Class that implements an interface does not get type inference on method arguments.

[nicksrandall]

TypeScript Version: 4.0.5

Search Terms:
Class that implements an interface does not get type inference on method arguments.

Code

interface Component<A> {
  render(settings: A): string;
}

type HelloSettings = {
  greeting: string;
};

class GreetingComponent implements Component<HelloSettings> {
  render(settings) {
    return settings.greeting;
  }
}

Expected behavior:
I would expect the settings argument in render method of the "GreetingComponent" to have an inferred type of HelloSettings but currently that argument is inferred as any.

Actual behavior:
The settings argument in the render method of the "GreetingComponent" has an inferred type of any.

Playground Link:
https://www.typescriptlang.org/play?#code/JYOwLgpgTgZghgYwgAgMIHsC2AHdILgA8AggHzIDeAUMslAQCbQAUAzhGGKAOasBcyYgEoBrMFB4BuKgF8qVMAE9sKABIQANhvQBlDlxC9kAXko1k3ehx6jxU2dKoINcVq2QBxKwe4YceAjBkYBwNCExA9z9cfCJ1LV19HlZyalp6ECYoNiTDViEzWnSOAFcoEGR2TmSAOksIa0NpWjkZIA

Related Issues:

[RyanCavanaugh]

See #10570 / #6118 / #1373 / others

[typescript-bot]

This issue has been marked as a 'Duplicate' and has seen no recent activity. It has been automatically closed for house-keeping purposes.