@baldwindavid 's explanation is nice and correct. (Thank you! 
)
TypeCheck cannot extract the types from already-compiled modules: types are stored in a completely different format inside the BEAM, are not always available, and are difficult to parse. Some libraries which are making steps in parsing them do exist (such as Mavis) although they are not very mature at this time and as such are not integrated with TypeCheck either.
For now, either add the types you’re using directly in your modules, or use the ‘remote type overrides’ as mentioned by @baldwindavid.
My hope is that we will have integration with common libraries in the near future, but that will take some time/effort.
!
