Intersection Types/function (something like `assert`): TS7030 TS2345

[zaoqi]

TypeScript Version: 3.3.3333

Search Terms:

Code

    const assert: ((x: false) => nerver) & ((x: true) => void) = (x: boolean) => {
        if (x === false) {
            return error()
        }
    }

Expected behavior:

Actual behavior:

lang.ts:1257:66 - error TS7030: Not all code paths return a value.

1257     const assert: ((x: false) => nerver) & ((x: true) => void) = (x: boolean) => {

lang.ts:1345:20 - error TS2345: Argument of type 'boolean' is not assignable to parameter of type 'true'.

1345             assert(!eof())

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Related Issues:

[yortus]

This CFA-based approach to handling assert functions is covered in #8655. E.g. see #8655 (comment).

That was closed as a design limitation. There is some reasoning and a future possible solution described in #8655 (comment)

[typescript-bot]

This issue has been marked as a 'Duplicate' and has seen no recent activity. It has been automatically closed for house-keeping purposes.