You should be able to use the TypeChecker API from the compiler to get to the type information you need. there is no serialization logic readily available, but should be possible to add one.
Here is the TypeChecker API: https://github.com/Microsoft/TypeScript/blob/085f0df4556801c14a4333d6c1d0bab1375586e4/lib/typescript.d.ts#L1027-L1057
Documentation on using the compiler API: https://github.com/Microsoft/TypeScript/wiki/Using-the-Compiler-API
Here is the part of the emitter that emitts this infromation today using the Checker: https://github.com/Microsoft/TypeScript/blob/085f0df4556801c14a4333d6c1d0bab1375586e4/src/compiler/emitter.ts#L5065-L5104