From 419f34c6657ca6badc456451d20317aa7c738414 Mon Sep 17 00:00:00 2001
From: Erick Tryzelaar <erick.tryzelaar@gmail.com>
Date: Sun, 8 Mar 2015 18:46:41 -0700
Subject: [PATCH] Fix #[derive_deserialize] for generic structs

---
 serde2/serde2_macros/src/lib.rs | 59 ++++++++++++++++++++++++++++-----
 serde2/tests/test_macros.rs     | 49 ++++++++++++++++++++++-----
 2 files changed, 91 insertions(+), 17 deletions(-)

diff --git a/serde2/serde2_macros/src/lib.rs b/serde2/serde2_macros/src/lib.rs
index 8dfa8209..c891e75c 100644
--- a/serde2/serde2_macros/src/lib.rs
+++ b/serde2/serde2_macros/src/lib.rs
@@ -729,7 +729,8 @@ fn deserialize_struct(
                 struct_path,
                 &fields,
                 state,
-                struct_def)
+                struct_def,
+                generics)
         }
     }
 }
@@ -919,14 +920,56 @@ fn deserialize_struct_named_fields(
     fields: &[(Ident, Span)],
     state: P<ast::Expr>,
     struct_def: &StructDef,
+    generics: &ast::Generics,
 ) -> P<ast::Expr> {
-    let struct_name = builder.expr().str(struct_ident);
+    let visitor_impl_generics = builder.from_generics(generics.clone())
+        .add_ty_param_bound(
+            builder.path().global().ids(&["serde2", "de", "Deserialize"]).build()
+        )
+        .build();
 
     // Create the field names for the fields.
     let field_names: Vec<ast::Ident> = (0 .. fields.len())
         .map(|i| token::str_to_ident(&format!("__field{}", i)))
         .collect();
 
+    // Build `__Visitor<A, B, ...>(PhantomData<A>, PhantomData<B>, ...)`
+    let (visitor_struct, visitor_expr) = if generics.ty_params.is_empty() {
+        (
+            builder.item().tuple_struct("__Visitor")
+                .build(),
+            builder.expr().id("__Visitor"),
+        )
+    } else {
+        (
+            builder.item().tuple_struct("__Visitor")
+                .generics().with(generics.clone()).build()
+                .with_tys(
+                    generics.ty_params.iter().map(|ty_param| {
+                        builder.ty().phantom_data().id(ty_param.ident)
+                    })
+                )
+                .build(),
+            builder.expr().call().id("__Visitor")
+                .with_args(
+                    generics.ty_params.iter().map(|_| {
+                        builder.expr().phantom_data()
+                    })
+                )
+                .build(),
+        )
+    };
+
+    let struct_name = builder.expr().str(struct_ident);
+
+    let visitor_ty = builder.ty().path()
+        .segment("__Visitor").with_generics(generics.clone()).build()
+        .build();
+
+    let value_ty = builder.ty().path()
+        .segment(type_ident).with_generics(generics.clone()).build()
+        .build();
+
     let field_deserializer = declare_map_field_deserializer(
         cx,
         span,
@@ -948,13 +991,13 @@ fn deserialize_struct_named_fields(
     quote_expr!(cx, {
         $field_deserializer
 
-        struct __Visitor;
+        $visitor_struct;
 
-        impl ::serde2::de::Visitor for __Visitor {
-            type Value = $type_ident;
+        impl $visitor_impl_generics ::serde2::de::Visitor for $visitor_ty {
+            type Value = $value_ty;
 
             #[inline]
-            fn visit_map<__V>(&mut self, mut visitor: __V) -> Result<$type_ident, __V::Error>
+            fn visit_map<__V>(&mut self, mut visitor: __V) -> Result<$value_ty, __V::Error>
                 where __V: ::serde2::de::MapVisitor,
             {
                 $visit_map_expr
@@ -963,7 +1006,7 @@ fn deserialize_struct_named_fields(
             #[inline]
             fn visit_named_map<__V>(&mut self,
                                     name: &str,
-                                    visitor: __V) -> Result<$type_ident, __V::Error>
+                                    visitor: __V) -> Result<$value_ty, __V::Error>
                 where __V: ::serde2::de::MapVisitor,
             {
                 if name == $struct_name {
@@ -974,7 +1017,7 @@ fn deserialize_struct_named_fields(
             }
         }
 
-        $state.visit(__Visitor)
+        $state.visit($visitor_expr)
     })
 }
 
diff --git a/serde2/tests/test_macros.rs b/serde2/tests/test_macros.rs
index 30a73e66..6c8770c1 100644
--- a/serde2/tests/test_macros.rs
+++ b/serde2/tests/test_macros.rs
@@ -30,14 +30,6 @@ trait Trait {
 #[derive_deserialize]
 struct NamedUnit;
 
-#[derive(Debug, PartialEq)]
-#[derive_serialize]
-struct NamedMap<'a, 'b, A: 'a, B: 'b, C> {
-    a: &'a A,
-    b: &'b mut B,
-    c: C,
-}
-
 #[derive(Debug, PartialEq)]
 #[derive_serialize]
 //#[derive_deserialize]
@@ -126,7 +118,15 @@ fn test_de_named_tuple() {
 }
 
 #[test]
-fn test_named_map() {
+fn test_ser_named_map() {
+    #[derive(Debug, PartialEq)]
+    #[derive_serialize]
+    struct NamedMap<'a, 'b, A: 'a, B: 'b, C> {
+        a: &'a A,
+        b: &'b mut B,
+        c: C,
+    }
+
     let a = 5;
     let mut b = 6;
     let c = 7;
@@ -151,6 +151,37 @@ fn test_named_map() {
     );
 }
 
+#[test]
+fn test_de_named_map() {
+    #[derive(Debug, PartialEq)]
+    #[derive_deserialize]
+    struct NamedMap<A, B, C> {
+        a: A,
+        b: B,
+        c: C,
+    }
+
+    let v = NamedMap {
+        a: 5,
+        b: 6,
+        c: 7,
+    };
+
+    assert_eq!(
+        json::from_str("{\"a\":5,\"b\":6,\"c\":7}").unwrap(),
+        v
+    );
+
+    assert_eq!(
+        json::from_value(Value::Object(btreemap![
+            "a".to_string() => Value::I64(5),
+            "b".to_string() => Value::I64(6),
+            "c".to_string() => Value::I64(7)
+        ])).unwrap(),
+        v
+    );
+}
+
 #[test]
 fn test_enum_unit() {
     assert_eq!(