19 lines
372 B
TypeScript
19 lines
372 B
TypeScript
class Chain<T extends A> {
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constructor(public value: T) { }
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then<S extends T>(cb: (x: T) => S): Chain<S> {
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return null;
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}
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}
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class A {
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x;
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}
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class B extends A {
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y;
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}
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class C extends B {
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z;
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}
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// Ok to go down the chain, but error to try to climb back up
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(new Chain(new A)).then(a => new B).then(b => new C).then(c => new B).then(b => new A); |