Fix hygiene of macro-generated local variable accesses in serde(with) wrappers

Author: dtolnay

serde_derive/src/de.rs

@@ -2882,13 +2882,14 @@ fn wrap_deserialize_with(
     let (de_impl_generics, de_ty_generics, ty_generics, where_clause) =
         split_with_de_lifetime(params);
     let delife = params.borrowed.de_lifetime();
+    let deserializer_var = quote!(__deserializer);
 
     // If #deserialize_with returns wrong type, error will be reported here (^^^^^).
     // We attach span of the path to the function so it will be reported
     // on the #[serde(with = "...")]
     //                       ^^^^^
     let value = quote_spanned! {deserialize_with.span()=>
-        #deserialize_with(__deserializer)?
+        #deserialize_with(#deserializer_var)?
     };
     let wrapper = quote! {
         #[doc(hidden)]
@@ -2899,7 +2900,7 @@ fn wrap_deserialize_with(
         }
 
         impl #de_impl_generics _serde::Deserialize<#delife> for __DeserializeWith #de_ty_generics #where_clause {
-            fn deserialize<__D>(__deserializer: __D) -> _serde::__private::Result<Self, __D::Error>
+            fn deserialize<__D>(#deserializer_var: __D) -> _serde::__private::Result<Self, __D::Error>
             where
                 __D: _serde::Deserializer<#delife>,
             {

serde_derive/src/ser.rs

@@ -1220,12 +1220,15 @@ fn wrap_serialize_with(
         })
     });
 
+    let self_var = quote!(self);
+    let serializer_var = quote!(__s);
+
     // If #serialize_with returns wrong type, error will be reported on here.
     // We attach span of the path to this piece so error will be reported
     // on the #[serde(with = "...")]
     //                       ^^^^^
     let wrapper_serialize = quote_spanned! {serialize_with.span()=>
-        #serialize_with(#(self.values.#field_access, )* __s)
+        #serialize_with(#(#self_var.values.#field_access, )* #serializer_var)
     };
 
     quote!({
@@ -1236,7 +1239,7 @@ fn wrap_serialize_with(
         }
 
         impl #wrapper_impl_generics _serde::Serialize for __SerializeWith #wrapper_ty_generics #where_clause {
-            fn serialize<__S>(&self, __s: __S) -> _serde::__private::Result<__S::Ok, __S::Error>
+            fn serialize<__S>(&#self_var, #serializer_var: __S) -> _serde::__private::Result<__S::Ok, __S::Error>
             where
                 __S: _serde::Serializer,
             {

test_suite/tests/ui/with/incorrect_type.stderr

@@ -19,8 +19,10 @@ note: required by a bound in `w::serialize`
 error[E0061]: this function takes 1 argument but 2 arguments were supplied
   --> tests/ui/with/incorrect_type.rs:15:25
    |
+14 | #[derive(Serialize, Deserialize)]
+   |          --------- unexpected argument #2 of type `__S`
 15 | struct W(#[serde(with = "w")] u8, u8);
-   |                         ^^^ unexpected argument #2 of type `__S`
+   |                         ^^^
    |
 note: function defined here
   --> tests/ui/with/incorrect_type.rs:9:12
@@ -68,8 +70,10 @@ note: required by a bound in `w::serialize`
 error[E0061]: this function takes 1 argument but 2 arguments were supplied
   --> tests/ui/with/incorrect_type.rs:18:35
    |
+17 | #[derive(Serialize, Deserialize)]
+   |          --------- unexpected argument #2 of type `__S`
 18 | struct S(#[serde(serialize_with = "w::serialize")] u8, u8);
-   |                                   ^^^^^^^^^^^^^^ unexpected argument #2 of type `__S`
+   |                                   ^^^^^^^^^^^^^^
    |
 note: function defined here
   --> tests/ui/with/incorrect_type.rs:9:12