From 03653934c30f4bc3a94f7067ff8506fcdfa37048 Mon Sep 17 00:00:00 2001
From: Nathan Shively-Sanders <293473+sandersn@users.noreply.github.com>
Date: Thu, 23 Aug 2018 08:21:28 -0700
Subject: [PATCH] Don't create expando object literals in TS (#26525)

Previously, getWidenedTypedFromJSPropertyAssignment was not called for
Typescript code. Since property assignments on functions, it is. That
meant that property assignments would incorrectly create a JS container
for empty object literals in a property assignment, even in Typescript:

```ts
const one = () => 1
one.p = {}
one.p.q = {} // should not work in Typescript!
```

Now empty object literals never create expando objects in Typescript,
because getJSExpandoObjectType requires the declaration to be in a JS
file.
---
 src/compiler/checker.ts                       |  2 +-
 .../reference/typeFromPropertyAssignment30.js | 15 +++++++++++++
 .../typeFromPropertyAssignment30.symbols      | 20 ++++++++++++++++++
 .../typeFromPropertyAssignment30.types        | 21 +++++++++++++++++++
 .../salsa/typeFromPropertyAssignment30.ts     |  8 +++++++
 5 files changed, 65 insertions(+), 1 deletion(-)
 create mode 100644 tests/baselines/reference/typeFromPropertyAssignment30.js
 create mode 100644 tests/baselines/reference/typeFromPropertyAssignment30.symbols
 create mode 100644 tests/baselines/reference/typeFromPropertyAssignment30.types
 create mode 100644 tests/cases/conformance/salsa/typeFromPropertyAssignment30.ts

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 7e0e7122404..269f8b26f0a 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -4795,7 +4795,7 @@ namespace ts {
         }
 
         function getJSExpandoObjectType(decl: Node, symbol: Symbol, init: Expression | undefined): Type | undefined {
-            if (!init || !isObjectLiteralExpression(init) || init.properties.length) {
+            if (!isInJavaScriptFile(decl) || !init || !isObjectLiteralExpression(init) || init.properties.length) {
                 return undefined;
             }
             const exports = createSymbolTable();
diff --git a/tests/baselines/reference/typeFromPropertyAssignment30.js b/tests/baselines/reference/typeFromPropertyAssignment30.js
new file mode 100644
index 00000000000..1ec7cf70a8b
--- /dev/null
+++ b/tests/baselines/reference/typeFromPropertyAssignment30.js
@@ -0,0 +1,15 @@
+//// [typeFromPropertyAssignment30.ts]
+interface Combo {
+    (): number;
+    p?: { [s: string]: number };
+}
+const c: Combo = () => 1
+// should not be an expando object, but contextually typed by Combo.p
+c.p = {}
+
+
+
+//// [typeFromPropertyAssignment30.js]
+var c = function () { return 1; };
+// should not be an expando object, but contextually typed by Combo.p
+c.p = {};
diff --git a/tests/baselines/reference/typeFromPropertyAssignment30.symbols b/tests/baselines/reference/typeFromPropertyAssignment30.symbols
new file mode 100644
index 00000000000..5614067864c
--- /dev/null
+++ b/tests/baselines/reference/typeFromPropertyAssignment30.symbols
@@ -0,0 +1,20 @@
+=== tests/cases/conformance/salsa/typeFromPropertyAssignment30.ts ===
+interface Combo {
+>Combo : Symbol(Combo, Decl(typeFromPropertyAssignment30.ts, 0, 0))
+
+    (): number;
+    p?: { [s: string]: number };
+>p : Symbol(Combo.p, Decl(typeFromPropertyAssignment30.ts, 1, 15))
+>s : Symbol(s, Decl(typeFromPropertyAssignment30.ts, 2, 11))
+}
+const c: Combo = () => 1
+>c : Symbol(c, Decl(typeFromPropertyAssignment30.ts, 4, 5), Decl(typeFromPropertyAssignment30.ts, 4, 24))
+>Combo : Symbol(Combo, Decl(typeFromPropertyAssignment30.ts, 0, 0))
+
+// should not be an expando object, but contextually typed by Combo.p
+c.p = {}
+>c.p : Symbol(Combo.p, Decl(typeFromPropertyAssignment30.ts, 1, 15))
+>c : Symbol(c, Decl(typeFromPropertyAssignment30.ts, 4, 5), Decl(typeFromPropertyAssignment30.ts, 4, 24))
+>p : Symbol(Combo.p, Decl(typeFromPropertyAssignment30.ts, 1, 15))
+
+
diff --git a/tests/baselines/reference/typeFromPropertyAssignment30.types b/tests/baselines/reference/typeFromPropertyAssignment30.types
new file mode 100644
index 00000000000..ee2c9fdb8c5
--- /dev/null
+++ b/tests/baselines/reference/typeFromPropertyAssignment30.types
@@ -0,0 +1,21 @@
+=== tests/cases/conformance/salsa/typeFromPropertyAssignment30.ts ===
+interface Combo {
+    (): number;
+    p?: { [s: string]: number };
+>p : { [s: string]: number; }
+>s : string
+}
+const c: Combo = () => 1
+>c : Combo
+>() => 1 : { (): number; p: {}; }
+>1 : 1
+
+// should not be an expando object, but contextually typed by Combo.p
+c.p = {}
+>c.p = {} : {}
+>c.p : { [s: string]: number; }
+>c : Combo
+>p : { [s: string]: number; }
+>{} : {}
+
+
diff --git a/tests/cases/conformance/salsa/typeFromPropertyAssignment30.ts b/tests/cases/conformance/salsa/typeFromPropertyAssignment30.ts
new file mode 100644
index 00000000000..e24c8ec2b94
--- /dev/null
+++ b/tests/cases/conformance/salsa/typeFromPropertyAssignment30.ts
@@ -0,0 +1,8 @@
+interface Combo {
+    (): number;
+    p?: { [s: string]: number };
+}
+const c: Combo = () => 1
+// should not be an expando object, but contextually typed by Combo.p
+c.p = {}
+