Fix adjacently tagged f32 roundtrip regression

Cargo.toml

@@ -22,6 +22,7 @@ itoa = "0.4.3"
 ryu = "0.2"
 
 [dev-dependencies]
+automod = "0.1"
 compiletest_rs = { version = "0.3", features = ["stable"] }
 serde_bytes = "0.10"
 serde_derive = "1.0"

src/number.rs

@@ -473,7 +473,7 @@ macro_rules! deserialize_any {
             } else if let Some(i) = self.as_i64() {
                 return visitor.visit_i64(i);
             } else if let Some(f) = self.as_f64() {
-                if f.to_string() == self.n {
+                if ryu::Buffer::new().format(f) == self.n || f.to_string() == self.n {
                     return visitor.visit_f64(f);
                 }
             }

tests/regression.rs

@@ -0,0 +1,6 @@
+extern crate automod;
+extern crate serde;
+extern crate serde_derive;
+
+#[path = "regression/mod.rs"]
+mod regression;

tests/regression/issue520.rs

@@ -0,0 +1,18 @@
+use serde_derive::{Serialize, Deserialize};
+
+#[derive(Serialize, Deserialize, Debug)]
+#[serde(tag = "type", content = "data")]
+enum E {
+    Float(f32),
+}
+
+#[test]
+fn test() {
+    let e = E::Float(159.1);
+    let v = serde_json::to_value(e).unwrap();
+    let e = serde_json::from_value::<E>(v).unwrap();
+
+    match e {
+        E::Float(f) => assert_eq!(f, 159.1),
+    }
+}

tests/regression/mod.rs

@@ -0,0 +1 @@
+automod::dir!("tests/regression");