26 lines
1.1 KiB
Plaintext
26 lines
1.1 KiB
Plaintext
==== tests/cases/conformance/types/typeRelationships/apparentType/apparentTypeSubtyping.ts (1 errors) ====
|
|
// subtype checks use the apparent type of the target type
|
|
// 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:
|
|
|
|
class Base<U extends String> {
|
|
x: U;
|
|
}
|
|
|
|
// is String (S) a subtype of U extends String (T)? Would only be true if we used the apparent type of U (T)
|
|
class Derived<U> extends Base<string> { // error
|
|
~~~~~~~
|
|
!!! Class 'Derived<U>' incorrectly extends base class 'Base<string>':
|
|
!!! Types of property 'x' are incompatible:
|
|
!!! Type 'String' is not assignable to type 'string'.
|
|
x: String;
|
|
}
|
|
|
|
class Base2 {
|
|
x: String;
|
|
static s: String;
|
|
}
|
|
|
|
// is U extends String (S) a subtype of String (T)? Apparent type of U is String so it succeeds
|
|
class Derived2<U extends String> extends Base2 { // error because of the prototype's not matching, not because of the instance side
|
|
x: U;
|
|
} |