From c4a07ed4e80c5db43293526798f5d1ba580351f5 Mon Sep 17 00:00:00 2001
From: Mingun <Alexander_Sergey@mail.ru>
Date: Sat, 20 Sep 2025 00:10:10 +0500
Subject: [PATCH] Move body generator for unit structs to its own module

Cut-paste
---
 serde_derive/src/de.rs      | 49 ++---------------------------------
 serde_derive/src/de/unit.rs | 51 +++++++++++++++++++++++++++++++++++++
 2 files changed, 53 insertions(+), 47 deletions(-)
 create mode 100644 serde_derive/src/de/unit.rs

diff --git a/serde_derive/src/de.rs b/serde_derive/src/de.rs
index 48d2b57c..b20c840e 100644
--- a/serde_derive/src/de.rs
+++ b/serde_derive/src/de.rs
@@ -19,6 +19,7 @@ mod enum_internally;
 mod enum_untagged;
 mod struct_;
 mod tuple;
+mod unit;
 
 pub fn expand_derive_deserialize(input: &mut syn::DeriveInput) -> syn::Result<TokenStream> {
     replace_receiver(input);
@@ -317,7 +318,7 @@ fn deserialize_body(cont: &Container, params: &Parameters) -> Fragment {
             Data::Struct(Style::Tuple, fields) | Data::Struct(Style::Newtype, fields) => {
                 tuple::deserialize_tuple(params, fields, &cont.attrs, TupleForm::Tuple)
             }
-            Data::Struct(Style::Unit, _) => deserialize_unit_struct(params, &cont.attrs),
+            Data::Struct(Style::Unit, _) => unit::deserialize_unit_struct(params, &cont.attrs),
         }
     } else {
         match &cont.data {
@@ -438,52 +439,6 @@ fn deserialize_try_from(type_try_from: &syn::Type) -> Fragment {
     }
 }
 
-/// Generates `Deserialize::deserialize` body for a `struct Unit;`
-fn deserialize_unit_struct(params: &Parameters, cattrs: &attr::Container) -> Fragment {
-    let this_type = &params.this_type;
-    let this_value = &params.this_value;
-    let type_name = cattrs.name().deserialize_name();
-    let (de_impl_generics, de_ty_generics, ty_generics, where_clause) = params.generics();
-    let delife = params.borrowed.de_lifetime();
-
-    let expecting = format!("unit struct {}", params.type_name());
-    let expecting = cattrs.expecting().unwrap_or(&expecting);
-
-    quote_block! {
-        #[doc(hidden)]
-        struct __Visitor #de_impl_generics #where_clause {
-            marker: _serde::#private::PhantomData<#this_type #ty_generics>,
-            lifetime: _serde::#private::PhantomData<&#delife ()>,
-        }
-
-        #[automatically_derived]
-        impl #de_impl_generics _serde::de::Visitor<#delife> for __Visitor #de_ty_generics #where_clause {
-            type Value = #this_type #ty_generics;
-
-            fn expecting(&self, __formatter: &mut _serde::#private::Formatter) -> _serde::#private::fmt::Result {
-                _serde::#private::Formatter::write_str(__formatter, #expecting)
-            }
-
-            #[inline]
-            fn visit_unit<__E>(self) -> _serde::#private::Result<Self::Value, __E>
-            where
-                __E: _serde::de::Error,
-            {
-                _serde::#private::Ok(#this_value)
-            }
-        }
-
-        _serde::Deserializer::deserialize_unit_struct(
-            __deserializer,
-            #type_name,
-            __Visitor {
-                marker: _serde::#private::PhantomData::<#this_type #ty_generics>,
-                lifetime: _serde::#private::PhantomData,
-            },
-        )
-    }
-}
-
 enum TupleForm<'a> {
     Tuple,
     /// Contains a variant name
diff --git a/serde_derive/src/de/unit.rs b/serde_derive/src/de/unit.rs
new file mode 100644
index 00000000..3bce02c3
--- /dev/null
+++ b/serde_derive/src/de/unit.rs
@@ -0,0 +1,51 @@
+use crate::de::Parameters;
+use crate::fragment::Fragment;
+use crate::internals::attr;
+use crate::private;
+use quote::quote;
+
+/// Generates `Deserialize::deserialize` body for a `struct Unit;`
+pub fn deserialize_unit_struct(params: &Parameters, cattrs: &attr::Container) -> Fragment {
+    let this_type = &params.this_type;
+    let this_value = &params.this_value;
+    let type_name = cattrs.name().deserialize_name();
+    let (de_impl_generics, de_ty_generics, ty_generics, where_clause) = params.generics();
+    let delife = params.borrowed.de_lifetime();
+
+    let expecting = format!("unit struct {}", params.type_name());
+    let expecting = cattrs.expecting().unwrap_or(&expecting);
+
+    quote_block! {
+        #[doc(hidden)]
+        struct __Visitor #de_impl_generics #where_clause {
+            marker: _serde::#private::PhantomData<#this_type #ty_generics>,
+            lifetime: _serde::#private::PhantomData<&#delife ()>,
+        }
+
+        #[automatically_derived]
+        impl #de_impl_generics _serde::de::Visitor<#delife> for __Visitor #de_ty_generics #where_clause {
+            type Value = #this_type #ty_generics;
+
+            fn expecting(&self, __formatter: &mut _serde::#private::Formatter) -> _serde::#private::fmt::Result {
+                _serde::#private::Formatter::write_str(__formatter, #expecting)
+            }
+
+            #[inline]
+            fn visit_unit<__E>(self) -> _serde::#private::Result<Self::Value, __E>
+            where
+                __E: _serde::de::Error,
+            {
+                _serde::#private::Ok(#this_value)
+            }
+        }
+
+        _serde::Deserializer::deserialize_unit_struct(
+            __deserializer,
+            #type_name,
+            __Visitor {
+                marker: _serde::#private::PhantomData::<#this_type #ty_generics>,
+                lifetime: _serde::#private::PhantomData,
+            },
+        )
+    }
+}