54 lines
No EOL
2.9 KiB
TypeScript
54 lines
No EOL
2.9 KiB
TypeScript
//When used as a contextual type, a union type U has those members that are present in any of
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// its constituent types, with types that are unions of the respective members in the constituent types.
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interface SomeType {
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(a: number): number;
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}
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interface SomeType2 {
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(a: number): string;
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}
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interface IWithNoStringIndexSignature {
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foo: string;
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}
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interface IWithNoNumberIndexSignature {
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0: string;
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}
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interface IWithStringIndexSignature1 {
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[a: string]: SomeType;
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}
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interface IWithStringIndexSignature2 {
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[a: string]: SomeType2;
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}
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interface IWithNumberIndexSignature1 {
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[a: number]: SomeType;
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}
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interface IWithNumberIndexSignature2 {
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[a: number]: SomeType2;
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}
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// When an object literal is contextually typed by a type that includes a string index signature,
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// the resulting type of the object literal includes a string index signature with the union type of
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// the types of the properties declared in the object literal, or the Undefined type if the object literal
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// is empty.Likewise, when an object literal is contextually typed by a type that includes a numeric index
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// signature, the resulting type of the object literal includes a numeric index signature with the union type
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// of the types of the numerically named properties(section 3.7.4) declared in the object literal,
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// or the Undefined type if the object literal declares no numerically named properties.
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// Let S be the set of types in U that has a string index signature.
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// If S is not empty, U has a string index signature of a union type of
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// the types of the string index signatures from each type in S.
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var x: IWithNoStringIndexSignature | IWithStringIndexSignature1 = { z: a => a }; // a should be number
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var x: IWithNoStringIndexSignature | IWithStringIndexSignature1 = { foo: a => a }; // a should be number (because of index signature of IWithStringIndexSignature1)
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var x: IWithNoStringIndexSignature | IWithStringIndexSignature1 = { foo: "hello" };
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var x2: IWithStringIndexSignature1 | IWithStringIndexSignature2 = { z: a => a.toString() }; // a should be number
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var x2: IWithStringIndexSignature1 | IWithStringIndexSignature2 = { z: a => a }; // a should be number
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// Let S be the set of types in U that has a numeric index signature.
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// If S is not empty, U has a numeric index signature of a union type of
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// the types of the numeric index signatures from each type in S.
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var x3: IWithNoNumberIndexSignature | IWithNumberIndexSignature1 = { 1: a => a }; // a should be number
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var x3: IWithNoNumberIndexSignature | IWithNumberIndexSignature1 = { 0: a => a }; // a should be number (because of index signature of IWithNumberIndexSignature1)
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var x3: IWithNoNumberIndexSignature | IWithNumberIndexSignature1 = { 0: "hello" };
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var x4: IWithNumberIndexSignature1 | IWithNumberIndexSignature2 = { 1: a => a.toString() }; // a should be number
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var x4: IWithNumberIndexSignature1 | IWithNumberIndexSignature2 = { 1: a => a }; // a should be number
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