diff --git a/src/Fable.Transforms/Rust/Fable2Rust.fs b/src/Fable.Transforms/Rust/Fable2Rust.fs
index 1c956e59f..6d72fbd2a 100644
--- a/src/Fable.Transforms/Rust/Fable2Rust.fs
+++ b/src/Fable.Transforms/Rust/Fable2Rust.fs
@@ -436,7 +436,8 @@ module TypeInfo =
         | _ -> isTypeOfType com isDefaultableType isDefaultableEntity entNames typ
 
     let isDefaultableEntity com entNames (ent: Fable.Entity) =
-        not (ent.IsInterface)
+        ent.IsValueType
+        && not (ent.IsInterface)
         && not (ent.IsFSharpUnion) // deriving 'Default' on enums is experimental
         && (isEntityOfType com isDefaultableType entNames ent)
 
@@ -4046,7 +4047,7 @@ module Util =
 
         loop body
 
-    let makeAssocMemberItem
+    let makeMemberAssocItem
         com
         ctx
         (memb: Fable.MemberFunctionOrValue)
@@ -4393,7 +4394,7 @@ module Util =
                 else
                     None
 
-            makeAssocMemberItem com ctx memb args bodyOpt
+            makeMemberAssocItem com ctx memb args bodyOpt
         )
 
     let transformInterface (com: IRustCompiler) ctx (ent: Fable.Entity) (decl: Fable.ClassDecl) =
@@ -4664,12 +4665,19 @@ module Util =
     //             "ToString"
     //         ]
 
-    let ignoredInterfaceNames = set [ Types.ienumerable; Types.ienumerator ]
+    let findInterfaceGenArgs (com: IRustCompiler) (ent: Fable.Entity) (ifcEntRef: Fable.EntityRef) =
+        let ifcOpt =
+            ent.AllInterfaces
+            |> Seq.tryFind (fun ifc -> ifc.Entity.FullName = ifcEntRef.FullName)
 
-    let getDeclaringEntities (members: Fable.MemberFunctionOrValue list) =
-        members
-        |> List.choose (fun memb -> memb.DeclaringEntity)
-        |> List.distinctBy (fun entRef -> entRef.FullName)
+        match ifcOpt with
+        | Some ifc -> ifc.GenericArgs
+        | _ ->
+            // shouldn't really happen
+            let ifcEnt = com.GetEntity(ifcEntRef)
+            FSharp2Fable.Util.getEntityGenArgs ifcEnt
+
+    let ignoredInterfaceNames = set [ Types.ienumerable; Types.ienumerator ]
 
     let transformClassMembers (com: IRustCompiler) ctx genArgs (classDecl: Fable.ClassDecl) =
         let entRef = classDecl.Entity
@@ -4735,19 +4743,18 @@ module Util =
 
         let interfaceTraitImpls =
             interfaceMembers
-            |> List.map snd
-            |> getDeclaringEntities
+            |> List.choose (fun (d, m) -> m.DeclaringEntity)
+            |> List.distinctBy (fun ifcEntRef -> ifcEntRef.FullName)
             |> List.filter (fun ifcEntRef ->
                 // throws out anything on the ignored interfaces list
                 not (ignoredInterfaceNames |> Set.contains ifcEntRef.FullName)
             )
             |> List.collect (fun ifcEntRef ->
                 let ifcGenArgs =
-                    if ent.IsInterface then
+                    if isObjectExpr then
                         genArgs
                     else
-                        let ifcEnt = com.GetEntity(ifcEntRef)
-                        FSharp2Fable.Util.getEntityGenArgs ifcEnt
+                        ifcEntRef |> findInterfaceGenArgs com ent
 
                 let memberNames = getInterfaceMemberNames com ifcEntRef
 
diff --git a/src/fable-library-rust/src/HashMap.rs b/src/fable-library-rust/src/HashMap.rs
index cbcb1a8eb..f265d033d 100644
--- a/src/fable-library-rust/src/HashMap.rs
+++ b/src/fable-library-rust/src/HashMap.rs
@@ -25,14 +25,14 @@ pub mod HashMap_ {
         comparer: LrcPtr<dyn IEqualityComparer_1<K>>,
     }
 
-    impl<K, V: Clone> Default for HashMap<K, V>
-    where
-        K: Clone + Hash + PartialEq + 'static,
-    {
-        fn default() -> HashMap<K, V> {
-            new_empty()
-        }
-    }
+    // impl<K, V: Clone> Default for HashMap<K, V>
+    // where
+    //     K: Clone + Hash + PartialEq + 'static,
+    // {
+    //     fn default() -> HashMap<K, V> {
+    //         new_empty()
+    //     }
+    // }
 
     impl<K: Clone, V: Clone> core::ops::Deref for HashMap<K, V> {
         type Target = Lrc<MutHashMap<K, V>>;
diff --git a/src/fable-library-rust/src/HashSet.rs b/src/fable-library-rust/src/HashSet.rs
index 7abd807e3..1d8ed593b 100644
--- a/src/fable-library-rust/src/HashSet.rs
+++ b/src/fable-library-rust/src/HashSet.rs
@@ -25,14 +25,14 @@ pub mod HashSet_ {
         comparer: LrcPtr<dyn IEqualityComparer_1<T>>,
     }
 
-    impl<T> Default for HashSet<T>
-    where
-        T: Clone + Hash + PartialEq + 'static,
-    {
-        fn default() -> HashSet<T> {
-            new_empty()
-        }
-    }
+    // impl<T> Default for HashSet<T>
+    // where
+    //     T: Clone + Hash + PartialEq + 'static,
+    // {
+    //     fn default() -> HashSet<T> {
+    //         new_empty()
+    //     }
+    // }
 
     impl<T: Clone> core::ops::Deref for HashSet<T> {
         type Target = Lrc<MutHashSet<T>>;