Add convenient functions and operators for Module and module resolvers.

src/module/mod.rs

@@ -33,7 +33,7 @@ use crate::stdlib::{
     fmt, format,
     iter::empty,
     num::NonZeroUsize,
-    ops::{Deref, DerefMut},
+    ops::{Add, AddAssign, Deref, DerefMut},
     string::{String, ToString},
     vec::Vec,
 };
@@ -1546,6 +1546,38 @@ impl From<StaticVec<(String, Position)>> for ModuleRef {
     }
 }
 
+impl Add<Module> for Module {
+    type Output = Self;
+
+    fn add(self, rhs: Module) -> Self::Output {
+        let mut module = self.clone();
+        module.merge(&rhs);
+        module
+    }
+}
+
+impl Add<&Module> for Module {
+    type Output = Self;
+
+    fn add(self, rhs: &Module) -> Self::Output {
+        let mut module = self.clone();
+        module.merge(rhs);
+        module
+    }
+}
+
+impl AddAssign<Module> for Module {
+    fn add_assign(&mut self, rhs: Module) {
+        self.combine(rhs);
+    }
+}
+
+impl AddAssign<&Module> for Module {
+    fn add_assign(&mut self, rhs: &Module) {
+        self.merge(rhs);
+    }
+}
+
 impl ModuleRef {
     pub(crate) fn index(&self) -> Option<NonZeroUsize> {
         self.1