Improved checking of destructuring with literal initializers

src/compiler/diagnosticInformationMap.generated.ts

@@ -415,6 +415,7 @@ namespace ts {
         The_arguments_object_cannot_be_referenced_in_an_async_arrow_function_Consider_using_a_standard_async_function_expression: { code: 2522, category: DiagnosticCategory.Error, key: "The 'arguments' object cannot be referenced in an async arrow function. Consider using a standard async function expression." },
         yield_expressions_cannot_be_used_in_a_parameter_initializer: { code: 2523, category: DiagnosticCategory.Error, key: "'yield' expressions cannot be used in a parameter initializer." },
         await_expressions_cannot_be_used_in_a_parameter_initializer: { code: 2524, category: DiagnosticCategory.Error, key: "'await' expressions cannot be used in a parameter initializer." },
+        Initializer_provides_no_value_for_this_binding_element_and_the_binding_element_has_no_default_value: { code: 2525, category: DiagnosticCategory.Error, key: "Initializer provides no value for this binding element and the binding element has no default value." },
         JSX_element_attributes_type_0_must_be_an_object_type: { code: 2600, category: DiagnosticCategory.Error, key: "JSX element attributes type '{0}' must be an object type." },
         The_return_type_of_a_JSX_element_constructor_must_return_an_object_type: { code: 2601, category: DiagnosticCategory.Error, key: "The return type of a JSX element constructor must return an object type." },
         JSX_element_implicitly_has_type_any_because_the_global_type_JSX_Element_does_not_exist: { code: 2602, category: DiagnosticCategory.Error, key: "JSX element implicitly has type 'any' because the global type 'JSX.Element' does not exist." },

src/compiler/diagnosticMessages.json

@@ -1649,6 +1649,10 @@
         "category": "Error",
         "code": 2524
     },
+    "Initializer provides no value for this binding element and the binding element has no default value.": {
+        "category": "Error",
+        "code": 2525
+    },
     "JSX element attributes type '{0}' must be an object type.": {
         "category": "Error",
         "code": 2600

src/compiler/types.ts

@@ -1714,6 +1714,7 @@ namespace ts {
         resolvedExports?: SymbolTable;      // Resolved exports of module
         exportsChecked?: boolean;           // True if exports of external module have been checked
         isNestedRedeclaration?: boolean;    // True if symbol is block scoped redeclaration
+        bindingElement?: BindingElement;    // Binding element associated with property symbol
     }
 
     /* @internal */
@@ -1811,11 +1812,14 @@ namespace ts {
         PropagatingFlags = ContainsUndefinedOrNull | ContainsObjectLiteral | ContainsAnyFunctionType
     }
 
+    export type DestructuringPattern = BindingPattern | ObjectLiteralExpression | ArrayLiteralExpression;
+
     // Properties common to all types
     export interface Type {
-        flags: TypeFlags;               // Flags
-        /* @internal */ id: number;     // Unique ID
-        symbol?: Symbol;                // Symbol associated with type (if any)
+        flags: TypeFlags;                // Flags
+        /* @internal */ id: number;      // Unique ID
+        symbol?: Symbol;                 // Symbol associated with type (if any)
+        pattern?: DestructuringPattern;  // Destructuring pattern represented by type (if any)
     }
 
     /* @internal */
@@ -1864,8 +1868,7 @@ namespace ts {
     }
 
     export interface TupleType extends ObjectType {
-        elementTypes: Type[];          // Element types
-        baseArrayType: TypeReference;  // Array<T> where T is best common type of element types
+        elementTypes: Type[];           // Element types
     }
 
     export interface UnionOrIntersectionType extends Type {

tests/baselines/reference/arrowFunctionExpressions.types

@@ -100,12 +100,12 @@ var p8 = ({ a = 1 }) => { };
 >1 : number
 
 var p9 = ({ a: { b = 1 } = { b: 1 } }) => { };
->p9 : ({ a: { b = 1 } = { b: 1 } }: { a?: { b: number; }; }) => void
->({ a: { b = 1 } = { b: 1 } }) => { } : ({ a: { b = 1 } = { b: 1 } }: { a?: { b: number; }; }) => void
+>p9 : ({ a: { b = 1 } = { b: 1 } }: { a?: { b?: number; }; }) => void
+>({ a: { b = 1 } = { b: 1 } }) => { } : ({ a: { b = 1 } = { b: 1 } }: { a?: { b?: number; }; }) => void
 >a : any
 >b : number
 >1 : number
->{ b: 1 } : { b: number; }
+>{ b: 1 } : { b?: number; }
 >b : number
 >1 : number
 

tests/baselines/reference/declarationEmitDestructuring2.js

@@ -21,8 +21,8 @@ function h1(_a) {
 
 //// [declarationEmitDestructuring2.d.ts]
 declare function f({x, y: [a, b, c, d]}?: {
-    x: number;
-    y: [number, number, number, number];
+    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]], {

tests/baselines/reference/declarationEmitDestructuring4.errors.txt

@@ -0,0 +1,17 @@
+tests/cases/compiler/declarationEmitDestructuring4.ts(9,22): error TS2353: Object literal may only specify known properties, and 'x' does not exist in type '{}'.
+
+
+==== tests/cases/compiler/declarationEmitDestructuring4.ts (1 errors) ====
+    // For an array binding pattern with empty elements,
+    // we will not make any modification and will emit
+    // the similar binding pattern users' have written
+    function baz([]) { }
+    function baz1([] = [1,2,3]) { }
+    function baz2([[]] = [[1,2,3]]) { }
+
+    function baz3({}) { }
+    function baz4({} = { x: 10 }) { }
+                         ~
+!!! error TS2353: Object literal may only specify known properties, and 'x' does not exist in type '{}'.
+
+

tests/baselines/reference/declarationEmitDestructuringArrayPattern2.errors.txt

@@ -0,0 +1,22 @@
+tests/cases/compiler/declarationEmitDestructuringArrayPattern2.ts(4,6): error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
+tests/cases/compiler/declarationEmitDestructuringArrayPattern2.ts(4,11): error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
+tests/cases/compiler/declarationEmitDestructuringArrayPattern2.ts(4,16): error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
+
+
+==== tests/cases/compiler/declarationEmitDestructuringArrayPattern2.ts (3 errors) ====
+    var [x10, [y10, [z10]]] = [1, ["hello", [true]]];
+
+    var [x11 = 0, y11 = ""] = [1, "hello"];
+    var [a11, b11, c11] = [];
+         ~~~
+!!! error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
+              ~~~
+!!! error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
+                   ~~~
+!!! error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
+
+    var [a2, [b2, { x12, y12: c2 }]=["abc", { x12: 10, y12: false }]] = [1, ["hello", { x12: 5, y12: true }]];
+
+    var [x13, y13] = [1, "hello"];
+    var [a3, b3] = [[x13, y13], { x: x13, y: y13 }];
+

tests/baselines/reference/declarationEmitDestructuringObjectLiteralPattern.errors.txt

@@ -0,0 +1,43 @@
+tests/cases/compiler/declarationEmitDestructuringObjectLiteralPattern.ts(2,13): error TS2353: Object literal may only specify known properties, and 'x' does not exist in type '{}'.
+tests/cases/compiler/declarationEmitDestructuringObjectLiteralPattern.ts(2,19): error TS2353: Object literal may only specify known properties, and 'y' does not exist in type '{}'.
+tests/cases/compiler/declarationEmitDestructuringObjectLiteralPattern.ts(3,23): error TS2353: Object literal may only specify known properties, and 'y4' does not exist in type '{ x4: any; }'.
+tests/cases/compiler/declarationEmitDestructuringObjectLiteralPattern.ts(4,16): error TS2353: Object literal may only specify known properties, and 'x5' does not exist in type '{ y5: any; }'.
+tests/cases/compiler/declarationEmitDestructuringObjectLiteralPattern.ts(6,27): error TS2353: Object literal may only specify known properties, and 'y7' does not exist in type '{ x7: any; }'.
+tests/cases/compiler/declarationEmitDestructuringObjectLiteralPattern.ts(7,20): error TS2353: Object literal may only specify known properties, and 'x8' does not exist in type '{ y8: any; }'.
+
+
+==== tests/cases/compiler/declarationEmitDestructuringObjectLiteralPattern.ts (6 errors) ====
+
+    var { } = { x: 5, y: "hello" };
+                ~
+!!! error TS2353: Object literal may only specify known properties, and 'x' does not exist in type '{}'.
+                      ~
+!!! error TS2353: Object literal may only specify known properties, and 'y' does not exist in type '{}'.
+    var { x4 } = { x4: 5, y4: "hello" };
+                          ~~
+!!! error TS2353: Object literal may only specify known properties, and 'y4' does not exist in type '{ x4: any; }'.
+    var { y5 } = { x5: 5, y5: "hello" };
+                   ~~
+!!! error TS2353: Object literal may only specify known properties, and 'x5' does not exist in type '{ y5: any; }'.
+    var { x6, y6 } = { x6: 5, y6: "hello" };
+    var { x7: a1 } = { x7: 5, y7: "hello" };
+                              ~~
+!!! error TS2353: Object literal may only specify known properties, and 'y7' does not exist in type '{ x7: any; }'.
+    var { y8: b1 } = { x8: 5, y8: "hello" };
+                       ~~
+!!! error TS2353: Object literal may only specify known properties, and 'x8' does not exist in type '{ y8: any; }'.
+    var { x9: a2, y9: b2 } = { x9: 5, y9: "hello" };
+
+    var { a: x11, b: { a: y11, b: { a: z11 }}} = { a: 1, b: { a: "hello", b: { a: true } } };
+
+    function f15() {
+        var a4 = "hello";
+        var b4 = 1;
+        var c4 = true;
+        return { a4, b4, c4 };
+    }
+    var { a4, b4, c4 } = f15();
+
+    module m {
+        export var { a4, b4, c4 } = f15();
+    }