In-line callbacks in for..of loops have access to the iteration variable #2693

R-unic · 2024-05-17T20:29:10Z

public setColor(color: Color3): void {
    for (const child of this.instance.GetChildren().filter((i): i is Frame => child.IsA("Frame")))
      child.BackgroundColor3 = color;
  }

In this instance an error should be thrown because the object being iterated is referencing the iteration variable in the callback for filter. This compiles with no error on roblox-ts@2.3.0.

This example also comes from me refactoring and forgetting to change child to i, and it went unnoticed until it errored in game.

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Dionysusnu · 2024-05-17T21:59:28Z

Roblox-ts doesn't have control over type or scope checking behaviour, we leave it up to Typescript. You can see in this playground example how it allows similar unintuitive behaviour, which errors in JS as well.

R-unic · 2024-05-17T22:01:56Z

very bizarre. you'd think there'd be some way to circumvent this when compiling though

Dionysusnu · 2024-05-17T22:07:17Z

I haven't been able to find any cases where this doesn't error in JS, so I wonder if this would count as a reasonably-fixable-bug on the TypeScript side. You could try making an issue there.

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In-line callbacks in for..of loops have access to the iteration variable #2693

In-line callbacks in for..of loops have access to the iteration variable #2693

In-line callbacks in for..of loops have access to the iteration variable #2693

In-line callbacks in for..of loops have access to the iteration variable #2693

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