Add a type-level typeof operator #2082
Description
Similar to typescript's https://www.typescriptlang.org/docs/handbook/2/typeof-types.html it would be nice to be able to have a type-level typeof operator that would be used to ascribe a type to a variable using the type of an existing variable. Especially useful if you're using a projector or external data to get some data but don't have a type declaration.