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36 lines
906 B
36 lines
906 B
/** |
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* Helper function for exhaustive checks of discriminated unions. |
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* https://basarat.gitbooks.io/typescript/docs/types/discriminated-unions.html |
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* |
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* @example |
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* |
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* type A = {type: 'a'}; |
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* type B = {type: 'b'}; |
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* type Union = A | B; |
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* |
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* function doSomething(arg: Union) { |
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* if (arg.type === 'a') { |
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* return something; |
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* } |
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* |
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* if (arg.type === 'b') { |
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* return somethingElse; |
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* } |
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* |
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* // TS will error if there are other types in the union |
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* // Will throw an Error when called at runtime. |
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* // Use `assertNever(arg, true)` instead to fail silently. |
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* return assertNever(arg); |
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* } |
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*/ |
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export function assertNever(value: never, noThrow?: boolean): never { |
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if (noThrow) { |
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return value |
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} |
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throw new Error( |
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`Unhandled discriminated union member: ${JSON.stringify(value)}`, |
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); |
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} |
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export default assertNever;
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