Delegate `ast` and `locked` to `arel` explicitly

Currently `ast` and `locked` are used in the internal but delegating to
`arel` is depend on `method_missing`. If a model class is defined these
methods, `select_all` will be broken.

It should be delegated to `arel` explicitly.

2 files changed, 10 insertions, 1 deletions

diff --git a/activerecord/test/cases/relation/merging_test.rb b/activerecord/test/cases/relation/merging_test.rb
index 64866eaf2d..c3b39a9295 100644
--- a/activerecord/test/cases/relation/merging_test.rb
+++ b/activerecord/test/cases/relation/merging_test.rb
@@ -56,7 +56,7 @@ class RelationMergingTest < ActiveRecord::TestCase
 
   def test_relation_merging_with_locks
     devs = Developer.lock.where("salary >= 80000").order("id DESC").merge(Developer.limit(2))
-    assert devs.locked.present?
+    assert devs.locked?
   end
 
   def test_relation_merging_with_preload
diff --git a/activerecord/test/models/category.rb b/activerecord/test/models/category.rb
index e8654dca01..4b2840c653 100644
--- a/activerecord/test/models/category.rb
+++ b/activerecord/test/models/category.rb
@@ -29,6 +29,15 @@ class Category < ActiveRecord::Base
   has_many :authors_with_select, -> { select "authors.*, categorizations.post_id" }, through: :categorizations, source: :author
 
   scope :general, -> { where(name: "General") }
+
+  # Should be delegated `ast` and `locked` to `arel`.
+  def self.ast
+    raise
+  end
+
+  def self.locked
+    raise
+  end
 end
 
 class SpecialCategory < Category