use [""] in object will lose ts check #58908

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1. RyanCavanaugh commented on Jun 18, 2024

   

   Ryan Cavanaugh (RyanCavanaugh)

   on Jun 18, 2024

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   I'm not sure what's best here. We show

   (property) a1: 1

   But a2 isn't a property; it's an index signature. It'd be confusing to just show

   number

   here since "a2" is not a number.

   We've never had reason to show (index signature) or whatnot here.

   This doesn't seem like something people commonly encounter as a problem.
2. Ryan Cavanaugh (RyanCavanaugh)

   added

   SuggestionAn idea for TypeScriptAn idea for TypeScript

   Awaiting More FeedbackThis means we'd like to hear from more people who would be helped by this featureThis means we'd like to hear from more people who would be helped by this feature

   Domain: LS: Quick Infoe.g. hover text, tool-tips, and tooltips.e.g. hover text, tool-tips, and tooltips.

   on Jun 18, 2024
3. fatcerberus commented on Jun 18, 2024

   

   Bruce Pascoe (fatcerberus)

   on Jun 18, 2024

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   Note that this isn't just about twoslash hints, but extends to hover tips as well. It is kind of frustratingly inconsistent (for no apparent reason, from an end-user point of view) that hovering over ["a1"] shows what type of value it's accessing, but not ["a2"]. If you want to see that type you have to assign it to a const first and hover over that.
4. DanielRosenwasser commented on Jun 18, 2024

   

   Daniel Rosenwasser (DanielRosenwasser)

   on Jun 18, 2024

   Last edited by DanielRosenwasser

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   How about number from [x: string]: number? Works similarly to how we show type parameters as T in f<T>(): void.
5. Kanade-Lu commented on Jun 19, 2024

   

   Kanade-Lu (Kanade-Lu)

   on Jun 19, 2024

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   How about number from [x: string]: number? Works similarly to how we show type parameters as T in f<T>(): void.怎么样 number from [x: string]: number ？工作方式类似于我们将类型参数显示为 T in f<T>(): void .

   This seems intuitive.
   While I'm not sure what's best to show, I'm a little confused that typescript shows me nothing when I encounter this situation.
6. kermanx commented on Jun 19, 2024

   

   _Kerman (kermanx)

   on Jun 19, 2024

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   More information: If you destruct the object, then the type will be shown:

   

   Playground
7. Andarist commented on Aug 20, 2024

   

   Mateusz Burzyński (Andarist)

   on Aug 20, 2024

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   How about number from [x: string]: number? Works similarly to how we show type parameters as T in f(): void.

   There is already some support for those kinds of displays and the format is different (TS playground):

   interface Foo {
     x: string
     [k: string]: string | number;
   }
   
   declare const foo: Foo
   
   foo.something
   //   ^? (index) Foo[string]: string | number

   The formatting issue here is, in part, related to the fact that this index signature comes from a mapped type (TS playground):

   type Foo = Record<string, string | number>;
   
   declare const foo: Foo;
   
   foo.something;
   //   ^? string | number

   and in part that it comes from an intersection since this doesn't work either (TS playground):

   interface Bar {
     [k: string]: string | number;
   }
   
   interface Foo {
     x: string;
   }
   
   declare const foo: Foo & Bar;
   
   foo.something;
   //   ^? string | number

   None of those works with foo['something'].