Comparison targets are reversed (regression) #30118

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1. Ryan Cavanaugh (RyanCavanaugh)

   added

   Needs More InfoThe issue still hasn't been fully clarifiedThe issue still hasn't been fully clarified

   on Feb 27, 2019
2. RyanCavanaugh commented on Feb 27, 2019

   

   Ryan Cavanaugh (RyanCavanaugh)

   on Feb 27, 2019

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   falsandtru (@falsandtru) please provide a reduced repro - thanks!
3. jack-williams commented on Feb 27, 2019

   

   Jack Williams (jack-williams)

   on Feb 27, 2019

   Last edited by jack-williams

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   falsandtru (@falsandtru) Is this a repro?

   interface Foo<T> {
       cast(name: ('' extends T ? string : string)): void;
   }
   
   interface Foo2<T> {
       cast(name: ('' extends T ? string : string)): void;
   }
   
   declare const y: Foo<string>;
   const x: Foo<''> = y; // error
   
   declare const y2: Foo2<string>;
   const x2: Foo<''> = y2; // ok
4. falsandtru commented on Feb 27, 2019

   

   falsandtru (falsandtru)

   on Feb 27, 2019

   Last edited by falsandtru

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   Ryan Cavanaugh (@RyanCavanaugh) Repro

   export abstract class Supervisor<N extends string, P = unknown, R = unknown> {
     private static instances_: Set<Supervisor<string, unknown, unknown>>;
     private static get instances(): typeof Supervisor.instances_ {
       return this.hasOwnProperty('instances_')
         ? this.instances_
         : this.instances_ = new Set();
     }
     constructor() {
       void (this.constructor as typeof Supervisor).instances.add(this);
     }
     public abstract call(name: N | ('' extends N ? undefined : never), param: P, timeout?: number): Promise<R>;
   }

   Jack Williams (@jack-williams) No. The type parameters in your repro are not reversed.
5. jack-williams commented on Feb 27, 2019

   

   Jack Williams (jack-williams)

   on Feb 27, 2019

   Last edited by jack-williams

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   falsandtru (@falsandtru) Yep, sorry. What about this?

   class Foo<T extends string> {
       private static instance: Foo<string>[];
   
       cast(_name: ([T] extends [string] ? string : string)) {
           
       }
       
       foobar() {
           Foo.instance.push(this);
       }
   }
6. falsandtru commented on Feb 27, 2019

   

   falsandtru (falsandtru)

   on Feb 27, 2019

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   Looks like good except an illegal ! at the second line.

   👍React with 👍1Reacted by Jack Williams
7. Ryan Cavanaugh (RyanCavanaugh)

   removed

   Needs More InfoThe issue still hasn't been fully clarifiedThe issue still hasn't been fully clarified

   on Feb 28, 2019
8. Ryan Cavanaugh (RyanCavanaugh)

   assigned

   Wesley Wigham (weswigham)

   on Feb 28, 2019
9. Ryan Cavanaugh (RyanCavanaugh)

   added

   Needs InvestigationThis issue needs a team member to investigate its status.This issue needs a team member to investigate its status.

   on Feb 28, 2019
10. Ryan Cavanaugh (RyanCavanaugh)

    closed this as not plannedon Oct 22, 2025