Regression in detecting unused parameters in 5.5.0-beta

[danvk]

🔎 Search Terms

• 5.5 predicate
• 6133

🕗 Version & Regression Information

• This changed between versions 5.4.5 and 5.5.0-beta

⏯ Playground Link

https://www.typescriptlang.org/play/?ts=5.5.0-beta#code/GYVwdgxgLglg9mABABwE4FMAmB1GUAWAqmCAM5YAUAhgFyLgDWYcA7mAJSIDeAUIv4gxQQqJAEIxAWSoEAdKiphMcALYV2Abh4BfHkA

💻 Code

function predWithUnused(a: unknown) {
    return !!Math.random();
}

🙁 Actual behavior

TS 5.5.0-beta reports that a is used.

🙂 Expected behavior

It should be reported as unused.

Additional information about the issue

Compare 5.4.5

vs. 5.5.0-beta:

This was almost certainly broken by #57465. It adds a call to getTypeOfSymbol for every parameter of a candidate predicate function in checkIfExpressionRefinesAnyParameter. This marks each of those parameters as referenced, even though there's no reason to assume that they are, since this call is speculative.

This also affects the "Delete all unused declarations" quickfix.