21 lines
No EOL
741 B
TypeScript
21 lines
No EOL
741 B
TypeScript
// subtype checks use the apparent type of the target type
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// S is a subtype of a type T, and T is a supertype of S, if one of the following is true, where S' denotes the apparent type (section 3.8.1) of S:
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class Base<U extends String> {
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x: U;
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}
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// is String (S) a subtype of U extends String (T)? Would only be true if we used the apparent type of U (T)
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class Derived<U> extends Base<string> { // error
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x: String;
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}
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class Base2 {
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x: String;
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static s: String;
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}
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// is U extends String (S) a subtype of String (T)? Apparent type of U is String so it succeeds
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class Derived2<U extends String> extends Base2 { // error because of the prototype's not matching, not because of the instance side
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x: U;
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} |