Static type checking is performed against external data sources in an interacting editing environment. A rich editing experience can be provided to users for external data equivalent to that provided for internal static, typed data. An extensible compiler is provided so that a user or third party can extend type checking facilities to any external data source. An extensible language service is provided so that a user or third party can extend the language service to provide a consistent, current static view of external data. The extensible compiler and language service allow language extensions to plug into the type checking process. This enables the compiler and language service to provide an extension point that allows extensions of the compiler and allow the language service to render dynamic information statically.