Do not pass AR object to Arel quotes

app/models/concerns/issuable.rb

@@ -103,7 +103,7 @@ module Issuable
     end
     scope :assigned_to, ->(u) do
       assignees_table = Arel::Table.new("#{to_ability_name}_assignees")
-      sql = assignees_table.project('true').where(assignees_table[:user_id].in(u)).where(Arel::Nodes::SqlLiteral.new("#{to_ability_name}_id = #{to_ability_name}s.id"))
+      sql = assignees_table.project('true').where(assignees_table[:user_id].in(u.id)).where(Arel::Nodes::SqlLiteral.new("#{to_ability_name}_id = #{to_ability_name}s.id"))
       where("EXISTS (#{sql.to_sql})")
     end
     # rubocop:enable GitlabSecurity/SqlInjection

app/models/merge_request.rb

@@ -381,7 +381,7 @@ class MergeRequest < ApplicationRecord
   scope :review_requested_to, ->(user) do
     where(
       reviewers_subquery
-        .where(Arel::Table.new("#{to_ability_name}_reviewers")[:user_id].eq(user))
+        .where(Arel::Table.new("#{to_ability_name}_reviewers")[:user_id].eq(user.id))
         .exists
     )
   end
@@ -389,7 +389,7 @@ class MergeRequest < ApplicationRecord
   scope :no_review_requested_to, ->(user) do
     where(
       reviewers_subquery
-        .where(Arel::Table.new("#{to_ability_name}_reviewers")[:user_id].eq(user))
+        .where(Arel::Table.new("#{to_ability_name}_reviewers")[:user_id].eq(user.id))
         .exists
         .not
     )