Check for missing docs.

src/func/func.rs

@@ -13,6 +13,7 @@ use std::prelude::v1::*;
 ///
 /// Not available under `no_function`.
 pub trait Func<ARGS, RET> {
+    /// The closure's output type.
     type Output;
 
     /// Create a Rust closure from an [`AST`].

src/func/plugin.rs

@@ -10,6 +10,7 @@ pub use crate::{
 use std::prelude::v1::*;
 pub use std::{any::TypeId, mem};
 
+/// Result of a Rhai function.
 pub type RhaiResult = crate::RhaiResult;
 
 #[cfg(not(features = "no_module"))]