21.2 FFI and extern
extern attributes and contract-level imports.
FFI and extern
FFI and extern owns extern schema and contract import syntax. Mod-level extern shortcuts are deferred—do not invent them in application code because a blog post from 2014 said so.
Execution owns dispatch policy once the language boundary is chosen: Extern dispatch and policy.
Separate declaration from dispatch
Section titled “Separate declaration from dispatch”The interop feature tells you how source code declares a boundary. Dispatch policy covers what the host does after that boundary has been selected. Read both when implementing an integration, but do not use an execution detail to invent a source-level declaration form.