Type Alias OnlyOneRecord<K, V>

OnlyOneRecord: {
    [P in K]: (Record<P, V> & Partial<Record<Exclude<K, P>, never>>) extends infer O
        ? { [Q in keyof O]: O[Q] }
        : never
}[K]

Constructs a type in which only one key in K can have the value in V.

// Error
const ex1: OnlyOneRecord<'a' | 'b', { 1: 1 }> = {
  a: { 1: 1 },
  b: { 1: 1 }
};
// Ok
const ex2: OnlyOneRecord<'a' | 'b', { 1: 1 }> = {
  b: { 1: 1 }
};

Type Parameters

K extends string
V = any

Type Alias OnlyOneRecord<K, V>

Type Parameters

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