Add a missing ToSql impl for postgres ranges

For some reasons the range implementation was missing the
`ToSql<Nullable<ST>> for T` impl.

Author: Eijebong

diesel/src/pg/types/ranges.rs

@@ -181,6 +181,20 @@ where
     }
 }
 
+
+impl<ST, T> ToSql<Nullable<Range<ST>>, Pg> for (Bound<T>, Bound<T>)
+where
+    Pg: HasSqlType<Range<ST>>,
+    (Bound<T>, Bound<T>): ToSql<Range<ST>, Pg>
+{
+    fn to_sql<W: Write>(
+        &self,
+        out: &mut ToSqlOutput<W, Pg>,
+    ) -> Result<IsNull, Box<Error + Send + Sync>> {
+        ToSql::<Range<ST>, Pg>::to_sql(self, out)
+    }
+}
+
 primitive_impls!(Int4range -> (pg: (3904, 3905)));
 primitive_impls!(Numrange -> (pg: (3906, 3907)));
 primitive_impls!(Tsrange -> (pg: (3908, 3909)));

diesel_tests/tests/types.rs

@@ -1122,3 +1122,38 @@ fn test_range_to_sql() {
         (Bound<i32>, Bound<i32>),
     >(expected_value, value));
 }
+
+#[cfg(feature = "postgres")]
+#[test]
+fn test_inserting_ranges() {
+    use std::collections::Bound;
+
+    let connection = connection();
+    connection
+        .execute(
+            "CREATE TABLE has_ranges (
+                        id SERIAL PRIMARY KEY,
+                        nul_range INT4RANGE,
+                        range INT4RANGE NOT NULL)",
+        )
+        .unwrap();
+    table!(
+        has_ranges(id) {
+            id -> Int4,
+            nul_range -> Nullable<Range<Int4>>,
+            range -> Range<Int4>,
+        }
+    );
+
+    let value = (Bound::Included(1), Bound::Excluded(3));
+
+    let (_, v1, v2): (i32, Option<(_, _)>, (_, _)) = insert_into(has_ranges::table)
+        .values((
+            has_ranges::nul_range.eq(value),
+            has_ranges::range.eq(value),
+        ))
+        .get_result(&connection)
+        .unwrap();
+    assert_eq!(v1, Some(value));
+    assert_eq!(v2, value);
+}