31 lines
1.4 KiB
Plaintext
31 lines
1.4 KiB
Plaintext
tests/cases/conformance/types/typeRelationships/apparentType/apparentTypeSubtyping.ts(9,7): error TS2415: Class 'Derived<U>' incorrectly extends base class 'Base<string>'.
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Types of property 'x' are incompatible.
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Type 'String' is not assignable to type 'string'.
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==== tests/cases/conformance/types/typeRelationships/apparentType/apparentTypeSubtyping.ts (1 errors) ====
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// 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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~~~~~~~
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!!! error TS2415: Class 'Derived<U>' incorrectly extends base class 'Base<string>'.
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!!! error TS2415: Types of property 'x' are incompatible.
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!!! error TS2415: Type 'String' is not assignable to type 'string'.
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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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} |