unsafe fn env_binding(env: SEXP, name: &str) -> Option<SEXP>Expand description
Look up a variable bound directly in a single environment frame (no search
of enclosing frames) with REnv::get.
Returns None for a non-environment, an absent binding, or NULL (none
can hold a class handle). Promises and active bindings are evaluated once;
their errors unwind to the caller’s miniextendr boundary.
§Safety
R’s main thread, inside a miniextendr boundary.