Typed Maps - like interfaces in TypeScript

I would love to see typed Maps in Dart like it is possible in TypeScript.

TypeScript example:

```TypeScript
interface IPerson {
name: string;
age: number;
height?: number;
}

const person: IPerson = {
name: "Max",
age: 26
}
```

I wish Dart would support something like that so i do not have to create a class for it. It could look something like this:

```Dart
interface IPerson {
String name;
int age;
height? double;
}

Map person = {
name: "Max",
age: 26,
}
```