diff --git a/diesel_compile_tests/tests/fail/invalid_joins.rs b/diesel_compile_tests/tests/fail/invalid_joins.rs
new file mode 100644
index 000000000000..0ece4b0289ab
--- /dev/null
+++ b/diesel_compile_tests/tests/fail/invalid_joins.rs
@@ -0,0 +1,68 @@
+extern crate diesel;
+
+use diesel::*;
+
+table! {
+    users {
+        id -> Integer,
+        name -> VarChar,
+    }
+}
+
+table! {
+    posts {
+        id -> Integer,
+        title -> Text,
+        user_id -> Integer,
+    }
+}
+
+table! {
+    comments {
+        id -> Integer,
+        user_id -> Integer,
+        post_id -> Integer,
+        name -> Text,
+    }
+}
+
+joinable!(posts -> users (user_id));
+joinable!(comments -> users (user_id));
+joinable!(comments -> posts (post_id));
+allow_tables_to_appear_in_same_query!(posts, users, comments);
+
+fn main() {}
+
+fn invalid_inner_joins() {
+    // This is a valid join
+    let _ = users::table.inner_join(posts::table);
+
+    // This fails, because we join the same table more than once
+    let _ = users::table.inner_join(posts::table.inner_join(users::table));
+
+    // It also fails if we use an explicit on clause
+    let _ = users::table.inner_join(posts::table.inner_join(users::table.on(posts::user_id.eq(users::id))));
+
+    // Also if we put the on clause on the first join
+    let _ = users::table.inner_join(posts::table.on(users::id.eq(posts::user_id)).inner_join(users::table));
+
+    // it also fails if we join to another subjoin
+    let _ = users::table.inner_join(comments::table).inner_join(posts::table.inner_join(comments::table));
+}
+
+fn invalid_left_joins() {
+    // This is a valid join
+    let _ = users::table.left_join(posts::table);
+
+    // This fails, because we join the same table more than once
+    let _ = users::table.left_join(posts::table.left_join(users::table));
+
+    // It also fails if we use an explicit on clause
+    let _ = users::table.left_join(posts::table.left_join(users::table.on(posts::user_id.eq(users::id))));
+
+    // Also if we put the on clause on the first join
+    let _ = users::table.left_join(posts::table.on(users::id.eq(posts::user_id)).left_join(users::table));
+
+    // it also fails if we join to another subjoin
+    let _ = users::table.left_join(comments::table).left_join(posts::table.left_join(comments::table));
+}
diff --git a/diesel_compile_tests/tests/fail/invalid_joins.stderr b/diesel_compile_tests/tests/fail/invalid_joins.stderr
new file mode 100644
index 000000000000..97d7a562eed1
--- /dev/null
+++ b/diesel_compile_tests/tests/fail/invalid_joins.stderr
@@ -0,0 +1,493 @@
+error[E0271]: type mismatch resolving `<diesel::query_source::Once as Plus<diesel::query_source::Once>>::Output == diesel::query_source::Once`
+  --> tests/fail/invalid_joins.rs:41:26
+   |
+41 |     let _ = users::table.inner_join(posts::table.inner_join(users::table));
+   |                          ^^^^^^^^^^ expected struct `MoreThanOnce`, found struct `diesel::query_source::Once`
+   |
+note: required because of the requirements on the impl of `AppearsOnTable<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, Inner>>` for `users::columns::id`
+  --> tests/fail/invalid_joins.rs:5:1
+   |
+5  | / table! {
+6  | |     users {
+7  | |         id -> Integer,
+8  | |         name -> VarChar,
+9  | |     }
+10 | | }
+   | |_^
+   = note: 2 redundant requirements hidden
+   = note: required because of the requirements on the impl of `AppearsOnTable<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, Inner>>` for `((users::columns::id, users::columns::name), query_source::joins::private::SkipSelectableExpressionBoundCheckWrapper<((posts::columns::id, posts::columns::title, posts::columns::user_id), (users::columns::id, users::columns::name))>)`
+   = note: required because of the requirements on the impl of `QuerySource` for `query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, Inner>`
+   = note: 1 redundant requirement hidden
+   = note: required because of the requirements on the impl of `QuerySource` for `JoinOn<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>`
+   = note: required because of the requirements on the impl of `InternalJoinDsl<SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, Inner, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>` for `SelectStatement<FromClause<users::table>>`
+   = note: this error originates in the macro `$crate::__diesel_column` which comes from the expansion of the macro `table` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0271]: type mismatch resolving `<diesel::query_source::Once as Plus<diesel::query_source::Once>>::Output == diesel::query_source::Once`
+  --> tests/fail/invalid_joins.rs:41:37
+   |
+41 |     let _ = users::table.inner_join(posts::table.inner_join(users::table));
+   |                          ---------- ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected struct `MoreThanOnce`, found struct `diesel::query_source::Once`
+   |                          |
+   |                          required by a bound introduced by this call
+   |
+note: required because of the requirements on the impl of `AppearsOnTable<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, Inner>>` for `users::columns::id`
+  --> tests/fail/invalid_joins.rs:5:1
+   |
+5  | / table! {
+6  | |     users {
+7  | |         id -> Integer,
+8  | |         name -> VarChar,
+9  | |     }
+10 | | }
+   | |_^
+   = note: 2 redundant requirements hidden
+   = note: required because of the requirements on the impl of `AppearsOnTable<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, Inner>>` for `((users::columns::id, users::columns::name), query_source::joins::private::SkipSelectableExpressionBoundCheckWrapper<((posts::columns::id, posts::columns::title, posts::columns::user_id), (users::columns::id, users::columns::name))>)`
+   = note: required because of the requirements on the impl of `QuerySource` for `query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, Inner>`
+   = note: 1 redundant requirement hidden
+   = note: required because of the requirements on the impl of `QuerySource` for `JoinOn<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>`
+   = note: required because of the requirements on the impl of `InternalJoinDsl<SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, Inner, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>` for `SelectStatement<FromClause<users::table>>`
+   = note: 1 redundant requirement hidden
+   = note: required because of the requirements on the impl of `InternalJoinDsl<SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, Inner, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>` for `users::table`
+   = note: this error originates in the macro `$crate::__diesel_column` which comes from the expansion of the macro `table` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0271]: type mismatch resolving `<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, Inner> as AppearsInFromClause<users::table>>::Count == diesel::query_source::Once`
+  --> tests/fail/invalid_joins.rs:41:26
+   |
+41 |     let _ = users::table.inner_join(posts::table.inner_join(users::table));
+   |                          ^^^^^^^^^^ expected struct `MoreThanOnce`, found struct `diesel::query_source::Once`
+   |
+note: required because of the requirements on the impl of `AppearsOnTable<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, Inner>>` for `users::columns::id`
+  --> tests/fail/invalid_joins.rs:5:1
+   |
+5  | / table! {
+6  | |     users {
+7  | |         id -> Integer,
+8  | |         name -> VarChar,
+9  | |     }
+10 | | }
+   | |_^
+   = note: 3 redundant requirements hidden
+   = note: required because of the requirements on the impl of `AppearsOnTable<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, Inner>>` for `diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>`
+   = note: required because of the requirements on the impl of `QuerySource` for `JoinOn<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>`
+   = note: required because of the requirements on the impl of `InternalJoinDsl<SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, Inner, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>` for `SelectStatement<FromClause<users::table>>`
+   = note: this error originates in the macro `$crate::__diesel_column` which comes from the expansion of the macro `table` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0271]: type mismatch resolving `<diesel::query_source::Once as Plus<diesel::query_source::Once>>::Output == diesel::query_source::Once`
+  --> tests/fail/invalid_joins.rs:44:26
+   |
+44 |     let _ = users::table.inner_join(posts::table.inner_join(users::table.on(posts::user_id.eq(users::id))));
+   |                          ^^^^^^^^^^ expected struct `MoreThanOnce`, found struct `diesel::query_source::Once`
+   |
+note: required because of the requirements on the impl of `AppearsOnTable<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<posts::columns::user_id, users::columns::id>>>>>, Inner>>` for `users::columns::id`
+  --> tests/fail/invalid_joins.rs:5:1
+   |
+5  | / table! {
+6  | |     users {
+7  | |         id -> Integer,
+8  | |         name -> VarChar,
+9  | |     }
+10 | | }
+   | |_^
+   = note: 2 redundant requirements hidden
+   = note: required because of the requirements on the impl of `AppearsOnTable<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<posts::columns::user_id, users::columns::id>>>>>, Inner>>` for `((users::columns::id, users::columns::name), query_source::joins::private::SkipSelectableExpressionBoundCheckWrapper<((posts::columns::id, posts::columns::title, posts::columns::user_id), (users::columns::id, users::columns::name))>)`
+   = note: required because of the requirements on the impl of `QuerySource` for `query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<posts::columns::user_id, users::columns::id>>>>>, Inner>`
+   = note: 1 redundant requirement hidden
+   = note: required because of the requirements on the impl of `QuerySource` for `JoinOn<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<posts::columns::user_id, users::columns::id>>>>>, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>`
+   = note: required because of the requirements on the impl of `InternalJoinDsl<SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<posts::columns::user_id, users::columns::id>>>>>, Inner, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>` for `SelectStatement<FromClause<users::table>>`
+   = note: this error originates in the macro `$crate::__diesel_column` which comes from the expansion of the macro `table` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0271]: type mismatch resolving `<diesel::query_source::Once as Plus<diesel::query_source::Once>>::Output == diesel::query_source::Once`
+  --> tests/fail/invalid_joins.rs:44:37
+   |
+44 |     let _ = users::table.inner_join(posts::table.inner_join(users::table.on(posts::user_id.eq(users::id))));
+   |                          ---------- ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected struct `MoreThanOnce`, found struct `diesel::query_source::Once`
+   |                          |
+   |                          required by a bound introduced by this call
+   |
+note: required because of the requirements on the impl of `AppearsOnTable<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<posts::columns::user_id, users::columns::id>>>>>, Inner>>` for `users::columns::id`
+  --> tests/fail/invalid_joins.rs:5:1
+   |
+5  | / table! {
+6  | |     users {
+7  | |         id -> Integer,
+8  | |         name -> VarChar,
+9  | |     }
+10 | | }
+   | |_^
+   = note: 2 redundant requirements hidden
+   = note: required because of the requirements on the impl of `AppearsOnTable<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<posts::columns::user_id, users::columns::id>>>>>, Inner>>` for `((users::columns::id, users::columns::name), query_source::joins::private::SkipSelectableExpressionBoundCheckWrapper<((posts::columns::id, posts::columns::title, posts::columns::user_id), (users::columns::id, users::columns::name))>)`
+   = note: required because of the requirements on the impl of `QuerySource` for `query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<posts::columns::user_id, users::columns::id>>>>>, Inner>`
+   = note: 1 redundant requirement hidden
+   = note: required because of the requirements on the impl of `QuerySource` for `JoinOn<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<posts::columns::user_id, users::columns::id>>>>>, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>`
+   = note: required because of the requirements on the impl of `InternalJoinDsl<SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<posts::columns::user_id, users::columns::id>>>>>, Inner, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>` for `SelectStatement<FromClause<users::table>>`
+   = note: 1 redundant requirement hidden
+   = note: required because of the requirements on the impl of `InternalJoinDsl<SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<posts::columns::user_id, users::columns::id>>>>>, Inner, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>` for `users::table`
+   = note: this error originates in the macro `$crate::__diesel_column` which comes from the expansion of the macro `table` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0271]: type mismatch resolving `<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<posts::columns::user_id, users::columns::id>>>>>, Inner> as AppearsInFromClause<users::table>>::Count == diesel::query_source::Once`
+  --> tests/fail/invalid_joins.rs:44:26
+   |
+44 |     let _ = users::table.inner_join(posts::table.inner_join(users::table.on(posts::user_id.eq(users::id))));
+   |                          ^^^^^^^^^^ expected struct `MoreThanOnce`, found struct `diesel::query_source::Once`
+   |
+note: required because of the requirements on the impl of `AppearsOnTable<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<posts::columns::user_id, users::columns::id>>>>>, Inner>>` for `users::columns::id`
+  --> tests/fail/invalid_joins.rs:5:1
+   |
+5  | / table! {
+6  | |     users {
+7  | |         id -> Integer,
+8  | |         name -> VarChar,
+9  | |     }
+10 | | }
+   | |_^
+   = note: 3 redundant requirements hidden
+   = note: required because of the requirements on the impl of `AppearsOnTable<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<posts::columns::user_id, users::columns::id>>>>>, Inner>>` for `diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>`
+   = note: required because of the requirements on the impl of `QuerySource` for `JoinOn<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<posts::columns::user_id, users::columns::id>>>>>, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>`
+   = note: required because of the requirements on the impl of `InternalJoinDsl<SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<posts::columns::user_id, users::columns::id>>>>>, Inner, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>` for `SelectStatement<FromClause<users::table>>`
+   = note: this error originates in the macro `$crate::__diesel_column` which comes from the expansion of the macro `table` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0271]: type mismatch resolving `<diesel::query_source::Once as Plus<diesel::query_source::Once>>::Output == diesel::query_source::Once`
+  --> tests/fail/invalid_joins.rs:47:26
+   |
+47 |     let _ = users::table.inner_join(posts::table.on(users::id.eq(posts::user_id)).inner_join(users::table));
+   |                          ^^^^^^^^^^ expected struct `MoreThanOnce`, found struct `diesel::query_source::Once`
+   |
+note: required because of the requirements on the impl of `AppearsOnTable<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, Inner>>` for `users::columns::id`
+  --> tests/fail/invalid_joins.rs:5:1
+   |
+5  | / table! {
+6  | |     users {
+7  | |         id -> Integer,
+8  | |         name -> VarChar,
+9  | |     }
+10 | | }
+   | |_^
+   = note: 2 redundant requirements hidden
+   = note: required because of the requirements on the impl of `AppearsOnTable<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, Inner>>` for `((users::columns::id, users::columns::name), query_source::joins::private::SkipSelectableExpressionBoundCheckWrapper<((posts::columns::id, posts::columns::title, posts::columns::user_id), (users::columns::id, users::columns::name))>)`
+   = note: required because of the requirements on the impl of `QuerySource` for `query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, Inner>`
+   = note: 1 redundant requirement hidden
+   = note: required because of the requirements on the impl of `QuerySource` for `JoinOn<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<users::columns::id, posts::columns::user_id>>>`
+   = note: required because of the requirements on the impl of `InternalJoinDsl<SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, Inner, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<users::columns::id, posts::columns::user_id>>>` for `SelectStatement<FromClause<users::table>>`
+   = note: this error originates in the macro `$crate::__diesel_column` which comes from the expansion of the macro `table` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0271]: type mismatch resolving `<diesel::query_source::Once as Plus<diesel::query_source::Once>>::Output == diesel::query_source::Once`
+  --> tests/fail/invalid_joins.rs:47:37
+   |
+47 |     let _ = users::table.inner_join(posts::table.on(users::id.eq(posts::user_id)).inner_join(users::table));
+   |                          ---------- ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected struct `MoreThanOnce`, found struct `diesel::query_source::Once`
+   |                          |
+   |                          required by a bound introduced by this call
+   |
+note: required because of the requirements on the impl of `AppearsOnTable<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, Inner>>` for `users::columns::id`
+  --> tests/fail/invalid_joins.rs:5:1
+   |
+5  | / table! {
+6  | |     users {
+7  | |         id -> Integer,
+8  | |         name -> VarChar,
+9  | |     }
+10 | | }
+   | |_^
+   = note: 2 redundant requirements hidden
+   = note: required because of the requirements on the impl of `AppearsOnTable<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, Inner>>` for `((users::columns::id, users::columns::name), query_source::joins::private::SkipSelectableExpressionBoundCheckWrapper<((posts::columns::id, posts::columns::title, posts::columns::user_id), (users::columns::id, users::columns::name))>)`
+   = note: required because of the requirements on the impl of `QuerySource` for `query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, Inner>`
+   = note: 1 redundant requirement hidden
+   = note: required because of the requirements on the impl of `QuerySource` for `JoinOn<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<users::columns::id, posts::columns::user_id>>>`
+   = note: required because of the requirements on the impl of `InternalJoinDsl<SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, Inner, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<users::columns::id, posts::columns::user_id>>>` for `SelectStatement<FromClause<users::table>>`
+   = note: 1 redundant requirement hidden
+   = note: required because of the requirements on the impl of `InternalJoinDsl<SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, Inner, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<users::columns::id, posts::columns::user_id>>>` for `users::table`
+   = note: this error originates in the macro `$crate::__diesel_column` which comes from the expansion of the macro `table` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0271]: type mismatch resolving `<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, Inner> as AppearsInFromClause<users::table>>::Count == diesel::query_source::Once`
+  --> tests/fail/invalid_joins.rs:47:26
+   |
+47 |     let _ = users::table.inner_join(posts::table.on(users::id.eq(posts::user_id)).inner_join(users::table));
+   |                          ^^^^^^^^^^ expected struct `MoreThanOnce`, found struct `diesel::query_source::Once`
+   |
+note: required because of the requirements on the impl of `AppearsOnTable<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, Inner>>` for `users::columns::id`
+  --> tests/fail/invalid_joins.rs:5:1
+   |
+5  | / table! {
+6  | |     users {
+7  | |         id -> Integer,
+8  | |         name -> VarChar,
+9  | |     }
+10 | | }
+   | |_^
+   = note: 2 redundant requirements hidden
+   = note: required because of the requirements on the impl of `AppearsOnTable<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, Inner>>` for `diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<users::columns::id, posts::columns::user_id>>`
+   = note: required because of the requirements on the impl of `QuerySource` for `JoinOn<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<users::columns::id, posts::columns::user_id>>>`
+   = note: required because of the requirements on the impl of `InternalJoinDsl<SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, Inner, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<users::columns::id, posts::columns::user_id>>>` for `SelectStatement<FromClause<users::table>>`
+   = note: this error originates in the macro `$crate::__diesel_column` which comes from the expansion of the macro `table` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0271]: type mismatch resolving `<diesel::query_source::Once as Plus<diesel::query_source::Once>>::Output == diesel::query_source::Once`
+  --> tests/fail/invalid_joins.rs:50:54
+   |
+50 |     let _ = users::table.inner_join(comments::table).inner_join(posts::table.inner_join(comments::table));
+   |                                                      ^^^^^^^^^^ expected struct `MoreThanOnce`, found struct `diesel::query_source::Once`
+   |
+note: required because of the requirements on the impl of `AppearsOnTable<query_source::joins::Join<JoinOn<query_source::joins::Join<users::table, comments::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<comments::columns::user_id>, NullableExpression<users::columns::id>>>>, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, comments::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<comments::columns::post_id>, NullableExpression<posts::columns::id>>>>>>, Inner>>` for `comments::columns::id`
+  --> tests/fail/invalid_joins.rs:20:1
+   |
+20 | / table! {
+21 | |     comments {
+22 | |         id -> Integer,
+23 | |         user_id -> Integer,
+...  |
+26 | |     }
+27 | | }
+   | |_^
+   = note: 2 redundant requirements hidden
+   = note: required because of the requirements on the impl of `AppearsOnTable<query_source::joins::Join<JoinOn<query_source::joins::Join<users::table, comments::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<comments::columns::user_id>, NullableExpression<users::columns::id>>>>, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, comments::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<comments::columns::post_id>, NullableExpression<posts::columns::id>>>>>>, Inner>>` for `((users::columns::id, users::columns::name), (comments::columns::id, comments::columns::user_id, comments::columns::post_id, comments::columns::name), query_source::joins::private::SkipSelectableExpressionBoundCheckWrapper<((posts::columns::id, posts::columns::title, posts::columns::user_id), (comments::columns::id, comments::columns::user_id, comments::columns::post_id, comments::columns::name))>)`
+   = note: required because of the requirements on the impl of `QuerySource` for `query_source::joins::Join<JoinOn<query_source::joins::Join<users::table, comments::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<comments::columns::user_id>, NullableExpression<users::columns::id>>>>, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, comments::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<comments::columns::post_id>, NullableExpression<posts::columns::id>>>>>>, Inner>`
+   = note: 1 redundant requirement hidden
+   = note: required because of the requirements on the impl of `QuerySource` for `JoinOn<query_source::joins::Join<JoinOn<query_source::joins::Join<users::table, comments::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<comments::columns::user_id>, NullableExpression<users::columns::id>>>>, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, comments::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<comments::columns::post_id>, NullableExpression<posts::columns::id>>>>>>, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>`
+   = note: required because of the requirements on the impl of `InternalJoinDsl<SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, comments::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<comments::columns::post_id>, NullableExpression<posts::columns::id>>>>>>, Inner, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>` for `SelectStatement<FromClause<JoinOn<query_source::joins::Join<users::table, comments::table, Inner>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<comments::columns::user_id>, NullableExpression<users::columns::id>>>>>>`
+   = note: this error originates in the macro `$crate::__diesel_column` which comes from the expansion of the macro `table` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0271]: type mismatch resolving `<diesel::query_source::Once as Plus<diesel::query_source::Once>>::Output == diesel::query_source::Once`
+  --> tests/fail/invalid_joins.rs:58:26
+   |
+58 |     let _ = users::table.left_join(posts::table.left_join(users::table));
+   |                          ^^^^^^^^^ expected struct `MoreThanOnce`, found struct `diesel::query_source::Once`
+   |
+note: required because of the requirements on the impl of `AppearsOnTable<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, LeftOuter>>` for `users::columns::id`
+  --> tests/fail/invalid_joins.rs:5:1
+   |
+5  | / table! {
+6  | |     users {
+7  | |         id -> Integer,
+8  | |         name -> VarChar,
+9  | |     }
+10 | | }
+   | |_^
+   = note: 2 redundant requirements hidden
+   = note: required because of the requirements on the impl of `AppearsOnTable<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, LeftOuter>>` for `((users::columns::id, users::columns::name), NullableExpression<query_source::joins::private::SkipSelectableExpressionBoundCheckWrapper<((posts::columns::id, posts::columns::title, posts::columns::user_id), NullableExpression<(users::columns::id, users::columns::name)>)>>)`
+   = note: required because of the requirements on the impl of `QuerySource` for `query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, LeftOuter>`
+   = note: 1 redundant requirement hidden
+   = note: required because of the requirements on the impl of `QuerySource` for `JoinOn<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>`
+   = note: required because of the requirements on the impl of `InternalJoinDsl<SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, LeftOuter, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>` for `SelectStatement<FromClause<users::table>>`
+   = note: this error originates in the macro `$crate::__diesel_column` which comes from the expansion of the macro `table` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0271]: type mismatch resolving `<diesel::query_source::Once as Plus<diesel::query_source::Once>>::Output == diesel::query_source::Once`
+  --> tests/fail/invalid_joins.rs:58:36
+   |
+58 |     let _ = users::table.left_join(posts::table.left_join(users::table));
+   |                          --------- ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected struct `MoreThanOnce`, found struct `diesel::query_source::Once`
+   |                          |
+   |                          required by a bound introduced by this call
+   |
+note: required because of the requirements on the impl of `AppearsOnTable<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, LeftOuter>>` for `users::columns::id`
+  --> tests/fail/invalid_joins.rs:5:1
+   |
+5  | / table! {
+6  | |     users {
+7  | |         id -> Integer,
+8  | |         name -> VarChar,
+9  | |     }
+10 | | }
+   | |_^
+   = note: 2 redundant requirements hidden
+   = note: required because of the requirements on the impl of `AppearsOnTable<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, LeftOuter>>` for `((users::columns::id, users::columns::name), NullableExpression<query_source::joins::private::SkipSelectableExpressionBoundCheckWrapper<((posts::columns::id, posts::columns::title, posts::columns::user_id), NullableExpression<(users::columns::id, users::columns::name)>)>>)`
+   = note: required because of the requirements on the impl of `QuerySource` for `query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, LeftOuter>`
+   = note: 1 redundant requirement hidden
+   = note: required because of the requirements on the impl of `QuerySource` for `JoinOn<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>`
+   = note: required because of the requirements on the impl of `InternalJoinDsl<SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, LeftOuter, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>` for `SelectStatement<FromClause<users::table>>`
+   = note: 1 redundant requirement hidden
+   = note: required because of the requirements on the impl of `InternalJoinDsl<SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, LeftOuter, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>` for `users::table`
+   = note: this error originates in the macro `$crate::__diesel_column` which comes from the expansion of the macro `table` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0271]: type mismatch resolving `<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, LeftOuter> as AppearsInFromClause<users::table>>::Count == diesel::query_source::Once`
+  --> tests/fail/invalid_joins.rs:58:26
+   |
+58 |     let _ = users::table.left_join(posts::table.left_join(users::table));
+   |                          ^^^^^^^^^ expected struct `MoreThanOnce`, found struct `diesel::query_source::Once`
+   |
+note: required because of the requirements on the impl of `AppearsOnTable<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, LeftOuter>>` for `users::columns::id`
+  --> tests/fail/invalid_joins.rs:5:1
+   |
+5  | / table! {
+6  | |     users {
+7  | |         id -> Integer,
+8  | |         name -> VarChar,
+9  | |     }
+10 | | }
+   | |_^
+   = note: 3 redundant requirements hidden
+   = note: required because of the requirements on the impl of `AppearsOnTable<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, LeftOuter>>` for `diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>`
+   = note: required because of the requirements on the impl of `QuerySource` for `JoinOn<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>`
+   = note: required because of the requirements on the impl of `InternalJoinDsl<SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, LeftOuter, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>` for `SelectStatement<FromClause<users::table>>`
+   = note: this error originates in the macro `$crate::__diesel_column` which comes from the expansion of the macro `table` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0271]: type mismatch resolving `<diesel::query_source::Once as Plus<diesel::query_source::Once>>::Output == diesel::query_source::Once`
+  --> tests/fail/invalid_joins.rs:61:26
+   |
+61 |     let _ = users::table.left_join(posts::table.left_join(users::table.on(posts::user_id.eq(users::id))));
+   |                          ^^^^^^^^^ expected struct `MoreThanOnce`, found struct `diesel::query_source::Once`
+   |
+note: required because of the requirements on the impl of `AppearsOnTable<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<posts::columns::user_id, users::columns::id>>>>>, LeftOuter>>` for `users::columns::id`
+  --> tests/fail/invalid_joins.rs:5:1
+   |
+5  | / table! {
+6  | |     users {
+7  | |         id -> Integer,
+8  | |         name -> VarChar,
+9  | |     }
+10 | | }
+   | |_^
+   = note: 2 redundant requirements hidden
+   = note: required because of the requirements on the impl of `AppearsOnTable<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<posts::columns::user_id, users::columns::id>>>>>, LeftOuter>>` for `((users::columns::id, users::columns::name), NullableExpression<query_source::joins::private::SkipSelectableExpressionBoundCheckWrapper<((posts::columns::id, posts::columns::title, posts::columns::user_id), NullableExpression<(users::columns::id, users::columns::name)>)>>)`
+   = note: required because of the requirements on the impl of `QuerySource` for `query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<posts::columns::user_id, users::columns::id>>>>>, LeftOuter>`
+   = note: 1 redundant requirement hidden
+   = note: required because of the requirements on the impl of `QuerySource` for `JoinOn<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<posts::columns::user_id, users::columns::id>>>>>, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>`
+   = note: required because of the requirements on the impl of `InternalJoinDsl<SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<posts::columns::user_id, users::columns::id>>>>>, LeftOuter, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>` for `SelectStatement<FromClause<users::table>>`
+   = note: this error originates in the macro `$crate::__diesel_column` which comes from the expansion of the macro `table` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0271]: type mismatch resolving `<diesel::query_source::Once as Plus<diesel::query_source::Once>>::Output == diesel::query_source::Once`
+  --> tests/fail/invalid_joins.rs:61:36
+   |
+61 |     let _ = users::table.left_join(posts::table.left_join(users::table.on(posts::user_id.eq(users::id))));
+   |                          --------- ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected struct `MoreThanOnce`, found struct `diesel::query_source::Once`
+   |                          |
+   |                          required by a bound introduced by this call
+   |
+note: required because of the requirements on the impl of `AppearsOnTable<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<posts::columns::user_id, users::columns::id>>>>>, LeftOuter>>` for `users::columns::id`
+  --> tests/fail/invalid_joins.rs:5:1
+   |
+5  | / table! {
+6  | |     users {
+7  | |         id -> Integer,
+8  | |         name -> VarChar,
+9  | |     }
+10 | | }
+   | |_^
+   = note: 2 redundant requirements hidden
+   = note: required because of the requirements on the impl of `AppearsOnTable<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<posts::columns::user_id, users::columns::id>>>>>, LeftOuter>>` for `((users::columns::id, users::columns::name), NullableExpression<query_source::joins::private::SkipSelectableExpressionBoundCheckWrapper<((posts::columns::id, posts::columns::title, posts::columns::user_id), NullableExpression<(users::columns::id, users::columns::name)>)>>)`
+   = note: required because of the requirements on the impl of `QuerySource` for `query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<posts::columns::user_id, users::columns::id>>>>>, LeftOuter>`
+   = note: 1 redundant requirement hidden
+   = note: required because of the requirements on the impl of `QuerySource` for `JoinOn<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<posts::columns::user_id, users::columns::id>>>>>, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>`
+   = note: required because of the requirements on the impl of `InternalJoinDsl<SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<posts::columns::user_id, users::columns::id>>>>>, LeftOuter, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>` for `SelectStatement<FromClause<users::table>>`
+   = note: 1 redundant requirement hidden
+   = note: required because of the requirements on the impl of `InternalJoinDsl<SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<posts::columns::user_id, users::columns::id>>>>>, LeftOuter, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>` for `users::table`
+   = note: this error originates in the macro `$crate::__diesel_column` which comes from the expansion of the macro `table` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0271]: type mismatch resolving `<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<posts::columns::user_id, users::columns::id>>>>>, LeftOuter> as AppearsInFromClause<users::table>>::Count == diesel::query_source::Once`
+  --> tests/fail/invalid_joins.rs:61:26
+   |
+61 |     let _ = users::table.left_join(posts::table.left_join(users::table.on(posts::user_id.eq(users::id))));
+   |                          ^^^^^^^^^ expected struct `MoreThanOnce`, found struct `diesel::query_source::Once`
+   |
+note: required because of the requirements on the impl of `AppearsOnTable<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<posts::columns::user_id, users::columns::id>>>>>, LeftOuter>>` for `users::columns::id`
+  --> tests/fail/invalid_joins.rs:5:1
+   |
+5  | / table! {
+6  | |     users {
+7  | |         id -> Integer,
+8  | |         name -> VarChar,
+9  | |     }
+10 | | }
+   | |_^
+   = note: 3 redundant requirements hidden
+   = note: required because of the requirements on the impl of `AppearsOnTable<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<posts::columns::user_id, users::columns::id>>>>>, LeftOuter>>` for `diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>`
+   = note: required because of the requirements on the impl of `QuerySource` for `JoinOn<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<posts::columns::user_id, users::columns::id>>>>>, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>`
+   = note: required because of the requirements on the impl of `InternalJoinDsl<SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<posts::columns::user_id, users::columns::id>>>>>, LeftOuter, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>` for `SelectStatement<FromClause<users::table>>`
+   = note: this error originates in the macro `$crate::__diesel_column` which comes from the expansion of the macro `table` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0271]: type mismatch resolving `<diesel::query_source::Once as Plus<diesel::query_source::Once>>::Output == diesel::query_source::Once`
+  --> tests/fail/invalid_joins.rs:64:26
+   |
+64 |     let _ = users::table.left_join(posts::table.on(users::id.eq(posts::user_id)).left_join(users::table));
+   |                          ^^^^^^^^^ expected struct `MoreThanOnce`, found struct `diesel::query_source::Once`
+   |
+note: required because of the requirements on the impl of `AppearsOnTable<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, LeftOuter>>` for `users::columns::id`
+  --> tests/fail/invalid_joins.rs:5:1
+   |
+5  | / table! {
+6  | |     users {
+7  | |         id -> Integer,
+8  | |         name -> VarChar,
+9  | |     }
+10 | | }
+   | |_^
+   = note: 2 redundant requirements hidden
+   = note: required because of the requirements on the impl of `AppearsOnTable<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, LeftOuter>>` for `((users::columns::id, users::columns::name), NullableExpression<query_source::joins::private::SkipSelectableExpressionBoundCheckWrapper<((posts::columns::id, posts::columns::title, posts::columns::user_id), NullableExpression<(users::columns::id, users::columns::name)>)>>)`
+   = note: required because of the requirements on the impl of `QuerySource` for `query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, LeftOuter>`
+   = note: 1 redundant requirement hidden
+   = note: required because of the requirements on the impl of `QuerySource` for `JoinOn<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<users::columns::id, posts::columns::user_id>>>`
+   = note: required because of the requirements on the impl of `InternalJoinDsl<SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, LeftOuter, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<users::columns::id, posts::columns::user_id>>>` for `SelectStatement<FromClause<users::table>>`
+   = note: this error originates in the macro `$crate::__diesel_column` which comes from the expansion of the macro `table` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0271]: type mismatch resolving `<diesel::query_source::Once as Plus<diesel::query_source::Once>>::Output == diesel::query_source::Once`
+  --> tests/fail/invalid_joins.rs:64:36
+   |
+64 |     let _ = users::table.left_join(posts::table.on(users::id.eq(posts::user_id)).left_join(users::table));
+   |                          --------- ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected struct `MoreThanOnce`, found struct `diesel::query_source::Once`
+   |                          |
+   |                          required by a bound introduced by this call
+   |
+note: required because of the requirements on the impl of `AppearsOnTable<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, LeftOuter>>` for `users::columns::id`
+  --> tests/fail/invalid_joins.rs:5:1
+   |
+5  | / table! {
+6  | |     users {
+7  | |         id -> Integer,
+8  | |         name -> VarChar,
+9  | |     }
+10 | | }
+   | |_^
+   = note: 2 redundant requirements hidden
+   = note: required because of the requirements on the impl of `AppearsOnTable<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, LeftOuter>>` for `((users::columns::id, users::columns::name), NullableExpression<query_source::joins::private::SkipSelectableExpressionBoundCheckWrapper<((posts::columns::id, posts::columns::title, posts::columns::user_id), NullableExpression<(users::columns::id, users::columns::name)>)>>)`
+   = note: required because of the requirements on the impl of `QuerySource` for `query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, LeftOuter>`
+   = note: 1 redundant requirement hidden
+   = note: required because of the requirements on the impl of `QuerySource` for `JoinOn<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<users::columns::id, posts::columns::user_id>>>`
+   = note: required because of the requirements on the impl of `InternalJoinDsl<SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, LeftOuter, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<users::columns::id, posts::columns::user_id>>>` for `SelectStatement<FromClause<users::table>>`
+   = note: 1 redundant requirement hidden
+   = note: required because of the requirements on the impl of `InternalJoinDsl<SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, LeftOuter, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<users::columns::id, posts::columns::user_id>>>` for `users::table`
+   = note: this error originates in the macro `$crate::__diesel_column` which comes from the expansion of the macro `table` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0271]: type mismatch resolving `<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, LeftOuter> as AppearsInFromClause<users::table>>::Count == diesel::query_source::Once`
+  --> tests/fail/invalid_joins.rs:64:26
+   |
+64 |     let _ = users::table.left_join(posts::table.on(users::id.eq(posts::user_id)).left_join(users::table));
+   |                          ^^^^^^^^^ expected struct `MoreThanOnce`, found struct `diesel::query_source::Once`
+   |
+note: required because of the requirements on the impl of `AppearsOnTable<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, LeftOuter>>` for `users::columns::id`
+  --> tests/fail/invalid_joins.rs:5:1
+   |
+5  | / table! {
+6  | |     users {
+7  | |         id -> Integer,
+8  | |         name -> VarChar,
+9  | |     }
+10 | | }
+   | |_^
+   = note: 2 redundant requirements hidden
+   = note: required because of the requirements on the impl of `AppearsOnTable<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, LeftOuter>>` for `diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<users::columns::id, posts::columns::user_id>>`
+   = note: required because of the requirements on the impl of `QuerySource` for `JoinOn<query_source::joins::Join<users::table, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<users::columns::id, posts::columns::user_id>>>`
+   = note: required because of the requirements on the impl of `InternalJoinDsl<SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, users::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>>>, LeftOuter, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<users::columns::id, posts::columns::user_id>>>` for `SelectStatement<FromClause<users::table>>`
+   = note: this error originates in the macro `$crate::__diesel_column` which comes from the expansion of the macro `table` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0271]: type mismatch resolving `<diesel::query_source::Once as Plus<diesel::query_source::Once>>::Output == diesel::query_source::Once`
+  --> tests/fail/invalid_joins.rs:67:53
+   |
+67 |     let _ = users::table.left_join(comments::table).left_join(posts::table.left_join(comments::table));
+   |                                                     ^^^^^^^^^ expected struct `MoreThanOnce`, found struct `diesel::query_source::Once`
+   |
+note: required because of the requirements on the impl of `AppearsOnTable<query_source::joins::Join<JoinOn<query_source::joins::Join<users::table, comments::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<comments::columns::user_id>, NullableExpression<users::columns::id>>>>, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, comments::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<comments::columns::post_id>, NullableExpression<posts::columns::id>>>>>>, LeftOuter>>` for `comments::columns::id`
+  --> tests/fail/invalid_joins.rs:20:1
+   |
+20 | / table! {
+21 | |     comments {
+22 | |         id -> Integer,
+23 | |         user_id -> Integer,
+...  |
+26 | |     }
+27 | | }
+   | |_^
+   = note: 3 redundant requirements hidden
+   = note: required because of the requirements on the impl of `AppearsOnTable<query_source::joins::Join<JoinOn<query_source::joins::Join<users::table, comments::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<comments::columns::user_id>, NullableExpression<users::columns::id>>>>, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, comments::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<comments::columns::post_id>, NullableExpression<posts::columns::id>>>>>>, LeftOuter>>` for `((users::columns::id, users::columns::name), NullableExpression<(comments::columns::id, comments::columns::user_id, comments::columns::post_id, comments::columns::name)>, NullableExpression<query_source::joins::private::SkipSelectableExpressionBoundCheckWrapper<((posts::columns::id, posts::columns::title, posts::columns::user_id), NullableExpression<(comments::columns::id, comments::columns::user_id, comments::columns::post_id, comments::columns::name)>)>>)`
+   = note: required because of the requirements on the impl of `QuerySource` for `query_source::joins::Join<JoinOn<query_source::joins::Join<users::table, comments::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<comments::columns::user_id>, NullableExpression<users::columns::id>>>>, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, comments::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<comments::columns::post_id>, NullableExpression<posts::columns::id>>>>>>, LeftOuter>`
+   = note: 1 redundant requirement hidden
+   = note: required because of the requirements on the impl of `QuerySource` for `JoinOn<query_source::joins::Join<JoinOn<query_source::joins::Join<users::table, comments::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<comments::columns::user_id>, NullableExpression<users::columns::id>>>>, SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, comments::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<comments::columns::post_id>, NullableExpression<posts::columns::id>>>>>>, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>`
+   = note: required because of the requirements on the impl of `InternalJoinDsl<SelectStatement<FromClause<JoinOn<query_source::joins::Join<posts::table, comments::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<comments::columns::post_id>, NullableExpression<posts::columns::id>>>>>>, LeftOuter, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<posts::columns::user_id>, NullableExpression<users::columns::id>>>>` for `SelectStatement<FromClause<JoinOn<query_source::joins::Join<users::table, comments::table, LeftOuter>, diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<NullableExpression<comments::columns::user_id>, NullableExpression<users::columns::id>>>>>>`
+   = note: this error originates in the macro `$crate::__diesel_column` which comes from the expansion of the macro `table` (in Nightly builds, run with -Z macro-backtrace for more info)