Function dispatch_method_body 

pub fn dispatch_method_body<B>(function: FunctionInstance<B>) -> MethodBody
where
    B: FunctionBodyPolicy,

Projects a function instance into a dispatch method body.

This adapter is deliberately opt-in: FunctionInstance remains a kernel callable in its own right, and an ordinary call never constructs or consults a generic function. Dispatch supplies only method selection; after selection, the same neutral call boundary invokes the same guest policy.