Relocate private size_hint module

Let's keep crate::__private for only things that *need* to be accessible
to the macro-generated code. Size_hint can be pub(crate).

serde/src/de/impls.rs

@@ -8,7 +8,7 @@ use crate::de::{
 use crate::seed::InPlaceSeed;
 
 #[cfg(any(feature = "std", feature = "alloc"))]
-use crate::__private::size_hint;
+use crate::de::size_hint;
 
 ////////////////////////////////////////////////////////////////////////////////
 

serde/src/de/mod.rs

@@ -122,6 +122,7 @@ pub mod value;
 mod format;
 mod ignored_any;
 mod impls;
+pub(crate) mod size_hint;
 mod utf8;
 
 pub use self::ignored_any::IgnoredAny;

serde/src/de/value.rs

@@ -24,8 +24,7 @@
 use crate::lib::*;
 
 use self::private::{First, Second};
-use crate::__private::size_hint;
-use crate::de::{self, Deserializer, Expected, IntoDeserializer, SeqAccess, Visitor};
+use crate::de::{self, size_hint, Deserializer, Expected, IntoDeserializer, SeqAccess, Visitor};
 use crate::ser;
 
 ////////////////////////////////////////////////////////////////////////////////

serde/src/private/de.rs

@@ -208,12 +208,11 @@ mod content {
 
     use crate::lib::*;
 
-    use crate::__private::size_hint;
     use crate::actually_private;
     use crate::de::value::{MapDeserializer, SeqDeserializer};
     use crate::de::{
-        self, Deserialize, DeserializeSeed, Deserializer, EnumAccess, Expected, IgnoredAny,
-        MapAccess, SeqAccess, Unexpected, Visitor,
+        self, size_hint, Deserialize, DeserializeSeed, Deserializer, EnumAccess, Expected,
+        IgnoredAny, MapAccess, SeqAccess, Unexpected, Visitor,
     };
 
     /// Used from generated code to buffer the contents of the Deserializer when

serde/src/private/mod.rs

@@ -3,8 +3,6 @@ pub mod de;
 #[cfg(not(no_serde_derive))]
 pub mod ser;
 
-pub mod size_hint;
-
 // FIXME: #[cfg(doctest)] once https://github.com/rust-lang/rust/issues/67295 is fixed.
 pub mod doc;