Function check_with 

pub fn check_with(
    package: &Package,
    program: &Program,
    schemas: &HostSchemas,
) -> Vec<Diagnostic>

Type-checks a resolved program against schemas, the host modules this compilation may name.

This is check with the one thing an embedder can change. A module in schemas is checked exactly as a shipped one is: its operations’ arity, argument types, and results; the fields of the types it declares; the cases of its enums; and the operations its resources answer.