Check for duplicate keys in different Go Map types

Question content

I want a function to check for duplicate keys in different maps.

This is what I have

ma := map[string]typea
mb := map[string]typeb
mc := map[string]typec

dup := map[string]bool{}
    for k := range ma{
        if !dup[k] {
            dup[k] = true
        } else {
            return fmt.errorf("duplicate key[%v]", k)
        }
    }
    for k := range mb{
        if !dup[k] {
            dup[k] = true
        } else {
            return fmt.errorf("duplicate key[%v]", k)
        }
    }
    for k := range mc {
        if !dup[k] {
            dup[k] = true
        } else {
            return fmt.errorf("duplicate key[%v]", k)
        }
    }
    return nil

I want to refactor it and write a function

func checkDupKeys[M ~map[K]V, K comparable, V any](maps ...M) error {
    dup := map[K]bool{}
    for _, m := range maps {
        for k := range m {
            if !dup[k] {
                dup[k] = true
            } else {
                return fmt.Errorf("duplicate key[%v]", k)
            }
        }
    }
    return nil
}

But it can only accept mappings of the same type, not typea, typeb and typec.

Correct answer

You can try using any types and reflection

func checkDupKeys(maps ...any) error {
    dup := map[any]bool{}
    for i, m := range maps {
        t := reflect.TypeOf(m)
        if t.Kind() != reflect.Map {
            return fmt.Errorf("not a map at index: %d", i)
        }
        keys := reflect.ValueOf(m).MapKeys()
        for _, k := range keys {
            v := k.Interface()
            if !dup[v] {
                dup[v] = true
            } else {
                return fmt.Errorf("duplicate key[%v]", v)
            }
        }
    }
    return nil
}

The disadvantage of this approach is that the function will also accept non-mapped parameters, and the compiler will not warn about this.

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