interface Orig<T extends string> {
    type: T;
}

type TypeId = 'SpecA';

interface SpecA extends Orig<TypeId> {
    name?: string;
}

const goodCast = <SpecA>{
    type: 'SpecA'
}

const badCast = <SpecA>{
    type: 'SpecB'
}
// throws an error:
// Type '{ type: "SpecB"; }' cannot be converted to type 'SpecA'.
//  Types of property 'type' are incompatible.
//    Type '"SpecB"' is not comparable to type '"SpecA"'.

const justData = {
    type: 'SpecB'
};

const castLater = <SpecA>justData;
// Expected an error to be thrown, but the compiler accepts this.