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Type inference regression (regression) #37383

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Type inference regression (regression)#37383
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BugA bug in TypeScriptDomain: check: Type InferenceRelated to type inference performed during signature resolution or `infer` type resolution
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Backlog

Description

@falsandtru
falsandtru (falsandtru)
opened on Mar 13, 2020

TypeScript Version: 3.0.0-dev.20200312

Search Terms:

Code

export interface Supervisor<N extends string, P = undefined, R = P, S = undefined> {
  constructor: typeof Supervisor;
}
export abstract class Supervisor<N extends string, P = undefined, R = P, S = undefined> {
  constructor() {
    if (this.constructor === Supervisor) this.id;
  }
  public id = 0;
  public abstract call(name: N | ('' extends N ? undefined | ((names: Iterable<N>) => Iterable<N>) : never), param: P, timeout?: number): Promise<R>;
}

Expected behavior:
pass
Actual behavior:
Property 'id' does not exist on type 'never'.(2339)
Playground Link: http://www.typescriptlang.org/play/index.html?ts=3.9.0-dev.20200312&ssl=1&ssc=1&pln=10&pc=2#code/KYDwDg9gTgLgBASwHY2FAZgQwMbDgZQFcw0A3BAZ2gB4A5OUVJAEwrgpimQHMAaOAApwAvHEItg6ZMGb8ASiMH98i8c0nTmAPjgBvAFBw42CEg5RC2GNABccGAE8SEdAWJlK0ANz6AvvtBIWDhMACNzHHhsABtMCjYiEihyKig6BhAmVnZOHn4hUTUNJBl5RQFlVQkpEu09Q2NTc0trKAAKAEp6oyMEVzaYAAtKADoTM04W6BFhUUSPVK6h0YRmHyN-IzBCUOiEbERmRQAGdbht3f2Q8M5I40xo6LakTABbYDt6AB84NoByP4ZLJsegAfjE1U0cB+bWeb2AFDsAElUFAwtFgHQtF1hDoUWh0ZjaNi4HYSqQ0B1+GBMGjXnYKvYEO8IIQYKCyYRXqFKQyoBBXpRMXItD5fEA

Related Issues:

Activity

  1. Ryan Cavanaugh (RyanCavanaugh)
    added
    BugA bug in TypeScript
    on Mar 17, 2020
  2. Ryan Cavanaugh (RyanCavanaugh)
    added this to the Backlog milestone on Mar 17, 2020

  3. RyanCavanaugh commented on Mar 17, 2020

    @RyanCavanaugh
    Ryan Cavanaugh (RyanCavanaugh)
    on Mar 17, 2020
    Member

    Simplified a bit:

    interface SomeClass<N> {
  constructor: typeof SomeClass;
}
abstract class SomeClass<N> {
  constructor() {
    if (this.constructor === SomeClass) this.id;
  }
  public id = 0;
  public abstract foo(name: ('' extends N ? undefined: null)): any;
}

  4. hikarino-my commented on Mar 24, 2020

    @hikarino-my
    M.Yoshimura (hikarino-my)
    on Mar 24, 2020
    Contributor

    Seems to be appearing after #32774

  5. Ryan Cavanaugh (RyanCavanaugh)
    added
    Domain: check: Type InferenceRelated to type inference performed during signature resolution or `infer` type resolution
    on Oct 16, 2025
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