Implicitly casting non-numbers with a PrefixUnaryExpression should fail typechecks

[cpojer]

🔎 Search Terms

prefixunaryexpression

🕗 Version & Regression Information

• This is the behavior in every version I tried

⏯ Playground Link

https://www.typescriptlang.org/play?#code/MYGwhgzhAEAa0G8BQ1rAPYDsIBcBOArsDungBQAOBARiAJbDR4CmYAJliAJ5oF4uYcAYXS4AXNEwEAttWZ4AlIgC+SFNCq0G0AhTZgczMhnGSZcxYnWoWOPpknMA7nDI4AFnQgA6YHwHCojjQANRoQQoA3OqqqkgY2MEmwQC8iMkSAKzK0fFYuNAAHtBpmM6umVFqhd66+oZkALTJVWptbTV1BkbJ0ABU0I0AjFFAA

💻 Code

class X {
  constructor(public readonly currentCost: number) {}

  public update(cost: number) {
    return new X(this.currentCost + cost);
  }
}

const cost = {cost: 5};

const x = new X(5);

x.update(-cost); // Should error

x.update(cost * -1); // Errors correctly

🙁 Actual behavior

I refactored some code from returning a number to returning an object. I expect TypeScript to point me to all the places where I needed to make adjustments and came across one where I had -cost where cost was changed from a number to an object. TypeScript was not giving me an error like it does when I use cost * -1.

🙂 Expected behavior

I would expect TypeScript to prevent implicit casts on non number types (or non-scalar types in case there are valid use cases of this for boolean/strings) if a PrefixUnaryExpression is used. There are some fun JavaScript things that can be done by using -[] or -{}, it is almost never what a developer intents.

Additional information about the issue

No response

[RyanCavanaugh]

Duplicate #20131

[typescript-bot]

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