Allow imported types to be declared more than once

Author: eggyal

crates/cli-support/src/webidl/mod.rs

@@ -1088,7 +1088,12 @@ impl<'a> Context<'a> {
     ) -> Result<(), Error> {
         let import = self.determine_import(import, &type_.name)?;
         log::debug!("inserting import id {:x?}: {}", type_.id, type_.name);
-        assert!(self.aux.internal_refs.insert(type_.id, Referenceable::Import(import.clone())).is_none());
+        let parent = Referenceable::Import(import.clone());
+        match self.aux.internal_refs.insert(type_.id, parent) {
+            Some(Referenceable::Struct(_)) => unreachable!(),
+            Some(Referenceable::Import(previous)) => assert_eq!(previous, import),
+            None => (),
+        }
 
         let (import_id, _id) = match self.function_imports.get(type_.instanceof_shim) {
             Some(pair) => *pair,