiler/systemJsForInNoException.ts

diff --git a/src/compiler/transformers/module/system.ts b/src/compiler/transformers/module/system.ts
index ed943eb90ce..d674546efb9 100644
--- a/src/compiler/transformers/module/system.ts
+++ b/src/compiler/transformers/module/system.ts
@@ -826,7 +826,7 @@ namespace ts {
                     /*needsValue*/ false,
                     createAssignment
                 )
-                : createAssignment(node.name, visitNode(node.initializer, destructuringAndImportCallVisitor, isExpression));
+                : node.initializer ? createAssignment(node.name, visitNode(node.initializer, destructuringAndImportCallVisitor, isExpression)) : node.name;
         }
 
         /**
@@ -1296,6 +1296,9 @@ namespace ts {
                 let expressions: Expression[];
                 for (const variable of node.declarations) {
                     expressions = append(expressions, transformInitializedVariable(variable, /*isExportedDeclaration*/ false));
+                    if (!variable.initializer) {
+                        hoistBindingElement(variable);
+                    }
                 }
 
                 return expressions ? inlineExpressions(expressions) : createOmittedExpression();
diff --git a/tests/baselines/reference/systemJsForInNoException.js b/tests/baselines/reference/systemJsForInNoException.js
new file mode 100644
index 00000000000..2ac31e18416
--- /dev/null
+++ b/tests/baselines/reference/systemJsForInNoException.js
@@ -0,0 +1,19 @@
+//// [systemJsForInNoException.ts]
+export const obj = { a: 1 };
+for (var key in obj)
+    console.log(obj[key]);
+
+//// [systemJsForInNoException.js]
+System.register([], function (exports_1, context_1) {
+    "use strict";
+    var __moduleName = context_1 && context_1.id;
+    var obj, key;
+    return {
+        setters: [],
+        execute: function () {
+            exports_1("obj", obj = { a: 1 });
+            for (key in obj)
+                console.log(obj[key]);
+        }
+    };
+});
diff --git a/tests/baselines/reference/systemJsForInNoException.symbols b/tests/baselines/reference/systemJsForInNoException.symbols
new file mode 100644
index 00000000000..4d4d2e0206c
--- /dev/null
+++ b/tests/baselines/reference/systemJsForInNoException.symbols
@@ -0,0 +1,16 @@
+=== tests/cases/compiler/systemJsForInNoException.ts ===
+export const obj = { a: 1 };
+>obj : Symbol(obj, Decl(systemJsForInNoException.ts, 0, 12))
+>a : Symbol(a, Decl(systemJsForInNoException.ts, 0, 20))
+
+for (var key in obj)
+>key : Symbol(key, Decl(systemJsForInNoException.ts, 1, 8))
+>obj : Symbol(obj, Decl(systemJsForInNoException.ts, 0, 12))
+
+    console.log(obj[key]);
+>console.log : Symbol(Console.log, Decl(lib.dom.d.ts, --, --))
+>console : Symbol(console, Decl(lib.dom.d.ts, --, --))
+>log : Symbol(Console.log, Decl(lib.dom.d.ts, --, --))
+>obj : Symbol(obj, Decl(systemJsForInNoException.ts, 0, 12))
+>key : Symbol(key, Decl(systemJsForInNoException.ts, 1, 8))
+
diff --git a/tests/baselines/reference/systemJsForInNoException.types b/tests/baselines/reference/systemJsForInNoException.types
new file mode 100644
index 00000000000..6d9dbbb6e7b
--- /dev/null
+++ b/tests/baselines/reference/systemJsForInNoException.types
@@ -0,0 +1,20 @@
+=== tests/cases/compiler/systemJsForInNoException.ts ===
+export const obj = { a: 1 };
+>obj : { a: number; }
+>{ a: 1 } : { a: number; }
+>a : number
+>1 : 1
+
+for (var key in obj)
+>key : string
+>obj : { a: number; }
+
+    console.log(obj[key]);
+>console.log(obj[key]) : void
+>console.log : (message?: any, ...optionalParams: any[]) => void
+>console : Console
+>log : (message?: any, ...optionalParams: any[]) => void
+>obj[key] : any
+>obj : { a: number; }
+>key : string
+
diff --git a/tests/cases/compiler/systemJsForInNoException.ts b/tests/cases/compiler/systemJsForInNoException.ts
new file mode 100644
index 00000000000..e35c3aa24a3
--- /dev/null
+++ b/tests/cases/compiler/systemJsForInNoException.ts
@@ -0,0 +1,5 @@
+// @module: system
+// @lib: es6,dom
+export const obj = { a: 1 };
+for (var key in obj)
+    console.log(obj[key]);
\ No newline at end of file