From bacdafb4883d8f8ea06e498285c78f82de9a391b Mon Sep 17 00:00:00 2001
From: Martin Fischer <martin@push-f.com>
Date: Mon, 22 Nov 2021 06:36:37 +0100
Subject: support Vec, VecDeque & LinkedList collections

---
 src/lib.rs             |  6 +++++-
 src/parse_trait_sig.rs |  1 +
 src/transform.rs       | 21 +++++++++++++++++++++
 3 files changed, 27 insertions(+), 1 deletion(-)

(limited to 'src')

diff --git a/src/lib.rs b/src/lib.rs
index 1f75023..6a1708f 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -409,7 +409,11 @@ impl TypeTransform {
                     quote! {#arg.map_err(|x| #err_inner)}
                 }
             }
-            _other => arg,
+            TypeTransform::Collection(inner) => {
+                let inner = inner.convert(quote!(x));
+                quote! {#arg.into_iter().map(|x| #inner).collect()}
+            }
+            TypeTransform::NoOp => arg,
         }
     }
 }
diff --git a/src/parse_trait_sig.rs b/src/parse_trait_sig.rs
index ab2c437..c924a71 100644
--- a/src/parse_trait_sig.rs
+++ b/src/parse_trait_sig.rs
@@ -17,6 +17,7 @@ pub enum TypeTransform {
     Into,
     Box(BoxType),
     Map(Box<TypeTransform>),
+    Collection(Box<TypeTransform>),
     Iterator(BoxType, Box<TypeTransform>),
     Result(Box<TypeTransform>, Box<TypeTransform>),
 }
diff --git a/src/transform.rs b/src/transform.rs
index e8481bb..3f1c313 100644
--- a/src/transform.rs
+++ b/src/transform.rs
@@ -22,6 +22,12 @@ pub enum TransformError {
     AssocTypeInUnsupportedType(Span),
 }
 
+fn is_supported_collection(ident: &Ident) -> bool {
+    // collections added here must implement IntoIterator & FromIterator
+    // FromIterator must not require bounds like Eq or Ord since these are Self-referential
+    ident == "Vec" || ident == "VecDeque" || ident == "LinkedList"
+}
+
 impl AssocTypeConversions<'_> {
     pub fn parse_type_path(&self, type_: &mut Type) -> Result<TypeTransform, TransformError> {
         if !iter_type(type_).any(match_assoc_type) {
@@ -120,6 +126,21 @@ impl AssocTypeConversions<'_> {
                         }
                     }
                 }
+            } else if is_supported_collection(ident) && path.segments.len() == 1 {
+                let first_seg = path.segments.first_mut().unwrap();
+
+                if let PathArguments::AngleBracketed(args) = &mut first_seg.arguments {
+                    if args.args.len() == 1 {
+                        if let GenericArgument::Type(generic_type) = args.args.first_mut().unwrap()
+                        {
+                            if iter_type(generic_type).any(match_assoc_type) {
+                                return Ok(TypeTransform::Collection(
+                                    self.parse_type_path(generic_type)?.into(),
+                                ));
+                            }
+                        }
+                    }
+                }
             } else {
                 let last_seg = &path.segments.last().unwrap();
                 if last_seg.ident == "Result" {
-- 
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