Merge pull request #3979 from formlogic-kirk/alias_op_impls

Alias op impls

Author: weiznich

diesel/src/query_source/aliasing/aliased_field.rs

@@ -1,3 +1,5 @@
+use diesel_derives::DieselNumericOps;
+
 use super::{Alias, AliasSource};
 
 use crate::backend::Backend;
@@ -13,7 +15,7 @@ use crate::sql_types;
 
 use std::marker::PhantomData;
 
-#[derive(Debug, Clone, Copy)]
+#[derive(Debug, Clone, Copy, DieselNumericOps)]
 /// Represents an aliased field (column) within diesel's query builder
 ///
 /// See [`alias!`](crate::alias) for more details.

diesel_tests/tests/alias.rs

@@ -26,6 +26,25 @@ fn selecting_basic_data() {
     assert_eq!(expected_data, actual_data);
 }
 
+#[test]
+fn ops_with_aliases() {
+    // This test should fail to compile if the std::ops::{Add, Sub, ...} impls are missing for AliasedField.
+    let likes_alias = alias!(likes as likes_alias);
+    let pokes_alias = alias!(pokes as pokes_alias);
+
+    // Using pokes::poke_count and comment_id as they are columns of the same type
+    let _unaliased = likes::table
+        .inner_join(pokes::table.on(likes::user_id.eq(pokes::user_id)))
+        .select(pokes::poke_count + likes::comment_id);
+    let _aliased = likes_alias
+        .inner_join(
+            pokes_alias.on(likes_alias
+                .field(likes::user_id)
+                .eq(pokes_alias.field(pokes::user_id))),
+        )
+        .select(pokes_alias.field(pokes::poke_count) + likes_alias.field(likes::comment_id));
+}
+
 #[test]
 fn select_multiple_from_join() {
     let connection = &mut connection_with_sean_and_tess_in_users_table();