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We observed for one project a new type error from trying to compare a string with an array after an Array.isArray check. The generics involved make a minimal reproduction infeasible but the essence of the code is:
if(Array.isArray(foo)){If(foo!=="something")// raises a new error for some complex foo}
Exports are hoisted to the top of a module
Module exports seem to be hoisted to the top of modules now. No runtime impact observed.
My educated guess is that the observed change was caused by the work done in #57946 and #57549
Improved narrowing of Array.isArray result
I don't think type predicate inference could change this anyhow. That change focuses on inferring some functions as type predicates. Array.isArray was already a type predicate - it's declaration is defined in a lib file.
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Acknowledgement
Comment
We are in the process of evaluating the impact of TS 5.5 beta on Bloomberg code. Below are preliminary findings.
Overall this looks to be a low-impact release. The following changes were observed and seem to either be benign in nature or else improvements:
Array.isArray
resultStricter type-checking of partial objects
We observed one project with a new type error in 5.5-beta, seemingly due to an improvement in type-checking for partials.
A minimal reproduction is here.
Improved narrowing of
Array.isArray
resultWe observed for one project a new type error from trying to compare a string with an array after an Array.isArray check. The generics involved make a minimal reproduction infeasible but the essence of the code is:
Exports are hoisted to the top of a module
Module exports seem to be hoisted to the top of modules now. No runtime impact observed.
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