From 7a6e4bfeb79fee75f8616ca3a01e592206d18979 Mon Sep 17 00:00:00 2001
From: David Tolnay <dtolnay@gmail.com>
Date: Thu, 9 Feb 2017 11:07:04 -0800
Subject: [PATCH] Expose serde_json::de::Read to use in where clauses

---
 json/src/de.rs   | 28 +++++++++++++++++++++++-----
 json/src/read.rs | 23 ++++++++++++++++++++++-
 2 files changed, 45 insertions(+), 6 deletions(-)

diff --git a/json/src/de.rs b/json/src/de.rs
index 5d930594a..562821fa1 100644
--- a/json/src/de.rs
+++ b/json/src/de.rs
@@ -8,7 +8,9 @@ use serde::de::{self, Unexpected};
 
 use super::error::{Error, ErrorCode, Result};
 
-use read::{self, Read};
+use read;
+
+pub use read::Read;
 
 //////////////////////////////////////////////////////////////////////////////
 
@@ -873,10 +875,26 @@ impl<'a, R: Read + 'a> de::VariantVisitor for UnitVariantVisitor<'a, R> {
 //////////////////////////////////////////////////////////////////////////////
 
 /// Iterator that deserializes a stream into multiple JSON values.
-pub struct StreamDeserializer<R, T>
-    where R: Read,
-          T: de::Deserialize,
-{
+///
+/// A stream deserializer can be create from any JSON deserializer using the
+/// `Deserializer::into_iter` method.
+///
+/// ```rust
+/// extern crate serde_json;
+///
+/// use serde_json::{Deserializer, Value};
+///
+/// fn main() {
+///     let data = "1 2 {\"k\": 3}";
+///
+///     let stream = Deserializer::from_str(data).into_iter::<Value>();
+///
+///     for value in stream {
+///         println!("{}", value.unwrap());
+///     }
+/// }
+/// ```
+pub struct StreamDeserializer<R, T> {
     de: Deserializer<R>,
     _marker: PhantomData<T>,
 }
diff --git a/json/src/read.rs b/json/src/read.rs
index d00cb2b06..364e14b7a 100644
--- a/json/src/read.rs
+++ b/json/src/read.rs
@@ -7,11 +7,17 @@ use super::error::{Error, ErrorCode, Result};
 /// Trait used by the deserializer for iterating over input. This is manually
 /// "specialized" for iterating over &[u8]. Once feature(specialization) is
 /// stable we can use actual specialization.
-pub trait Read {
+///
+/// This trait is sealed and cannot be implemented for types outside of
+/// `serde_json`.
+pub trait Read: private::Sealed {
+    #[doc(hidden)]
     fn next(&mut self) -> io::Result<Option<u8>>;
+    #[doc(hidden)]
     fn peek(&mut self) -> io::Result<Option<u8>>;
 
     /// Only valid after a call to peek(). Discards the peeked byte.
+    #[doc(hidden)]
     fn discard(&mut self);
 
     /// Position of the most recent call to next().
@@ -21,6 +27,7 @@ pub trait Read {
     /// actually peek() because we don't always know.
     ///
     /// Only called in case of an error, so performance is not important.
+    #[doc(hidden)]
     fn position(&self) -> Position;
 
     /// Position of the most recent call to peek().
@@ -30,11 +37,13 @@ pub trait Read {
     /// actually next() because we don't always know.
     ///
     /// Only called in case of an error, so performance is not important.
+    #[doc(hidden)]
     fn peek_position(&self) -> Position;
 
     /// Assumes the previous byte was a quotation mark. Parses a JSON-escaped
     /// string until the next quotation mark using the given scratch space if
     /// necessary. The scratch space is initially empty.
+    #[doc(hidden)]
     fn parse_str<'s>(
         &'s mut self,
         scratch: &'s mut Vec<u8>
@@ -68,6 +77,11 @@ pub struct StrRead<'a> {
     delegate: SliceRead<'a>,
 }
 
+// Prevent users from implementing the Read trait.
+mod private {
+    pub trait Sealed {}
+}
+
 //////////////////////////////////////////////////////////////////////////////
 
 impl<Iter> IteratorRead<Iter>
@@ -81,6 +95,9 @@ impl<Iter> IteratorRead<Iter>
     }
 }
 
+impl<Iter> private::Sealed for IteratorRead<Iter>
+    where Iter: Iterator<Item = io::Result<u8>> {}
+
 impl<Iter> Read for IteratorRead<Iter>
     where Iter: Iterator<Item = io::Result<u8>>,
 {
@@ -242,6 +259,8 @@ impl<'a> SliceRead<'a> {
     }
 }
 
+impl<'a> private::Sealed for SliceRead<'a> {}
+
 impl<'a> Read for SliceRead<'a> {
     #[inline]
     fn next(&mut self) -> io::Result<Option<u8>> {
@@ -300,6 +319,8 @@ impl<'a> StrRead<'a> {
     }
 }
 
+impl<'a> private::Sealed for StrRead<'a> {}
+
 impl<'a> Read for StrRead<'a> {
     #[inline]
     fn next(&mut self) -> io::Result<Option<u8>> {