Emit destructuring in parameter

Author: Yui T

src/compiler/declarationEmitter.ts

@@ -1291,7 +1291,8 @@ module ts {
                 write("...");
             }
             if (isBindingPattern(node.name)) {
-                write("_" + indexOf((<FunctionLikeDeclaration>node.parent).parameters, node));
+                // By emitting binding pattern as binding pattern in function parameters, language service can provide better signature help
+                write(getTextOfNode(node.name));
             }
             else {
                 writeTextOfNode(currentSourceFile, node.name);

tests/baselines/reference/declarationEmitDestructuringArrayPattern5.js

@@ -0,0 +1,37 @@
+//// [declarationEmitDestructuringArrayPattern5.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 { } 
+
+
+//// [declarationEmitDestructuringArrayPattern5.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;
+}
+
+
+//// [declarationEmitDestructuringArrayPattern5.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/declarationEmitDestructuringArrayPattern5.types

@@ -0,0 +1,33 @@
+=== tests/cases/compiler/declarationEmitDestructuringArrayPattern5.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/declarationEmitDestructuringOptionalBindingParametersInOverloads.js

@@ -25,8 +25,8 @@ function foo2() {
 
 
 //// [declarationEmitDestructuringOptionalBindingParametersInOverloads.d.ts]
-declare function foo(_0?: [string, number, boolean]): any;
-declare function foo2(_0?: {
+declare function foo([x, y, z]?: [string, number, boolean]): any;
+declare function foo2({ x, y, z }?: {
     x: string;
     y: number;
     z: boolean;

tests/baselines/reference/declarationEmitDestructuringParameterProperties.js

@@ -43,12 +43,12 @@ var C3 = (function () {
 //// [declarationEmitDestructuringParameterProperties.d.ts]
 declare class C1 {
     x: string, y: string, z: string;
-    constructor(_0: string[]);
+    constructor([x, y, z]: string[]);
 }
 declare type TupleType1 = [string, number, boolean];
 declare class C2 {
     x: string, y: number, z: boolean;
-    constructor(_0: TupleType1);
+    constructor([x, y, z]: TupleType1);
 }
 declare type ObjType1 = {
     x: number;
@@ -57,5 +57,5 @@ declare type ObjType1 = {
 };
 declare class C3 {
     x: number, y: string, z: boolean;
-    constructor(_0: ObjType1);
+    constructor({ x, y, z }: ObjType1);
 }

tests/baselines/reference/declarationEmitDestructuringWithOptionalBindingParameters.js

@@ -14,8 +14,8 @@ function foo1(_a) {
 
 
 //// [declarationEmitDestructuringWithOptionalBindingParameters.d.ts]
-declare function foo(_0?: [string, number, boolean]): void;
-declare function foo1(_0?: {
+declare function foo([x,y,z]?: [string, number, boolean]): void;
+declare function foo1({ x, y, z }?: {
     x: string;
     y: number;
     z: boolean;

tests/cases/compiler/declarationEmitDestructuringArrayPattern5.ts

@@ -0,0 +1,5 @@
+// @declaration: true
+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 { }