support boxed Iterator in Option

1 files changed, 10 insertions, 3 deletions

diff --git a/src/transform.rs b/src/transform.rs
index fff9c6c..69929cc 100644
--- a/src/transform.rs
+++ b/src/transform.rs
@@ -9,7 +9,7 @@ use syn::{
 
 use crate::{
     filter_map_assoc_paths, match_assoc_type,
-    parse_assoc_type::DestType,
+    parse_assoc_type::{BoxType, DestType},
     parse_trait_sig::{MethodParseError, TypeTransform},
     syn_utils::{iter_path, iter_type},
 };
@@ -56,8 +56,15 @@ impl AssocTypeConversions<'_> {
                                             {
                                                 let inner =
                                                     self.parse_type_path(&mut binding.ty)?;
-                                                *type_ = Type::Verbatim(quote! {Box<#elem + '_>});
-                                                return Ok(TypeTransform::Iterator(inner.into()));
+                                                let box_type = BoxType {
+                                                    inner: quote! {#elem},
+                                                    placeholder_lifetime: true,
+                                                };
+                                                *type_ = Type::Verbatim(quote! {#box_type});
+                                                return Ok(TypeTransform::Iterator(
+                                                    box_type,
+                                                    inner.into(),
+                                                ));
                                             }
                                         }
                                     }