Adds explicit serialization for f32 to avoid rounding artifacts when …

…promoting f32 to f64

src/ser.rs

@@ -514,7 +514,16 @@ impl ser::Serializer for SerializerToYaml {
     }
 
     fn serialize_f32(self, v: f32) -> Result<Yaml> {
-        self.serialize_f64(v as f64)
+        Ok(Yaml::Real(match v.classify() {
+            num::FpCategory::Infinite if v.is_sign_positive() => ".inf".into(),
+            num::FpCategory::Infinite => "-.inf".into(),
+            num::FpCategory::Nan => ".nan".into(),
+            _ => {
+                let mut buf = vec![];
+                ::dtoa::write(&mut buf, v).unwrap();
+                ::std::str::from_utf8(&buf).unwrap().into()
+            }
+        }))
     }
 
     fn serialize_f64(self, v: f64) -> Result<Yaml> {

tests/test_serde.rs

@@ -135,6 +135,16 @@ fn test_float() {
     assert!(float.is_nan());
 }
 
+#[test]
+fn test_float32() {
+    let thing: f32 = 25.6;
+    let yaml = indoc! {"
+        ---
+        25.6
+    "};
+    test_serde(&thing, yaml);
+}
+
 #[test]
 fn test_vec() {
     let thing = vec![1, 2, 3];