Typescript compilation fails for DTO with Dictionary<Enum, string> property

[Shaddix]

The following property in DTO:

public Dictionary<DateTimeKind, string> EnumDictionary { get; set; }

Generates the following piece of code in toJSON method:

        if (this.enumDictionary) {
            data["enumDictionary"] = {};
            for (let key in this.enumDictionary) {
                if (this.enumDictionary.hasOwnProperty(key))
                    (<any>data["enumDictionary"])[key] = this.enumDictionary[key];
            }
        }

Typescript complains:

error TS7053: Element implicitly has an 'any' type because expression of type 'string' can't be used to index type '{ readonly Unspecified?: string | undefined; readonly Utc?: string | undefined; readonly Local?: string | undefined; }'.
  No index signature with a parameter of type 'string' was found on type '{ readonly Unspecified?: string | undefined; readonly Utc?: string | undefined; readonly Local?: string | undefined; }'.

2217                     (<any>data["enumDictionary"])[key] = this.enumDictionary[key];
                                                              ~~~~~~~~~~~~~~~~~~~~~~~~

Apparantely, typescript assumes key is of type string.

[Shaddix]

I guess the easiest fix is to change

(<any>data["enumDictionary"])[key] = this.enumDictionary[key];

into

(<any>data["enumDictionary"])[key] = (<any>this.enumDictionary)[key];

But if you prefer, it could also be fixed by properly typing the key:

data["enumDictionary"] = {};
let key: keyof typeof this.enumDictionary;
for (key in this.enumDictionary) {