Impls of ToSql for different generic types (Box, Cow, Rc, Arc). (#660)

* Impl ToSql for Box<str>

* Add generic impls for Cow, Box, Rc, Arc. Remove impl for Box<str>

* Remove impl of ToSql for Cow<'_, str>

* Add missing as_ref

Co-authored-by: Øsystems <>

src/types/to_sql.rs

@@ -94,6 +94,33 @@ impl ToSql for Box<dyn ToSql> {
     }
 }
 
+impl<T: ToSql + Clone> ToSql for Cow<'_, T> {
+    fn to_sql(&self) -> Result<ToSqlOutput<'_>> {
+        self.as_ref().to_sql()
+    }
+}
+
+impl<T: ToSql> ToSql for Box<T> {
+    fn to_sql(&self) -> Result<ToSqlOutput<'_>> {
+        let derefed: &dyn ToSql = &**self;
+        derefed.to_sql()
+    }
+}
+
+impl<T: ToSql> ToSql for std::rc::Rc<T> {
+    fn to_sql(&self) -> Result<ToSqlOutput<'_>> {
+        let derefed: &dyn ToSql = &**self;
+        derefed.to_sql()
+    }
+}
+
+impl<T: ToSql> ToSql for std::sync::Arc<T> {
+    fn to_sql(&self) -> Result<ToSqlOutput<'_>> {
+        let derefed: &dyn ToSql = &**self;
+        derefed.to_sql()
+    }
+}
+
 // We should be able to use a generic impl like this:
 //
 // impl<T: Copy> ToSql for T where T: Into<Value> {
@@ -182,12 +209,6 @@ impl<T: ToSql> ToSql for Option<T> {
     }
 }
 
-impl ToSql for Cow<'_, str> {
-    fn to_sql(&self) -> Result<ToSqlOutput<'_>> {
-        Ok(ToSqlOutput::from(self.as_ref()))
-    }
-}
-
 #[cfg(test)]
 mod test {
     use super::ToSql;
@@ -217,6 +238,29 @@ mod test {
         assert!(r.is_ok());
     }
 
+    #[test]
+    fn test_box() {
+        let s: Box<str> = "Hello world!".into();
+        let r = s.to_sql();
+
+        assert!(r.is_ok());
+    }
+
+    #[test]
+    fn test_cells() {
+        use std::{rc::Rc, sync::Arc};
+
+        let source_str: Box<str> = "Hello world!".into();
+
+        let s: Rc<_> = Rc::new(source_str.clone());
+        let r = s.to_sql();
+        assert!(r.is_ok());
+
+        let s: Arc<_> = Arc::new(source_str);
+        let r = s.to_sql();
+        assert!(r.is_ok());
+    }
+
     #[cfg(feature = "i128_blob")]
     #[test]
     fn test_i128() {