Reduce usage of as_ref and as_mut.

src/module/resolvers/collection.rs

@@ -1,7 +1,7 @@
 use crate::{Engine, Module, ModuleResolver, Position, RhaiResultOf, Shared, ERR};
 #[cfg(feature = "no_std")]
 use std::prelude::v1::*;
-use std::{ops::AddAssign, vec::IntoIter};
+use std::{ops::AddAssign, slice::Iter, vec::IntoIter};
 
 /// [Module] resolution service that holds a collection of module resolvers,
 /// to be searched in sequential order.
@@ -116,6 +116,16 @@ impl IntoIterator for ModuleResolversCollection {
     }
 }
 
+impl<'a> IntoIterator for &'a ModuleResolversCollection {
+    type Item = &'a Box<dyn ModuleResolver>;
+    type IntoIter = Iter<'a, Box<dyn ModuleResolver>>;
+
+    #[inline(always)]
+    fn into_iter(self) -> Self::IntoIter {
+        self.0.iter()
+    }
+}
+
 impl ModuleResolver for ModuleResolversCollection {
     fn resolve(
         &self,

src/module/resolvers/file.rs

@@ -172,7 +172,7 @@ impl FileModuleResolver {
     #[inline(always)]
     #[must_use]
     pub fn base_path(&self) -> Option<&Path> {
-        self.base_path.as_ref().map(PathBuf::as_ref)
+        self.base_path.as_ref().map(<_>::as_ref)
     }
     /// Set the base path for script files.
     #[inline(always)]

src/module/resolvers/stat.rs

@@ -3,7 +3,11 @@ use crate::{
 };
 #[cfg(feature = "no_std")]
 use std::prelude::v1::*;
-use std::{collections::btree_map::IntoIter, collections::BTreeMap, ops::AddAssign};
+use std::{
+    collections::btree_map::{IntoIter, Iter},
+    collections::BTreeMap,
+    ops::AddAssign,
+};
 
 /// A static [module][Module] resolution service that serves [modules][Module] added into it.
 ///
@@ -122,11 +126,22 @@ impl IntoIterator for StaticModuleResolver {
     type Item = (Identifier, Shared<Module>);
     type IntoIter = IntoIter<SmartString, Shared<Module>>;
 
+    #[inline(always)]
     fn into_iter(self) -> Self::IntoIter {
         self.0.into_iter()
     }
 }
 
+impl<'a> IntoIterator for &'a StaticModuleResolver {
+    type Item = (&'a Identifier, &'a Shared<Module>);
+    type IntoIter = Iter<'a, SmartString, Shared<Module>>;
+
+    #[inline(always)]
+    fn into_iter(self) -> Self::IntoIter {
+        self.0.iter()
+    }
+}
+
 impl ModuleResolver for StaticModuleResolver {
     #[inline]
     fn resolve(