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Array.length type guard for array spreading #28837

@MidnightDesign

Description

@MidnightDesign

TypeScript Version: 3.3.0-dev.20181204

Search Terms: array length type guard spread

Code

const timeString = '09:00';
const date = new Date();
const timeParts = timeString.split(':').map((part) => parseInt(part, 10));
if (timeParts.length > 0) {
    date.setHours(...timeParts);
}

Expected behavior: No errors

Actual behavior: TS2556: Expected 1-4 arguments, but got 0 or more.

Playground Link: https://www.typescriptlang.org/play/#src=const%20timeString%20%3D%20'09%3A00'%3B%0D%0Aconst%20date%20%3D%20new%20Date()%3B%0D%0Aconst%20timeParts%20%3D%20timeString.split('%3A').map((part)%20%3D%3E%20parseInt(part%2C%2010))%3B%0D%0Aif%20(timeParts.length%20%3E%200)%20%7B%0D%0A%20%20%20%20date.setHours(...timeParts)%3B%0D%0A%7D%0D%0A

Related Issues: None

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