TS2428

error TS2428: All declarations of ‘Strategy’ must have identical type parameters.

Bad Code ❌

Strategy.ts

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enum TOPIC {
ON_LOGOUT = 'ON_LOGOUT',
}

export interface Strategy {
on(event: TOPIC.ON_LOGOUT, listener: (reason: string) => void): this;
}

export abstract class Strategy<SpecificConfig extends StrategyConfig> extends EventEmitter {
// ...
}

Fixed Code ✔️

Solution: The generic abstract class Strategy has a generic type parameter list in angle brackets (diamond notation). This generic type parameter list must also be added to the interface definition of Strategy.

Strategy.ts

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enum TOPIC {
ON_LOGOUT = 'ON_LOGOUT',
}

export interface Strategy<SpecificConfig extends StrategyConfig> {
on(event: TOPIC.ON_LOGOUT, listener: (reason: string) => void): this;
}

export abstract class Strategy<SpecificConfig extends StrategyConfig> extends EventEmitter {
// ...
}