Spurious "referenced directly or indirectly in its own initializer" when combined with narrowing, asserts function, and loop

[jakebailey]

Bug Report

🔎 Search Terms

referenced directly or indirectly asserts

🕗 Version & Regression Information

• This is the behavior in every version I tried

⏯ Playground Link

Playground Link

💻 Code

declare const myRequire: ((p: string) => {} | undefined) | undefined;

declare function assertIsDefined<T>(value: T): asserts value is NonNullable<T>

function fn1() {
    if (!myRequire) {
        return;
    }

    for (const p of ["a", "b"]) {
        // Error?
        const result = myRequire("something");
        assertIsDefined(result);
    }
}

🙁 Actual behavior

result is claimed to be referenced directly or indirectly in its initializer.

Modifying the code in various ways makes the error go away.

🙂 Expected behavior

No error; there's no relationship between the initializer and the result.

[ahejlsberg]

Here's what happens:

• checkVariableLikeDeclaration call for result variable.
• getTypeOfSymbol for result variable.
• Type is inferred from initializer, so checkExpression for myRequire("something").
• getFlowTypeOfReference for myRequire.
• getTypeAtFlowLoopLabel for back edge of loop.
• getEffectsSignature for assertIsDefined(result) call.
• inferTypeArguments for that call.
• checkExpression for result argument.
• getTypeOfSymbol for result variable.
• Circularity!

We probably could be a bit smarter about realizing that none of the arguments in the assertIsDefined(result) call match the reference (myRequire) for which we are currently doing CFA.

[TomerAberbach]

I'm noticing an odd "referenced directly or indirectly in its own initializer" error in my code. Wondering if you can help confirm whether this is the same issue or a separate one?

Playground link