Allow destructuring in ambient

src/compiler/checker.ts

@@ -12173,9 +12173,6 @@ module ts {
         function checkGrammarVariableDeclaration(node: VariableDeclaration) {
             if (node.parent.parent.kind !== SyntaxKind.ForInStatement && node.parent.parent.kind !== SyntaxKind.ForOfStatement) {
                 if (isInAmbientContext(node)) {
-                    if (isBindingPattern(node.name)) {
-                        return grammarErrorOnNode(node, Diagnostics.Destructuring_declarations_are_not_allowed_in_ambient_contexts);
-                    }
                     if (node.initializer) {
                         // Error on equals token which immediate precedes the initializer
                         let equalsTokenLength = "=".length;

src/compiler/declarationEmitter.ts

@@ -993,7 +993,18 @@ module ts {
             }
 
             function emitBindingPattern(bindingPattern: BindingPattern) {
-                emitCommaList(bindingPattern.elements, emitBindingElement);
+                // Only select non-omitted expression from the bindingPattern's elements.
+                // We have to do this to avoid emitting trailing commas.
+                // For example:
+                //      original: var [, c,,] = [ 2,3,4]
+                //      emitted: declare var c: number; // instead of declare var c:number, ;
+                let elements: Node[] = [];
+                for (let element of bindingPattern.elements) {
+                    if (element.kind !== SyntaxKind.OmittedExpression){
+                        elements.push(element);
+                    }
+                }
+                emitCommaList(elements, emitBindingElement);
             }
 
             function emitBindingElement(bindingElement: BindingElement) {
@@ -1291,7 +1302,10 @@ module ts {
                 write("...");
             }
             if (isBindingPattern(node.name)) {
-                write("_" + indexOf((<FunctionLikeDeclaration>node.parent).parameters, node));
+                // For bindingPattern, we can't simply writeTextOfNode from the source file
+                // because we want to omit the initializer and using writeTextOfNode will result in initializer get emitted.
+                // Therefore, we will have to recursively emit each element in the bindingPattern.
+                emitBindingPattern(<BindingPattern>node.name);
             }
             else {
                 writeTextOfNode(currentSourceFile, node.name);
@@ -1311,72 +1325,146 @@ module ts {
             }
 
             function getParameterDeclarationTypeVisibilityError(symbolAccesibilityResult: SymbolAccessiblityResult): SymbolAccessibilityDiagnostic {
-                let diagnosticMessage: DiagnosticMessage;
+                let diagnosticMessage: DiagnosticMessage = getParameterDeclarationTypeVisibilityDiagnosticMessage(symbolAccesibilityResult);
+                return diagnosticMessage !== undefined ? {
+                    diagnosticMessage,
+                    errorNode: node,
+                    typeName: node.name
+                } : undefined;
+            }
+
+            function getParameterDeclarationTypeVisibilityDiagnosticMessage(symbolAccesibilityResult: SymbolAccessiblityResult): DiagnosticMessage {
                 switch (node.parent.kind) {
                     case SyntaxKind.Constructor:
-                        diagnosticMessage = symbolAccesibilityResult.errorModuleName ?
+                        return symbolAccesibilityResult.errorModuleName ?
                             symbolAccesibilityResult.accessibility === SymbolAccessibility.CannotBeNamed ?
                                 Diagnostics.Parameter_0_of_constructor_from_exported_class_has_or_is_using_name_1_from_external_module_2_but_cannot_be_named :
                                 Diagnostics.Parameter_0_of_constructor_from_exported_class_has_or_is_using_name_1_from_private_module_2 :
                             Diagnostics.Parameter_0_of_constructor_from_exported_class_has_or_is_using_private_name_1;
-                        break;
 
                     case SyntaxKind.ConstructSignature:
                         // Interfaces cannot have parameter types that cannot be named
-                        diagnosticMessage = symbolAccesibilityResult.errorModuleName ?
+                        return symbolAccesibilityResult.errorModuleName ?
                             Diagnostics.Parameter_0_of_constructor_signature_from_exported_interface_has_or_is_using_name_1_from_private_module_2 :
                             Diagnostics.Parameter_0_of_constructor_signature_from_exported_interface_has_or_is_using_private_name_1;
-                        break;
 
                     case SyntaxKind.CallSignature:
                         // Interfaces cannot have parameter types that cannot be named
-                        diagnosticMessage = symbolAccesibilityResult.errorModuleName ?
+                        return symbolAccesibilityResult.errorModuleName ?
                             Diagnostics.Parameter_0_of_call_signature_from_exported_interface_has_or_is_using_name_1_from_private_module_2 :
                             Diagnostics.Parameter_0_of_call_signature_from_exported_interface_has_or_is_using_private_name_1;
-                        break;
 
                     case SyntaxKind.MethodDeclaration:
                     case SyntaxKind.MethodSignature:
                         if (node.parent.flags & NodeFlags.Static) {
-                            diagnosticMessage = symbolAccesibilityResult.errorModuleName ?
+                            return symbolAccesibilityResult.errorModuleName ?
                                 symbolAccesibilityResult.accessibility === SymbolAccessibility.CannotBeNamed ?
                                     Diagnostics.Parameter_0_of_public_static_method_from_exported_class_has_or_is_using_name_1_from_external_module_2_but_cannot_be_named :
                                     Diagnostics.Parameter_0_of_public_static_method_from_exported_class_has_or_is_using_name_1_from_private_module_2 :
                                 Diagnostics.Parameter_0_of_public_static_method_from_exported_class_has_or_is_using_private_name_1;
                         }
                         else if (node.parent.parent.kind === SyntaxKind.ClassDeclaration) {
-                            diagnosticMessage = symbolAccesibilityResult.errorModuleName ?
+                             return symbolAccesibilityResult.errorModuleName ?
                                 symbolAccesibilityResult.accessibility === SymbolAccessibility.CannotBeNamed ?
                                     Diagnostics.Parameter_0_of_public_method_from_exported_class_has_or_is_using_name_1_from_external_module_2_but_cannot_be_named :
                                     Diagnostics.Parameter_0_of_public_method_from_exported_class_has_or_is_using_name_1_from_private_module_2 :
                                 Diagnostics.Parameter_0_of_public_method_from_exported_class_has_or_is_using_private_name_1;
                         }
                         else {
                             // Interfaces cannot have parameter types that cannot be named
-                            diagnosticMessage = symbolAccesibilityResult.errorModuleName ?
+                            return symbolAccesibilityResult.errorModuleName ?
                                 Diagnostics.Parameter_0_of_method_from_exported_interface_has_or_is_using_name_1_from_private_module_2 :
                                 Diagnostics.Parameter_0_of_method_from_exported_interface_has_or_is_using_private_name_1;
                         }
-                        break;
 
                     case SyntaxKind.FunctionDeclaration:
-                        diagnosticMessage = symbolAccesibilityResult.errorModuleName ?
+                        return symbolAccesibilityResult.errorModuleName ?
                             symbolAccesibilityResult.accessibility === SymbolAccessibility.CannotBeNamed ?
                                 Diagnostics.Parameter_0_of_exported_function_has_or_is_using_name_1_from_external_module_2_but_cannot_be_named :
                                 Diagnostics.Parameter_0_of_exported_function_has_or_is_using_name_1_from_private_module_2 :
                             Diagnostics.Parameter_0_of_exported_function_has_or_is_using_private_name_1;
-                        break;
 
                     default:
                         Debug.fail("This is unknown parent for parameter: " + node.parent.kind);
                 }
+            }
 
-                return {
-                    diagnosticMessage,
-                    errorNode: node,
-                    typeName: node.name
-                };
+            function emitBindingPattern(bindingPattern: BindingPattern) {
+                // We have to explicitly emit square bracket and bracket because these tokens are not store inside the node.
+                if (bindingPattern.kind === SyntaxKind.ObjectBindingPattern) {
+                    write("{");
+                    emitCommaList(bindingPattern.elements, emitBindingElement);
+                    write("}");
+                }
+                else if (bindingPattern.kind === SyntaxKind.ArrayBindingPattern) {
+                    write("[");
+                    let elements = bindingPattern.elements;
+                    emitCommaList(elements, emitBindingElement);
+                    if (elements && elements.hasTrailingComma) {
+                        write(", ");
+                    }
+                    write("]");
+                }
             }
+
+            function emitBindingElement(bindingElement: BindingElement) {
+                function getBindingElementTypeVisibilityError(symbolAccesibilityResult: SymbolAccessiblityResult): SymbolAccessibilityDiagnostic {
+                    let diagnosticMessage = getParameterDeclarationTypeVisibilityDiagnosticMessage(symbolAccesibilityResult);
+                    return diagnosticMessage !== undefined ? {
+                        diagnosticMessage,
+                        errorNode: bindingElement,
+                        typeName: bindingElement.name
+                    } : undefined;
+                }
+
+                if (bindingElement.kind === SyntaxKind.OmittedExpression) {
+                    // If bindingElement is an omittedExpression (i.e. containing elision),
+                    // we will emit blank space (although this may differ from users' original code,
+                    // it allows emitSeparatedList to write separator appropriately)
+                    // Example:
+                    //      original: function foo([, x, ,]) {}
+                    //      emit    : function foo([ , x,  , ]) {}
+                    write(" ");
+                }
+                else if (bindingElement.kind === SyntaxKind.BindingElement) {
+                    if (bindingElement.propertyName) {
+                        // bindingElement has propertyName property in the following case:
+                        //      { y: [a,b,c] ...} -> bindingPattern will have a property called propertyName for "y"
+                        // We have to explicitly emit the propertyName before descending into its binding elements.
+                        // Example:
+                        //      original: function foo({y: [a,b,c]}) {}
+                        //      emit    : declare function foo({y: [a, b, c]}: { y: [any, any, any] }) void;
+                        writeTextOfNode(currentSourceFile, bindingElement.propertyName);
+                        write(": ");
+
+                        // If bindingElement has propertyName property, then its name must be another bindingPattern of SyntaxKind.ObjectBindingPattern
+                        emitBindingPattern(<BindingPattern>bindingElement.name);
+                    }
+                    else if (bindingElement.name) {
+                        if (isBindingPattern(bindingElement.name)) {
+                            // If it is a nested binding pattern, we will recursively descend into each element and emit each one separately.
+                            // In the case of rest element, we will omit rest element.
+                            // Example:
+                            //      original: function foo([a, [[b]], c] = [1,[["string"]], 3]) {}
+                            //      emit    : declare function foo([a, [[b]], c]: [number, [[string]], number]): void;
+                            //      original with rest: function foo([a, ...c]) {}
+                            //      emit              : declare function foo([a, ...c]): void;
+                            emitBindingPattern(<BindingPattern>bindingElement.name);
+                        }
+                        else {
+                            Debug.assert(bindingElement.name.kind === SyntaxKind.Identifier);
+                            // If the node is just an identifier, we will simply emit the text associated with the node's name
+                            // Example:
+                            //      original: function foo({y = 10, x}) {}
+                            //      emit    : declare function foo({y, x}: {number, any}): void;
+                            if (bindingElement.dotDotDotToken) {
+                                write("...");
+                            }
+                            writeTextOfNode(currentSourceFile, bindingElement.name);
+                        }
+                    }
+                }
+            } 
         }
 
         function emitNode(node: Node) {

tests/baselines/reference/declarationEmitDestructuring1.js

@@ -0,0 +1,37 @@
+//// [declarationEmitDestructuring1.ts]
+function foo([a, b, c]: [string, string, string]): void { }
+function far([a, [b], [[c]]]: [number, boolean[], string[][]]): void { }
+function bar({a1, b1, c1}: { a1: number, b1: boolean, c1: string }): void { }
+function baz({a2, b2: {b1, c1}}: { a2: number, b2: { b1: boolean, c1: string } }): void { } 
+
+
+//// [declarationEmitDestructuring1.js]
+function foo(_a) {
+    var a = _a[0], b = _a[1], c = _a[2];
+}
+function far(_a) {
+    var a = _a[0], b = _a[1][0], c = _a[2][0][0];
+}
+function bar(_a) {
+    var a1 = _a.a1, b1 = _a.b1, c1 = _a.c1;
+}
+function baz(_a) {
+    var a2 = _a.a2, _b = _a.b2, b1 = _b.b1, c1 = _b.c1;
+}
+
+
+//// [declarationEmitDestructuring1.d.ts]
+declare function foo([a, b, c]: [string, string, string]): void;
+declare function far([a, [b], [[c]]]: [number, boolean[], string[][]]): void;
+declare function bar({a1, b1, c1}: {
+    a1: number;
+    b1: boolean;
+    c1: string;
+}): void;
+declare function baz({a2, b2: {b1, c1}}: {
+    a2: number;
+    b2: {
+        b1: boolean;
+        c1: string;
+    };
+}): void;

tests/baselines/reference/declarationEmitDestructuring1.types

@@ -0,0 +1,33 @@
+=== tests/cases/compiler/declarationEmitDestructuring1.ts ===
+function foo([a, b, c]: [string, string, string]): void { }
+>foo : ([a, b, c]: [string, string, string]) => void
+>a : string
+>b : string
+>c : string
+
+function far([a, [b], [[c]]]: [number, boolean[], string[][]]): void { }
+>far : ([a, [b], [[c]]]: [number, boolean[], string[][]]) => void
+>a : number
+>b : boolean
+>c : string
+
+function bar({a1, b1, c1}: { a1: number, b1: boolean, c1: string }): void { }
+>bar : ({a1, b1, c1}: { a1: number; b1: boolean; c1: string; }) => void
+>a1 : number
+>b1 : boolean
+>c1 : string
+>a1 : number
+>b1 : boolean
+>c1 : string
+
+function baz({a2, b2: {b1, c1}}: { a2: number, b2: { b1: boolean, c1: string } }): void { } 
+>baz : ({a2, b2: {b1, c1}}: { a2: number; b2: { b1: boolean; c1: string; }; }) => void
+>a2 : number
+>b2 : unknown
+>b1 : boolean
+>c1 : string
+>a2 : number
+>b2 : { b1: boolean; c1: string; }
+>b1 : boolean
+>c1 : string
+

tests/baselines/reference/declarationEmitDestructuring2.js

@@ -0,0 +1,43 @@
+//// [declarationEmitDestructuring2.ts]
+function f({x = 10, y: [a, b, c, d] = [1, 2, 3, 4]} = { x: 10, y: [2, 4, 6, 8] }) { }
+function g([a, b, c, d] = [1, 2, 3, 4]) { }
+function h([a, [b], [[c]], {x = 10, y: [a, b, c], z: {a1, b1}}]){ }
+function h1([a, [b], [[c]], {x = 10, y = [1, 2, 3], z: {a1, b1}}]){ }
+
+//// [declarationEmitDestructuring2.js]
+function f(_a) {
+    var _b = _a === void 0 ? { x: 10, y: [2, 4, 6, 8] } : _a, _c = _b.x, x = _c === void 0 ? 10 : _c, _d = _b.y, _e = _d === void 0 ? [1, 2, 3, 4] : _d, a = _e[0], b = _e[1], c = _e[2], d = _e[3];
+}
+function g(_a) {
+    var _b = _a === void 0 ? [1, 2, 3, 4] : _a, a = _b[0], b = _b[1], c = _b[2], d = _b[3];
+}
+function h(_a) {
+    var a = _a[0], b = _a[1][0], c = _a[2][0][0], _b = _a[3], _c = _b.x, x = _c === void 0 ? 10 : _c, _d = _b.y, a = _d[0], b = _d[1], c = _d[2], _e = _b.z, a1 = _e.a1, b1 = _e.b1;
+}
+function h1(_a) {
+    var a = _a[0], b = _a[1][0], c = _a[2][0][0], _b = _a[3], _c = _b.x, x = _c === void 0 ? 10 : _c, _d = _b.y, y = _d === void 0 ? [1, 2, 3] : _d, _e = _b.z, a1 = _e.a1, b1 = _e.b1;
+}
+
+
+//// [declarationEmitDestructuring2.d.ts]
+declare function f({x, y: [a, b, c, d]}?: {
+    x: number;
+    y: [number, number, number, number];
+}): void;
+declare function g([a, b, c, d]?: [number, number, number, number]): void;
+declare function h([a, [b], [[c]], {x, y: [a, b, c], z: {a1, b1}}]: [any, [any], [[any]], {
+    x?: number;
+    y: [any, any, any];
+    z: {
+        a1: any;
+        b1: any;
+    };
+}]): void;
+declare function h1([a, [b], [[c]], {x, y, z: {a1, b1}}]: [any, [any], [[any]], {
+    x?: number;
+    y?: number[];
+    z: {
+        a1: any;
+        b1: any;
+    };
+}]): void;

tests/baselines/reference/declarationEmitDestructuring2.types

@@ -0,0 +1,49 @@
+=== tests/cases/compiler/declarationEmitDestructuring2.ts ===
+function f({x = 10, y: [a, b, c, d] = [1, 2, 3, 4]} = { x: 10, y: [2, 4, 6, 8] }) { }
+>f : ({x = 10, y: [a, b, c, d] = [1, 2, 3, 4]}?: { x: number; y: [number, number, number, number]; }) => void
+>x : number
+>y : unknown
+>a : number
+>b : number
+>c : number
+>d : number
+>[1, 2, 3, 4] : [number, number, number, number]
+>{ x: 10, y: [2, 4, 6, 8] } : { x: number; y: [number, number, number, number]; }
+>x : number
+>y : [number, number, number, number]
+>[2, 4, 6, 8] : [number, number, number, number]
+
+function g([a, b, c, d] = [1, 2, 3, 4]) { }
+>g : ([a, b, c, d]?: [number, number, number, number]) => void
+>a : number
+>b : number
+>c : number
+>d : number
+>[1, 2, 3, 4] : [number, number, number, number]
+
+function h([a, [b], [[c]], {x = 10, y: [a, b, c], z: {a1, b1}}]){ }
+>h : ([a, [b], [[c]], {x = 10, y: [a, b, c], z: {a1, b1}}]: [any, [any], [[any]], { x?: number; y: [any, any, any]; z: { a1: any; b1: any; }; }]) => void
+>a : any
+>b : any
+>c : any
+>x : number
+>y : unknown
+>a : any
+>b : any
+>c : any
+>z : unknown
+>a1 : any
+>b1 : any
+
+function h1([a, [b], [[c]], {x = 10, y = [1, 2, 3], z: {a1, b1}}]){ }
+>h1 : ([a, [b], [[c]], {x = 10, y = [1, 2, 3], z: {a1, b1}}]: [any, [any], [[any]], { x?: number; y?: number[]; z: { a1: any; b1: any; }; }]) => void
+>a : any
+>b : any
+>c : any
+>x : number
+>y : number[]
+>[1, 2, 3] : number[]
+>z : unknown
+>a1 : any
+>b1 : any
+

tests/baselines/reference/declarationEmitDestructuring3.js

@@ -0,0 +1,18 @@
+//// [declarationEmitDestructuring3.ts]
+function bar([x, z, ...w]) { }
+function foo([x, ...y] = [1, "string", true]) { }
+
+
+
+//// [declarationEmitDestructuring3.js]
+function bar(_a) {
+    var x = _a[0], z = _a[1], w = _a.slice(2);
+}
+function foo(_a) {
+    var _b = _a === void 0 ? [1, "string", true] : _a, x = _b[0], y = _b.slice(1);
+}
+
+
+//// [declarationEmitDestructuring3.d.ts]
+declare function bar([x, z, ...w]: any[]): void;
+declare function foo([x, ...y]?: (string | number | boolean)[]): void;