Touch up PR 814

src/lib.rs

@@ -379,7 +379,7 @@ mod lib {
     pub use self::core::convert::{self, From, Into};
     pub use self::core::default::{self, Default};
     pub use self::core::fmt::{self, Debug, Display};
-    pub use self::core::hash::{self, Hash};
+    pub use self::core::hash::{self, Hash, Hasher};
     pub use self::core::iter::FusedIterator;
     pub use self::core::marker::{self, PhantomData};
     pub use self::core::ops::{Bound, RangeBounds};

src/number.rs

@@ -48,17 +48,16 @@ impl PartialEq for N {
 impl Eq for N {}
 
 #[cfg(not(feature = "arbitrary_precision"))]
-impl core::hash::Hash for N {
-    fn hash<H: core::hash::Hasher>(&self, h: &mut H) {
-        match self {
+impl Hash for N {
+    fn hash<H: Hasher>(&self, h: &mut H) {
+        match *self {
             N::PosInt(i) => i.hash(h),
             N::NegInt(i) => i.hash(h),
             N::Float(f) => {
-                // Using `f64::to_bits` here is fine since any float values are never `NaN`.
-                if *f == 0.0f64 {
-                    // The IEEE 754 standard has two representations for zero, +0 and -0,
-                    // such that +0 == -0.
-                    // In both cases we use the +0 hash so that hash(+0) == hash(-0).
+                if f == 0.0f64 {
+                    // There are 2 zero representations, +0 and -0, which
+                    // compare equal but have different bits. We use the +0 hash
+                    // for both so that hash(+0) == hash(-0).
                     0.0f64.to_bits().hash(h);
                 } else {
                     f.to_bits().hash(h);

tests/test.rs

@@ -27,8 +27,10 @@ use serde_json::{
     from_reader, from_slice, from_str, from_value, json, to_string, to_string_pretty, to_value,
     to_vec, to_writer, Deserializer, Number, Value,
 };
+use std::collections::hash_map::DefaultHasher;
 use std::collections::BTreeMap;
 use std::fmt::{self, Debug};
+use std::hash::{Hash, Hasher};
 use std::io;
 use std::iter;
 use std::marker::PhantomData;
@@ -2287,9 +2289,6 @@ fn test_value_into_deserializer() {
 
 #[test]
 fn hash_positive_and_negative_zero() {
-    use std::collections::hash_map::DefaultHasher;
-    use std::hash::{Hash, Hasher};
-
     fn hash(obj: impl Hash) -> u64 {
         let mut hasher = DefaultHasher::new();
         obj.hash(&mut hasher);
@@ -2298,5 +2297,11 @@ fn hash_positive_and_negative_zero() {
 
     let k1 = serde_json::from_str::<Number>("0.0").unwrap();
     let k2 = serde_json::from_str::<Number>("-0.0").unwrap();
-    assert!(k1 != k2 || hash(k1) == hash(k2));
+    if cfg!(feature = "arbitrary_precision") {
+        assert_ne!(k1, k2);
+        assert_ne!(hash(k1), hash(k2));
+    } else {
+        assert_eq!(k1, k2);
+        assert_eq!(hash(k1), hash(k2));
+    }
 }