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tests/cases/compiler/implementGenericWithMismatchedTypes.ts(8,5): error TS2416: Property 'foo' in type 'C<T>' is not assignable to the same property in base type 'IFoo<T>'.
Type '(x: string) => number' is not assignable to type '(x: T) => T'.
Types of parameters 'x' and 'x' are incompatible.
Type 'T' is not assignable to type 'string'.
tests/cases/compiler/implementGenericWithMismatchedTypes.ts(17,5): error TS2416: Property 'foo' in type 'C2<T>' is not assignable to the same property in base type 'IFoo2<T>'.
Type '<Tstring>(x: Tstring) => number' is not assignable to type '(x: T) => T'.
Type 'number' is not assignable to type 'T'.
'T' could be instantiated with an arbitrary type which could be unrelated to 'number'.
==== tests/cases/compiler/implementGenericWithMismatchedTypes.ts (2 errors) ====
// no errors because in the derived types the best common type for T's value is Object
// and that matches the original signature for assignability since we treat its T's as Object
interface IFoo<T> {
foo(x: T): T;
}
class C<T> implements IFoo<T> { // error
foo(x: string): number {
~~~
!!! error TS2416: Property 'foo' in type 'C<T>' is not assignable to the same property in base type 'IFoo<T>'.
!!! error TS2416: Type '(x: string) => number' is not assignable to type '(x: T) => T'.
!!! error TS2416: Types of parameters 'x' and 'x' are incompatible.
!!! error TS2416: Type 'T' is not assignable to type 'string'.
!!! related TS2208 tests/cases/compiler/implementGenericWithMismatchedTypes.ts:7:9: This type parameter might need an `extends string` constraint.
return null;
}
}
interface IFoo2<T> {
foo(x: T): T;
}
class C2<T> implements IFoo2<T> { // error
foo<Tstring>(x: Tstring): number {
~~~
!!! error TS2416: Property 'foo' in type 'C2<T>' is not assignable to the same property in base type 'IFoo2<T>'.
!!! error TS2416: Type '<Tstring>(x: Tstring) => number' is not assignable to type '(x: T) => T'.
!!! error TS2416: Type 'number' is not assignable to type 'T'.
!!! error TS2416: 'T' could be instantiated with an arbitrary type which could be unrelated to 'number'.
return null;
}
}
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