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The explicit type is optional. It's not that it's required to copy out whatever the compiler inferred, it's just that lots of people do it to be explicit.

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All types are optional in typescript. I was just curious about Google's approach to it and if they had some standard practice of always copying the inferred type to get a great amount of coverage.

Copying the inferred type is the same as copying your runtime outputs into your tests. It's a statement that you believe the result is correct and it's on you to make that judgement call. It's not a policy to blindly copy everything, because that defeats the purpose of type checking and testing, turning your tests into " verify that nothing changed", not "verify that the system behaves as intended".

Thanks, thats typically how I approach it as well, it's good to hear it written out. I try not to append copied types without fully understanding their structure either. But sometimes you just need to just trust it to solve a problem.

There's plenty of blog posts and docs on advanced types but I'm interested in the day-to-day best practical approaches people are taking adopting it. I should look around for some literature or talks on the subject...

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