Refactor.

src/api/custom_syntax.rs

@@ -147,6 +147,7 @@ impl Expression<'_> {
 
 impl AsRef<Expr> for Expression<'_> {
     #[inline(always)]
+    #[must_use]
     fn as_ref(&self) -> &Expr {
         self.0
     }
@@ -156,6 +157,7 @@ impl Deref for Expression<'_> {
     type Target = Expr;
 
     #[inline(always)]
+    #[must_use]
     fn deref(&self) -> &Self::Target {
         self.0
     }

src/api/mod.rs

@@ -75,6 +75,7 @@ impl Engine {
     /// Not available under `no_module`.
     #[cfg(not(feature = "no_module"))]
     #[inline(always)]
+    #[must_use]
     pub fn module_resolver(&self) -> &dyn crate::ModuleResolver {
         &*self.module_resolver
     }

src/api/register.rs

@@ -16,12 +16,14 @@ impl Engine {
     /// Get the global namespace module (which is the fist module in `global_modules`).
     #[inline(always)]
     #[allow(dead_code)]
+    #[must_use]
     pub(crate) fn global_namespace(&self) -> &Module {
         self.global_modules.first().unwrap()
     }
     /// Get a mutable reference to the global namespace module
     /// (which is the first module in `global_modules`).
     #[inline(always)]
+    #[must_use]
     pub(crate) fn global_namespace_mut(&mut self) -> &mut Module {
         let module = self.global_modules.first_mut().unwrap();
         Shared::get_mut(module).expect("not shared")