Type Alias ClosureFn 

pub type ClosureFn = Box<dyn Fn(&[Value]) -> Result<Value, SoilError>>;

A Soil closure, as a boxed Rust callable (resolved decision, impl plan §1): plan-01 tests and builtins pass Rust closures, soil0’s interpreter captures AST + environment, compiled code later wraps an extern "C" function and its environment. One invocation path.

Aliased Type

pub struct ClosureFn(/* private fields */);