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=== tests/cases/compiler/assertionFunctionsCanNarrowByDiscriminant.ts ===
interface Cat {
type: 'cat';
>type : "cat"
canMeow: true;
>canMeow : true
>true : true
}
interface Dog {
type: 'dog';
>type : "dog"
canBark: true;
>canBark : true
>true : true
}
type Animal = Cat | Dog;
>Animal : Cat | Dog
declare function assertEqual<T>(value: any, type: T): asserts value is T;
>assertEqual : <T>(value: any, type: T) => asserts value is T
>value : any
>type : T
const animal = { type: 'cat', canMeow: true } as Animal;
>animal : Animal
>{ type: 'cat', canMeow: true } as Animal : Animal
>{ type: 'cat', canMeow: true } : { type: "cat"; canMeow: true; }
>type : "cat"
>'cat' : "cat"
>canMeow : true
>true : true
assertEqual(animal.type, 'cat' as const);
>assertEqual(animal.type, 'cat' as const) : void
>assertEqual : <T>(value: any, type: T) => asserts value is T
>animal.type : "cat" | "dog"
>animal : Animal
>type : "cat" | "dog"
>'cat' as const : "cat"
>'cat' : "cat"
animal.canMeow; // since is cat, should not be an error
>animal.canMeow : true
>animal : Cat
>canMeow : true
const animalOrUndef = { type: 'cat', canMeow: true } as Animal | undefined;
>animalOrUndef : Animal | undefined
>{ type: 'cat', canMeow: true } as Animal | undefined : Animal | undefined
>{ type: 'cat', canMeow: true } : { type: "cat"; canMeow: true; }
>type : "cat"
>'cat' : "cat"
>canMeow : true
>true : true
assertEqual(animalOrUndef?.type, 'cat' as const);
>assertEqual(animalOrUndef?.type, 'cat' as const) : void
>assertEqual : <T>(value: any, type: T) => asserts value is T
>animalOrUndef?.type : "cat" | "dog" | undefined
>animalOrUndef : Animal | undefined
>type : "cat" | "dog" | undefined
>'cat' as const : "cat"
>'cat' : "cat"
animalOrUndef.canMeow; // since is cat, should not be an error
>animalOrUndef.canMeow : true
>animalOrUndef : Cat
>canMeow : true
|
