Merge pull request #7555 from Microsoft/destructuring-variable-declarations

Destructuring in variable declarations when module kind is not ES6

Author: vladima

src/compiler/emitter.ts

@@ -4218,12 +4218,31 @@ var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, ge
 
             function emitVariableDeclaration(node: VariableDeclaration) {
                 if (isBindingPattern(node.name)) {
-                    if (languageVersion < ScriptTarget.ES6) {
-                        emitDestructuring(node, /*isAssignmentExpressionStatement*/ false);
-                    }
-                    else {
+                    const isExported = getCombinedNodeFlags(node) & NodeFlags.Export;
+                    if (languageVersion >= ScriptTarget.ES6 && (!isExported || modulekind === ModuleKind.ES6)) {
+                        // emit ES6 destructuring only if target module is ES6 or variable is not exported
+                        // exported variables in CJS/AMD are prefixed with 'exports.' so result javascript { exports.toString } = 1; is illegal
+
+                        const isTopLevelDeclarationInSystemModule =
+                            modulekind === ModuleKind.System &&
+                            shouldHoistVariable(node, /*checkIfSourceFileLevelDecl*/true);
+
+                        if (isTopLevelDeclarationInSystemModule) {
+                            // In System modules top level variables are hoisted
+                            // so variable declarations with destructuring are turned into destructuring assignments.
+                            // As a result, they will need parentheses to disambiguate object binding assignments from blocks.
+                            write("(");
+                        }
+
                         emit(node.name);
                         emitOptional(" = ", node.initializer);
+
+                        if (isTopLevelDeclarationInSystemModule) {
+                            write(")");
+                        }
+                    }
+                    else {
+                        emitDestructuring(node, /*isAssignmentExpressionStatement*/ false);
                     }
                 }
                 else {

tests/baselines/reference/destructuringInVariableDeclarations1.js

@@ -0,0 +1,13 @@
+//// [destructuringInVariableDeclarations1.ts]
+export let { toString } = 1;
+{
+    let { toFixed } = 1;
+}
+
+
+//// [destructuringInVariableDeclarations1.js]
+"use strict";
+exports.toString = (1).toString;
+{
+    let { toFixed } = 1;
+}

tests/baselines/reference/destructuringInVariableDeclarations1.symbols

@@ -0,0 +1,8 @@
+=== tests/cases/compiler/destructuringInVariableDeclarations1.ts ===
+export let { toString } = 1;
+>toString : Symbol(toString, Decl(destructuringInVariableDeclarations1.ts, 0, 12))
+{
+    let { toFixed } = 1;
+>toFixed : Symbol(toFixed, Decl(destructuringInVariableDeclarations1.ts, 2, 9))
+}
+

tests/baselines/reference/destructuringInVariableDeclarations1.types

@@ -0,0 +1,10 @@
+=== tests/cases/compiler/destructuringInVariableDeclarations1.ts ===
+export let { toString } = 1;
+>toString : (radix?: number) => string
+>1 : number
+{
+    let { toFixed } = 1;
+>toFixed : (fractionDigits?: number) => string
+>1 : number
+}
+

tests/baselines/reference/destructuringInVariableDeclarations2.js

@@ -0,0 +1,14 @@
+//// [destructuringInVariableDeclarations2.ts]
+let { toString } = 1;
+{
+    let { toFixed } = 1;
+}
+export {};
+
+
+//// [destructuringInVariableDeclarations2.js]
+"use strict";
+let { toString } = 1;
+{
+    let { toFixed } = 1;
+}

tests/baselines/reference/destructuringInVariableDeclarations2.symbols

@@ -0,0 +1,9 @@
+=== tests/cases/compiler/destructuringInVariableDeclarations2.ts ===
+let { toString } = 1;
+>toString : Symbol(toString, Decl(destructuringInVariableDeclarations2.ts, 0, 5))
+{
+    let { toFixed } = 1;
+>toFixed : Symbol(toFixed, Decl(destructuringInVariableDeclarations2.ts, 2, 9))
+}
+export {};
+

tests/baselines/reference/destructuringInVariableDeclarations2.types

@@ -0,0 +1,11 @@
+=== tests/cases/compiler/destructuringInVariableDeclarations2.ts ===
+let { toString } = 1;
+>toString : (radix?: number) => string
+>1 : number
+{
+    let { toFixed } = 1;
+>toFixed : (fractionDigits?: number) => string
+>1 : number
+}
+export {};
+

tests/baselines/reference/destructuringInVariableDeclarations3.js

@@ -0,0 +1,15 @@
+//// [destructuringInVariableDeclarations3.ts]
+export let { toString } = 1;
+{
+    let { toFixed } = 1;
+}
+
+
+//// [destructuringInVariableDeclarations3.js]
+define(["require", "exports"], function (require, exports) {
+    "use strict";
+    exports.toString = (1).toString;
+    {
+        let { toFixed } = 1;
+    }
+});

tests/baselines/reference/destructuringInVariableDeclarations3.symbols

@@ -0,0 +1,8 @@
+=== tests/cases/compiler/destructuringInVariableDeclarations3.ts ===
+export let { toString } = 1;
+>toString : Symbol(toString, Decl(destructuringInVariableDeclarations3.ts, 0, 12))
+{
+    let { toFixed } = 1;
+>toFixed : Symbol(toFixed, Decl(destructuringInVariableDeclarations3.ts, 2, 9))
+}
+

tests/baselines/reference/destructuringInVariableDeclarations3.types

@@ -0,0 +1,10 @@
+=== tests/cases/compiler/destructuringInVariableDeclarations3.ts ===
+export let { toString } = 1;
+>toString : (radix?: number) => string
+>1 : number
+{
+    let { toFixed } = 1;
+>toFixed : (fractionDigits?: number) => string
+>1 : number
+}
+

tests/baselines/reference/destructuringInVariableDeclarations4.js

@@ -0,0 +1,16 @@
+//// [destructuringInVariableDeclarations4.ts]
+let { toString } = 1;
+{
+    let { toFixed } = 1;
+}
+export {};
+
+
+//// [destructuringInVariableDeclarations4.js]
+define(["require", "exports"], function (require, exports) {
+    "use strict";
+    let { toString } = 1;
+    {
+        let { toFixed } = 1;
+    }
+});

tests/baselines/reference/destructuringInVariableDeclarations4.symbols

@@ -0,0 +1,9 @@
+=== tests/cases/compiler/destructuringInVariableDeclarations4.ts ===
+let { toString } = 1;
+>toString : Symbol(toString, Decl(destructuringInVariableDeclarations4.ts, 0, 5))
+{
+    let { toFixed } = 1;
+>toFixed : Symbol(toFixed, Decl(destructuringInVariableDeclarations4.ts, 2, 9))
+}
+export {};
+

tests/baselines/reference/destructuringInVariableDeclarations4.types

@@ -0,0 +1,11 @@
+=== tests/cases/compiler/destructuringInVariableDeclarations4.ts ===
+let { toString } = 1;
+>toString : (radix?: number) => string
+>1 : number
+{
+    let { toFixed } = 1;
+>toFixed : (fractionDigits?: number) => string
+>1 : number
+}
+export {};
+

tests/baselines/reference/destructuringInVariableDeclarations5.js

@@ -0,0 +1,22 @@
+//// [destructuringInVariableDeclarations5.ts]
+export let { toString } = 1;
+{
+    let { toFixed } = 1;
+}
+
+
+//// [destructuringInVariableDeclarations5.js]
+(function (factory) {
+    if (typeof module === 'object' && typeof module.exports === 'object') {
+        var v = factory(require, exports); if (v !== undefined) module.exports = v;
+    }
+    else if (typeof define === 'function' && define.amd) {
+        define(["require", "exports"], factory);
+    }
+})(function (require, exports) {
+    "use strict";
+    exports.toString = (1).toString;
+    {
+        let { toFixed } = 1;
+    }
+});

tests/baselines/reference/destructuringInVariableDeclarations5.symbols

@@ -0,0 +1,8 @@
+=== tests/cases/compiler/destructuringInVariableDeclarations5.ts ===
+export let { toString } = 1;
+>toString : Symbol(toString, Decl(destructuringInVariableDeclarations5.ts, 0, 12))
+{
+    let { toFixed } = 1;
+>toFixed : Symbol(toFixed, Decl(destructuringInVariableDeclarations5.ts, 2, 9))
+}
+

tests/baselines/reference/destructuringInVariableDeclarations5.types

@@ -0,0 +1,10 @@
+=== tests/cases/compiler/destructuringInVariableDeclarations5.ts ===
+export let { toString } = 1;
+>toString : (radix?: number) => string
+>1 : number
+{
+    let { toFixed } = 1;
+>toFixed : (fractionDigits?: number) => string
+>1 : number
+}
+

tests/baselines/reference/destructuringInVariableDeclarations6.js

@@ -0,0 +1,23 @@
+//// [destructuringInVariableDeclarations6.ts]
+let { toString } = 1;
+{
+    let { toFixed } = 1;
+}
+export {};
+
+
+//// [destructuringInVariableDeclarations6.js]
+(function (factory) {
+    if (typeof module === 'object' && typeof module.exports === 'object') {
+        var v = factory(require, exports); if (v !== undefined) module.exports = v;
+    }
+    else if (typeof define === 'function' && define.amd) {
+        define(["require", "exports"], factory);
+    }
+})(function (require, exports) {
+    "use strict";
+    let { toString } = 1;
+    {
+        let { toFixed } = 1;
+    }
+});

tests/baselines/reference/destructuringInVariableDeclarations6.symbols

@@ -0,0 +1,9 @@
+=== tests/cases/compiler/destructuringInVariableDeclarations6.ts ===
+let { toString } = 1;
+>toString : Symbol(toString, Decl(destructuringInVariableDeclarations6.ts, 0, 5))
+{
+    let { toFixed } = 1;
+>toFixed : Symbol(toFixed, Decl(destructuringInVariableDeclarations6.ts, 2, 9))
+}
+export {};
+

tests/baselines/reference/destructuringInVariableDeclarations6.types

@@ -0,0 +1,11 @@
+=== tests/cases/compiler/destructuringInVariableDeclarations6.ts ===
+let { toString } = 1;
+>toString : (radix?: number) => string
+>1 : number
+{
+    let { toFixed } = 1;
+>toFixed : (fractionDigits?: number) => string
+>1 : number
+}
+export {};
+

tests/baselines/reference/destructuringInVariableDeclarations7.js

@@ -0,0 +1,22 @@
+//// [destructuringInVariableDeclarations7.ts]
+export let { toString } = 1;
+{
+    let { toFixed } = 1;
+}
+
+
+//// [destructuringInVariableDeclarations7.js]
+System.register([], function(exports_1, context_1) {
+    "use strict";
+    var __moduleName = context_1 && context_1.id;
+    var toString;
+    return {
+        setters:[],
+        execute: function() {
+            exports_1("toString", toString = (1).toString);
+            {
+                let { toFixed } = 1;
+            }
+        }
+    }
+});

tests/baselines/reference/destructuringInVariableDeclarations7.symbols

@@ -0,0 +1,8 @@
+=== tests/cases/compiler/destructuringInVariableDeclarations7.ts ===
+export let { toString } = 1;
+>toString : Symbol(toString, Decl(destructuringInVariableDeclarations7.ts, 0, 12))
+{
+    let { toFixed } = 1;
+>toFixed : Symbol(toFixed, Decl(destructuringInVariableDeclarations7.ts, 2, 9))
+}
+

tests/baselines/reference/destructuringInVariableDeclarations7.types

@@ -0,0 +1,10 @@
+=== tests/cases/compiler/destructuringInVariableDeclarations7.ts ===
+export let { toString } = 1;
+>toString : (radix?: number) => string
+>1 : number
+{
+    let { toFixed } = 1;
+>toFixed : (fractionDigits?: number) => string
+>1 : number
+}
+

tests/baselines/reference/destructuringInVariableDeclarations8.js

@@ -0,0 +1,23 @@
+//// [destructuringInVariableDeclarations8.ts]
+let { toString } = 1;
+{
+    let { toFixed } = 1;
+}
+export {};
+
+
+//// [destructuringInVariableDeclarations8.js]
+System.register([], function(exports_1, context_1) {
+    "use strict";
+    var __moduleName = context_1 && context_1.id;
+    var toString;
+    return {
+        setters:[],
+        execute: function() {
+            ({ toString } = 1);
+            {
+                let { toFixed } = 1;
+            }
+        }
+    }
+});

tests/baselines/reference/destructuringInVariableDeclarations8.symbols

@@ -0,0 +1,9 @@
+=== tests/cases/compiler/destructuringInVariableDeclarations8.ts ===
+let { toString } = 1;
+>toString : Symbol(toString, Decl(destructuringInVariableDeclarations8.ts, 0, 5))
+{
+    let { toFixed } = 1;
+>toFixed : Symbol(toFixed, Decl(destructuringInVariableDeclarations8.ts, 2, 9))
+}
+export {};
+

tests/baselines/reference/destructuringInVariableDeclarations8.types

@@ -0,0 +1,11 @@
+=== tests/cases/compiler/destructuringInVariableDeclarations8.ts ===
+let { toString } = 1;
+>toString : (radix?: number) => string
+>1 : number
+{
+    let { toFixed } = 1;
+>toFixed : (fractionDigits?: number) => string
+>1 : number
+}
+export {};
+

tests/cases/compiler/destructuringInVariableDeclarations1.ts

@@ -0,0 +1,6 @@
+// @target: es6
+// @module: commonjs
+export let { toString } = 1;
+{
+    let { toFixed } = 1;
+}

tests/cases/compiler/destructuringInVariableDeclarations2.ts

@@ -0,0 +1,7 @@
+// @target: es6
+// @module: commonjs
+let { toString } = 1;
+{
+    let { toFixed } = 1;
+}
+export {};

tests/cases/compiler/destructuringInVariableDeclarations3.ts

@@ -0,0 +1,6 @@
+// @target: es6
+// @module: amd
+export let { toString } = 1;
+{
+    let { toFixed } = 1;
+}

tests/cases/compiler/destructuringInVariableDeclarations4.ts

@@ -0,0 +1,7 @@
+// @target: es6
+// @module: amd
+let { toString } = 1;
+{
+    let { toFixed } = 1;
+}
+export {};

tests/cases/compiler/destructuringInVariableDeclarations5.ts

@@ -0,0 +1,6 @@
+// @target: es6
+// @module: umd
+export let { toString } = 1;
+{
+    let { toFixed } = 1;
+}