From 125dd57a757612367bcf495ed3070bb932ae75ed Mon Sep 17 00:00:00 2001
From: Nathan Shively-Sanders <nathansa@microsoft.com>
Date: Wed, 8 Feb 2017 13:28:23 -0800
Subject: [PATCH] Fix assigned type of assignment nested in literals

Fixes #12946
---
 src/compiler/checker.ts                       | 10 +++++-
 .../reference/assignmentNestedInLiterals.js   | 13 +++++++
 .../assignmentNestedInLiterals.symbols        | 25 +++++++++++++
 .../assignmentNestedInLiterals.types          | 35 +++++++++++++++++++
 .../compiler/assignmentNestedInLiterals.ts    |  6 ++++
 5 files changed, 88 insertions(+), 1 deletion(-)
 create mode 100644 tests/baselines/reference/assignmentNestedInLiterals.js
 create mode 100644 tests/baselines/reference/assignmentNestedInLiterals.symbols
 create mode 100644 tests/baselines/reference/assignmentNestedInLiterals.types
 create mode 100644 tests/cases/compiler/assignmentNestedInLiterals.ts

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 4423b574e3..428a4e6eee 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -9469,11 +9469,19 @@ namespace ts {
         }
 
         function getAssignedTypeOfBinaryExpression(node: BinaryExpression): Type {
-            return node.parent.kind === SyntaxKind.ArrayLiteralExpression || node.parent.kind === SyntaxKind.PropertyAssignment ?
+            const isDestructuringDefaultAssignment =
+                node.parent.kind === SyntaxKind.ArrayLiteralExpression && isDestructuringAssignmentTarget(node.parent) ||
+                node.parent.kind === SyntaxKind.PropertyAssignment && isDestructuringAssignmentTarget(node.parent.parent);
+            return isDestructuringDefaultAssignment ?
                 getTypeWithDefault(getAssignedType(node), node.right) :
                 getTypeOfExpression(node.right);
         }
 
+        function isDestructuringAssignmentTarget(parent: Node) {
+            return parent.parent.kind === SyntaxKind.BinaryExpression && (parent.parent as BinaryExpression).left === parent ||
+                parent.parent.kind === SyntaxKind.ForOfStatement && (parent.parent as ForOfStatement).initializer === parent;
+        }
+
         function getAssignedTypeOfArrayLiteralElement(node: ArrayLiteralExpression, element: Expression): Type {
             return getTypeOfDestructuredArrayElement(getAssignedType(node), indexOf(node.elements, element));
         }
diff --git a/tests/baselines/reference/assignmentNestedInLiterals.js b/tests/baselines/reference/assignmentNestedInLiterals.js
new file mode 100644
index 0000000000..cd4bc6c669
--- /dev/null
+++ b/tests/baselines/reference/assignmentNestedInLiterals.js
@@ -0,0 +1,13 @@
+//// [assignmentNestedInLiterals.ts]
+var target, x, y;
+target = [x = 1, y = x];
+
+var aegis, a, b;
+aegis = { x: a = 1, y: b = a };
+
+
+//// [assignmentNestedInLiterals.js]
+var target, x, y;
+target = [x = 1, y = x];
+var aegis, a, b;
+aegis = { x: a = 1, y: b = a };
diff --git a/tests/baselines/reference/assignmentNestedInLiterals.symbols b/tests/baselines/reference/assignmentNestedInLiterals.symbols
new file mode 100644
index 0000000000..90edd9ed04
--- /dev/null
+++ b/tests/baselines/reference/assignmentNestedInLiterals.symbols
@@ -0,0 +1,25 @@
+=== tests/cases/compiler/assignmentNestedInLiterals.ts ===
+var target, x, y;
+>target : Symbol(target, Decl(assignmentNestedInLiterals.ts, 0, 3))
+>x : Symbol(x, Decl(assignmentNestedInLiterals.ts, 0, 11))
+>y : Symbol(y, Decl(assignmentNestedInLiterals.ts, 0, 14))
+
+target = [x = 1, y = x];
+>target : Symbol(target, Decl(assignmentNestedInLiterals.ts, 0, 3))
+>x : Symbol(x, Decl(assignmentNestedInLiterals.ts, 0, 11))
+>y : Symbol(y, Decl(assignmentNestedInLiterals.ts, 0, 14))
+>x : Symbol(x, Decl(assignmentNestedInLiterals.ts, 0, 11))
+
+var aegis, a, b;
+>aegis : Symbol(aegis, Decl(assignmentNestedInLiterals.ts, 3, 3))
+>a : Symbol(a, Decl(assignmentNestedInLiterals.ts, 3, 10))
+>b : Symbol(b, Decl(assignmentNestedInLiterals.ts, 3, 13))
+
+aegis = { x: a = 1, y: b = a };
+>aegis : Symbol(aegis, Decl(assignmentNestedInLiterals.ts, 3, 3))
+>x : Symbol(x, Decl(assignmentNestedInLiterals.ts, 4, 9))
+>a : Symbol(a, Decl(assignmentNestedInLiterals.ts, 3, 10))
+>y : Symbol(y, Decl(assignmentNestedInLiterals.ts, 4, 19))
+>b : Symbol(b, Decl(assignmentNestedInLiterals.ts, 3, 13))
+>a : Symbol(a, Decl(assignmentNestedInLiterals.ts, 3, 10))
+
diff --git a/tests/baselines/reference/assignmentNestedInLiterals.types b/tests/baselines/reference/assignmentNestedInLiterals.types
new file mode 100644
index 0000000000..8c4d5aadc7
--- /dev/null
+++ b/tests/baselines/reference/assignmentNestedInLiterals.types
@@ -0,0 +1,35 @@
+=== tests/cases/compiler/assignmentNestedInLiterals.ts ===
+var target, x, y;
+>target : any
+>x : any
+>y : any
+
+target = [x = 1, y = x];
+>target = [x = 1, y = x] : number[]
+>target : any
+>[x = 1, y = x] : number[]
+>x = 1 : 1
+>x : any
+>1 : 1
+>y = x : number
+>y : any
+>x : number
+
+var aegis, a, b;
+>aegis : any
+>a : any
+>b : any
+
+aegis = { x: a = 1, y: b = a };
+>aegis = { x: a = 1, y: b = a } : { x: number; y: number; }
+>aegis : any
+>{ x: a = 1, y: b = a } : { x: number; y: number; }
+>x : number
+>a = 1 : 1
+>a : any
+>1 : 1
+>y : number
+>b = a : number
+>b : any
+>a : number
+
diff --git a/tests/cases/compiler/assignmentNestedInLiterals.ts b/tests/cases/compiler/assignmentNestedInLiterals.ts
new file mode 100644
index 0000000000..5b1f52cb45
--- /dev/null
+++ b/tests/cases/compiler/assignmentNestedInLiterals.ts
@@ -0,0 +1,6 @@
+// @noImplicitAny: true
+var target, x, y;
+target = [x = 1, y = x];
+
+var aegis, a, b;
+aegis = { x: a = 1, y: b = a };