41 lines
1.5 KiB
JavaScript
41 lines
1.5 KiB
JavaScript
// @flow
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function apply<Args: $ReadOnlyArray<mixed>, Ret>(
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fn: (...Args) => Ret,
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args: Args,
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): Ret {
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return fn(...args);
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}
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function noRest(x: 'hi', y: 123): true { return true; }
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apply(noRest, ['hi', 123]); // No error
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apply(noRest, ['hi', 456]); // Error - 456 ~> 123
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apply(noRest, ['hi']); // Error - too few args
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apply(noRest, ['hi', 123, false]); // No error - too many args is fine
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// withRest behaves the same as noRest except you can't pass too many args in
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function withRest(...rest: ['hi', 123]): true { return true; }
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apply(withRest, ['hi', 123]); // No error
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apply(withRest, ['hi', 456]); // Error - 456 ~> 123
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apply(withRest, ['hi']); // Error - too few args
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apply(withRest, ['hi', 123, false]); // Error - too many args
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// Same thing, but with types instead of functions
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declare var applyType: <Args: $ReadOnlyArray<mixed>, Ret>(
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fn: (...Args) => Ret,
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args: Args,
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) => Ret;
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function noRest(x: 'hi', y: 123): true { return true; }
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applyType(noRest, ['hi', 123]); // No error
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applyType(noRest, ['hi', 456]); // Error - 456 ~> 123
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applyType(noRest, ['hi']); // Error - too few args
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applyType(noRest, ['hi', 123, false]); // No error - too many args is fine
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// withRest behaves the same as noRest except you can't pass too many args in
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function withRest(...rest: ['hi', 123]): true { return true; }
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applyType(withRest, ['hi', 123]); // No error
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applyType(withRest, ['hi', 456]); // Error - 456 ~> 123
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applyType(withRest, ['hi']); // Error - too few args
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applyType(withRest, ['hi', 123, false]); // Error - too many args
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