76 lines
2.1 KiB
TypeScript
76 lines
2.1 KiB
TypeScript
class C { private p: string };
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var str: string;
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var bool: boolean;
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var num: number;
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var strOrNum: string | number;
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var strOrBool: string | boolean;
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var numOrBool: number | boolean
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var strOrNumOrBool: string | number | boolean;
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var strOrC: string | C;
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var numOrC: number | C;
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var boolOrC: boolean | C;
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var emptyObj: {};
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var c: C;
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// A type guard of the form typeof x === s,
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// where s is a string literal with any value but 'string', 'number' or 'boolean',
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// - when true, removes the primitive types string, number, and boolean from the type of x, or
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// - when false, has no effect on the type of x.
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if (typeof strOrC === "Object") {
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c = strOrC; // C
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}
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else {
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var r2: string | C = strOrC; // string | C
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}
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if (typeof numOrC === "Object") {
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c = numOrC; // C
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}
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else {
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var r3: number | C = numOrC; // number | C
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}
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if (typeof boolOrC === "Object") {
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c = boolOrC; // C
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}
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else {
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var r4: boolean | C = boolOrC; // boolean | C
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}
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// Narrowing occurs only if target type is a subtype of variable type
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if (typeof strOrNumOrBool === "Object") {
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var q1: string | number | boolean = strOrNumOrBool; // string | number | boolean
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}
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else {
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var q2: string | number | boolean = strOrNumOrBool; // string | number | boolean
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}
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// A type guard of the form typeof x !== s, where s is a string literal,
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// - when true, narrows the type of x by typeof x === s when false, or
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// - when false, narrows the type of x by typeof x === s when true.
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if (typeof strOrC !== "Object") {
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var r2: string | C = strOrC; // string | C
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}
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else {
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c = strOrC; // C
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}
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if (typeof numOrC !== "Object") {
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var r3: number | C = numOrC; // number | C
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}
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else {
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c = numOrC; // C
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}
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if (typeof boolOrC !== "Object") {
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var r4: boolean | C = boolOrC; // boolean | C
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}
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else {
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c = boolOrC; // C
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}
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// Narrowing occurs only if target type is a subtype of variable type
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if (typeof strOrNumOrBool !== "Object") {
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var q1: string | number | boolean = strOrNumOrBool; // string | number | boolean
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}
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else {
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var q2: string | number | boolean = strOrNumOrBool; // string | number | boolean
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}
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