How to exclude a void type on a union type?

Issue

Hello guys I have a custom generic type P that is defined like this P extends Record<string, unknown> | void

And I want to have an exists function

export class Parameters<P extends Record<string, unknown> | void> {
        private params: P
        constructor(params: P) {
                this.params = params 
        }
        public exists(field: keyof P): boolean {
                return field in this.params
        }
}

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But I obviously got a compilation error when running a tsc because I can't do it on the void type. How can I get rid of it inside my exists function?

tsc Typescript version 4.9.3 Thanks!

Solution

First make sure params in not undefined

export class Parameters<P extends Record<string, unknown> | void> {
    params!: P
    public exists(field: P): boolean {
        return this.params && field in this.params
    }
}

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Answered By - Dimava