From 6b3777b6170bf6ead1cbc60ad108f0a2588fba2e Mon Sep 17 00:00:00 2001
From: David Tolnay <dtolnay@gmail.com>
Date: Sat, 20 Jun 2020 19:02:26 -0700
Subject: [PATCH] Remove len hint specialization

---
 serde/src/lib.rs     |  2 +-
 serde/src/ser/mod.rs | 33 ++-------------------------------
 2 files changed, 3 insertions(+), 32 deletions(-)

diff --git a/serde/src/lib.rs b/serde/src/lib.rs
index c43ba6e4..f2aec304 100644
--- a/serde/src/lib.rs
+++ b/serde/src/lib.rs
@@ -89,7 +89,7 @@
 // discussion of these features please refer to this issue:
 //
 //    https://github.com/serde-rs/serde/issues/812
-#![cfg_attr(feature = "unstable", feature(specialization, never_type))]
+#![cfg_attr(feature = "unstable", feature(never_type))]
 #![allow(unknown_lints, bare_trait_objects, deprecated)]
 #![cfg_attr(feature = "cargo-clippy", allow(renamed_and_removed_lints))]
 #![cfg_attr(feature = "cargo-clippy", deny(clippy, clippy_pedantic))]
diff --git a/serde/src/ser/mod.rs b/serde/src/ser/mod.rs
index 8b57c026..676b0e2f 100644
--- a/serde/src/ser/mod.rs
+++ b/serde/src/ser/mod.rs
@@ -1278,7 +1278,7 @@ pub trait Serializer: Sized {
         <I as IntoIterator>::Item: Serialize,
     {
         let iter = iter.into_iter();
-        let mut serializer = try!(self.serialize_seq(iter.len_hint()));
+        let mut serializer = try!(self.serialize_seq(iterator_len_hint(&iter)));
         for item in iter {
             try!(serializer.serialize_element(&item));
         }
@@ -1318,7 +1318,7 @@ pub trait Serializer: Sized {
         I: IntoIterator<Item = (K, V)>,
     {
         let iter = iter.into_iter();
-        let mut serializer = try!(self.serialize_map(iter.len_hint()));
+        let mut serializer = try!(self.serialize_map(iterator_len_hint(&iter)));
         for (key, value) in iter {
             try!(serializer.serialize_entry(&key, &value));
         }
@@ -1953,35 +1953,6 @@ pub trait SerializeStructVariant {
     fn end(self) -> Result<Self::Ok, Self::Error>;
 }
 
-trait LenHint: Iterator {
-    fn len_hint(&self) -> Option<usize>;
-}
-
-impl<I> LenHint for I
-where
-    I: Iterator,
-{
-    #[cfg(not(feature = "unstable"))]
-    fn len_hint(&self) -> Option<usize> {
-        iterator_len_hint(self)
-    }
-
-    #[cfg(feature = "unstable")]
-    default fn len_hint(&self) -> Option<usize> {
-        iterator_len_hint(self)
-    }
-}
-
-#[cfg(feature = "unstable")]
-impl<I> LenHint for I
-where
-    I: ExactSizeIterator,
-{
-    fn len_hint(&self) -> Option<usize> {
-        Some(self.len())
-    }
-}
-
 fn iterator_len_hint<I>(iter: &I) -> Option<usize>
 where
     I: Iterator,