Type assertions using Exact, Subset, Superset

I have suffered several times with the limitations of casting like so:

res.json(<Foo>{foo:'bar'});

the above cast/assertion will work even if the anonymous object does not have all the fields in type Foo.
For example, this question I had: https://stackoverflow.com/questions/53328459/prevent-compilation-unless-all-fields-exist

This feature request is for something like this:

res.json(Exact<Foo>{foo:'bar'});
res.json(Subset<Foo>{foo:'bar'});
res.json(Superset<Foo>{foo:'bar'});

note this is similar to the existing construct Partial, as in Partial<T>, hopefully the above are self-explanatory. I am not sure if both Subset<> and Superset<> make sense, but one of them should.

Start by reviewing the proposed Exact, Subset, and Superset type-assertion syntax and compare it with the existing Partial construct. Define which semantics are required, including whether both Subset and Superset are needed; the issue names no files, tests, or entry points, so completion would require establishing the design and its validation criteria.