Only emit the RHS in an empty assignment pattern.

Author: DanielRosenwasser

src/compiler/emitter.ts

@@ -3249,7 +3249,11 @@ var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, Promi
                 function emitAssignmentExpression(root: BinaryExpression) {
                     let target = root.left;
                     let value = root.right;
-                    if (isAssignmentExpressionStatement) {
+
+                    if (isEmptyObjectLiteralOrArrayLiteral(target)) {
+                        emit(value);
+                    }
+                    else if (isAssignmentExpressionStatement) {
                         emitDestructuringAssignment(target, value);
                     }
                     else {

src/compiler/utilities.ts

@@ -1981,6 +1981,17 @@ namespace ts {
             (node.parent.kind === SyntaxKind.PropertyAccessExpression && (<PropertyAccessExpression>node.parent).name === node);
     }
 
+    export function isEmptyObjectLiteralOrArrayLiteral(expression: Node): boolean {
+        let kind = expression.kind;
+        if (kind === SyntaxKind.ObjectLiteralExpression) {
+            return (<ObjectLiteralExpression>expression).properties.length === 0;
+        }
+        if (kind === SyntaxKind.ArrayLiteralExpression) {
+            return (<ArrayLiteralExpression>expression).elements.length === 0;
+        }
+        return false;
+    }
+
     export function getLocalSymbolForExportDefault(symbol: Symbol) {
         return symbol && symbol.valueDeclaration && (symbol.valueDeclaration.flags & NodeFlags.Default) ? symbol.valueDeclaration.localSymbol : undefined;
     }