27 lines
976 B
Plaintext
27 lines
976 B
Plaintext
==== tests/cases/conformance/classes/members/inheritanceAndOverriding/derivedClassTransitivity3.ts (1 errors) ====
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// subclassing is not transitive when you can remove required parameters and add optional parameters
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class C<T> {
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foo(x: T, y: T) { }
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}
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class D<T> extends C<T> {
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foo(x: T) { } // ok to drop parameters
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}
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class E<T> extends D<T> {
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foo(x: T, y?: number) { } // ok to add optional parameters
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}
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var c: C<string>;
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var d: D<string>;
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var e: E<string>;
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c = e;
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~
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!!! Type 'E<string>' is not assignable to type 'C<string>':
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!!! Types of property 'foo' are incompatible:
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!!! Type '(x: string, y?: number) => void' is not assignable to type '(x: string, y: string) => void':
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!!! Types of parameters 'y' and 'y' are incompatible:
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!!! Type 'number' is not assignable to type 'string'.
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var r = c.foo('', '');
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var r2 = e.foo('', 1); |