fix #5539: improve isDef
type definition
#5549
Merged
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What kind of change does this PR introduce? (check at least one)
improve flow type coverage to make
isDef
narrow nullable value to no-null value.Does this PR introduce a breaking change? (check one)
If yes, please describe the impact and migration path for existing applications:
The PR fulfills these requirements:
dev
branch for v2.x (or to a previous version branch), not themaster
branchfix #xxx[,#xxx]
, where "xxx" is the issue number)Other information:
Currently
isDef
cannot narrow nullable value, as tracked in facebook/flow#34. Howerver, we can use a special%checks
comment to instruct flow inline the function.To make this happen, we need first to type check
utl/index.js
. So some type definition changes are required. I have tried my best to keep changes constrained to type level. But still some changes influence runtime.