98 lines
3.8 KiB
TypeScript
98 lines
3.8 KiB
TypeScript
// @downlevelIteration: true
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// A parameter declaration may specify either an identifier or a binding pattern.
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// The identifiers specified in parameter declarations and binding patterns
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// in a parameter list must be unique within that parameter list.
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// If the declaration includes a type annotation, the parameter is of that type
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function a1([a, b, [[c]]]: [number, number, string[][]]) { }
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function a2(o: { x: number, a: number }) { }
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function a3({j, k, l: {m, n}, q: [a, b, c]}: { j: number, k: string, l: { m: boolean, n: number }, q: (number|string)[] }) { };
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function a4({x, a}: { x: number, a: number }) { }
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a1([1, 2, [["world"]]]);
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a1([1, 2, [["world"]], 3]);
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// If the declaration includes an initializer expression (which is permitted only
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// when the parameter list occurs in conjunction with a function body),
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// the parameter type is the widened form (section 3.11) of the type of the initializer expression.
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function b1(z = [undefined, null]) { };
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function b2(z = null, o = { x: 0, y: undefined }) { }
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function b3({z: {x, y: {j}}} = { z: { x: "hi", y: { j: 1 } } }) { }
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interface F1 {
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b5(z, y, [, a, b], {p, m: { q, r}});
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}
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function b6([a, z, y] = [undefined, null, undefined]) { }
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function b7([[a], b, [[c, d]]] = [[undefined], undefined, [[undefined, undefined]]]) { }
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b1([1, 2, 3]); // z is widen to the type any[]
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b2("string", { x: 200, y: "string" });
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b2("string", { x: 200, y: true });
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b6(["string", 1, 2]); // Shouldn't be an error
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b7([["string"], 1, [[true, false]]]); // Shouldn't be an error
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// If the declaration specifies a binding pattern, the parameter type is the implied type of that binding pattern (section 5.1.3)
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enum Foo { a }
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function c0({z: {x, y: {j}}}) { }
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function c1({z} = { z: 10 }) { }
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function c2({z = 10}) { }
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function c3({b}: { b: number|string} = { b: "hello" }) { }
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function c5([a, b, [[c]]]) { }
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function c6([a, b, [[c=1]]]) { }
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c0({z : { x: 1, y: { j: "world" } }}); // Implied type is { z: {x: any, y: {j: any}} }
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c0({z : { x: "string", y: { j: true } }}); // Implied type is { z: {x: any, y: {j: any}} }
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c1(); // Implied type is {z:number}?
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c1({ z: 1 }) // Implied type is {z:number}?
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c2({}); // Implied type is {z?: number}
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c2({z:1}); // Implied type is {z?: number}
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c3({ b: 1 }); // Implied type is { b: number|string }.
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c5([1, 2, [["string"]]]); // Implied type is is [any, any, [[any]]]
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c5([1, 2, [["string"]], false, true]); // Implied type is is [any, any, [[any]]]
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// A parameter can be marked optional by following its name or binding pattern with a question mark (?)
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// or by including an initializer.
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function d0(x?) { }
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function d0(x = 10) { }
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interface F2 {
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d3([a, b, c]?);
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d4({x, y, z}?);
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e0([a, b, c]);
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}
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class C2 implements F2 {
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constructor() { }
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d3() { }
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d4() { }
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e0([a, b, c]) { }
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}
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class C3 implements F2 {
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d3([a, b, c]) { }
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d4({x, y, z}) { }
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e0([a, b, c]) { }
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}
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function d5({x, y} = { x: 1, y: 2 }) { }
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d5(); // Parameter is optional as its declaration included an initializer
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// Destructuring parameter declarations do not permit type annotations on the individual binding patterns,
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// as such annotations would conflict with the already established meaning of colons in object literals.
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// Type annotations must instead be written on the top- level parameter declaration
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function e1({x: number}) { } // x has type any NOT number
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function e2({x}: { x: number }) { } // x is type number
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function e3({x}: { x?: number }) { } // x is an optional with type number
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function e4({x: [number,string,any] }) { } // x has type [any, any, any]
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function e5({x: [a, b, c]}: { x: [number, number, number] }) { } // x has type [any, any, any]
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