A few days ago I shared a small CLI experiment called fixmyfile that automatically fixes repetitive TypeScript errors using compiler diagnostics and AST transformations.

While testing it more, I kept running into another frustrating TypeScript pattern:

const users = data . filter ( Boolean );

users . map (( u ) => u . name );

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Even after filtering values, TypeScript can still complain that:

'u' is possibly undefined

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Logically the values are already filtered, but TypeScript narrowing does not always behave the way developers expect.

So I started experimenting with AST-based transformations for these cases too.

Now the CLI automatically converts:

const users = data . filter ( Boolean );

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into:

const users = data .…