Function check_only 

pub fn check_only(
    source: String,
    filename: &str,
    resolver: &ImportResolver,
) -> CompileOutput

compile_checked as a check only, which opens no library.

A dylib block binds the signatures it declares, so a script whose C library has not been built yet checks the same as one whose library is in place.

The result type-checks like a full compile but cannot call into a library, so it is for reporting on, not for running or packaging. candela check, Engine::check and the language server compile through here.