generics can only detect arrow function in object but not function expression #57572

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1. Andarist commented on Feb 28, 2024

   

   Mateusz Burzyński (Andarist)

   on Feb 28, 2024

   Contributor

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   An object method without an explicit this parameter is going to always be context-sensitive (it has that implied this parameter). Your issue falls under this umbrella issue: #47599

   You can verify this by annotating this explicitly in your bbb:

   type C = <Methods, Attached extends (methods: Methods) => void>(options: {
     methods: Methods;
     attached: Attached;
   }) => any;
   
   var Component: C = () => {};
   
   Component({
     attached(methods) {
       methods.bbb(); // ok
     },
     methods: {
       bbb(this: unknown) {},
     },
   });
2. Asweallcan commented on Feb 28, 2024

   

   lvshihao (Asweallcan)

   on Feb 28, 2024

   Author

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   An object method without an explicit this parameter is going to always be context-sensitive (it has that implied this parameter). Your issue falls under this umbrella issue: #47599

   You can verify this by annotating this explicitly in your bbb:

   type C = <Methods, Attached extends (methods: Methods) => void>(options: {
     methods: Methods;
     attached: Attached;
   }) => any;
   
   var Component: C = () => {};
   
   Component({
     attached(methods) {
       methods.bbb(); // ok
     },
     methods: {
       bbb(this: unknown) {},
     },
   });

   what if I need to use Type C to define bbb's "this" type，will this issue be solved or not? Mateusz Burzyński (@Andarist)
3. Andarist commented on Feb 28, 2024

   

   Mateusz Burzyński (Andarist)

   on Feb 28, 2024

   Contributor

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   You can even workaround this particular situation by reordering your attached and methods. attached acts as a consumer here and it's better to put the consumer after the producer (methods here):

   type C = <Methods, Attached extends (methods: Methods) => void>(options: {
     methods: Methods;
     attached: Attached;
   }) => any;
   
   var Component: C = () => {};
   
   Component({
     methods: {
       bbb() {}, // no `this` annotation!
     },
     attached(methods) {
       methods.bbb(); // ok, yay!
     },
   });
4. Asweallcan commented on Feb 28, 2024

   

   lvshihao (Asweallcan)

   on Feb 28, 2024

   Author

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   You can even workaround this particular situation by reordering your attached and methods. attached acts as a consumer here and it's better to put the consumer after the producer (methods here):

   type C = <Methods, Attached extends (methods: Methods) => void>(options: {
     methods: Methods;
     attached: Attached;
   }) => any;
   
   var Component: C = () => {};
   
   Component({
     methods: {
       bbb() {}, // no `this` annotation!
     },
     attached(methods) {
       methods.bbb(); // ok, yay!
     },
   });

   ohhhhhhhh, I will try this, thanks
5. Ryan Cavanaugh (RyanCavanaugh)

   added

   DuplicateAn existing issue was already createdAn existing issue was already created

   on Feb 28, 2024
6. typescript-bot commented on Mar 2, 2024

   

   TypeScript Bot (typescript-bot)

   on Mar 2, 2024

   Contributor

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   This issue has been marked as "Duplicate" and has seen no recent activity. It has been automatically closed for house-keeping purposes.
7. TypeScript Bot (typescript-bot)

   closed this as not plannedon Mar 2, 2024
8. microsoft

   locked as resolved and limited conversation to collaborators on Oct 22, 2025
9. Gabriela Araujo Britto (gabritto)

   closed this as completedin #62243on Dec 10, 2025