feat(spanner): implement ToValue for str

src/spanner/src/to_value.rs

@@ -65,20 +65,24 @@ impl ToValue for ProtoValue {
 
 impl ToValue for String {
     fn to_value(&self) -> Value {
-        Value(ProtoValue {
-            kind: Some(prost_types::value::Kind::StringValue(self.clone())),
-        })
+        <str as ToValue>::to_value(self)
     }
 }
 
-impl ToValue for &str {
+impl ToValue for str {
     fn to_value(&self) -> Value {
         Value(ProtoValue {
             kind: Some(prost_types::value::Kind::StringValue(self.to_string())),
         })
     }
 }
 
+impl ToValue for &str {
+    fn to_value(&self) -> Value {
+        <str as ToValue>::to_value(*self)
+    }
+}
+
 impl ToValue for i64 {
     fn to_value(&self) -> Value {
         Value(ProtoValue {
@@ -211,6 +215,22 @@ mod tests {
         assert_eq!(v.as_string(), "world");
     }
 
+    #[test]
+    fn test_to_value_str_trait_bound() {
+        fn bind_param<T: ToValue + ?Sized>(val: &T) -> Value {
+            val.to_value()
+        }
+
+        let v = bind_param("hello");
+        assert_eq!(v.kind(), Kind::String);
+        assert_eq!(v.as_string(), "hello");
+
+        let owned: String = "hello".to_string();
+        assert_eq!(bind_param(&owned), v);
+        let borrowed: &str = &owned;
+        assert_eq!(bind_param(&borrowed), v);
+    }
+
     #[test]
     fn test_to_value_int() {
         let v = 42i64.to_value();