`Extract#as` should not mutate the receiver

Fixes https://github.com/rails/rails/issues/16913

2 files changed, 4 insertions, 18 deletions

diff --git a/lib/arel/nodes/extract.rb b/lib/arel/nodes/extract.rb
index 64f5c3ff0f..7c69deadef 100644
--- a/lib/arel/nodes/extract.rb
+++ b/lib/arel/nodes/extract.rb
@@ -1,20 +1,14 @@
 module Arel
   module Nodes
     class Extract < Arel::Nodes::Unary
+      include Arel::AliasPredication
       include Arel::Predications
 
       attr_accessor :field
-      attr_accessor :alias
 
-      def initialize expr, field, aliaz = nil
+      def initialize expr, field
         super(expr)
         @field = field
-        @alias = aliaz && SqlLiteral.new(aliaz)
-      end
-
-      def as aliaz
-        self.alias = SqlLiteral.new(aliaz)
-        self
       end
 
       def hash
@@ -23,8 +17,7 @@ module Arel
 
       def eql? other
         super &&
-          self.field == other.field &&
-          self.alias == other.alias
+          self.field == other.field
       end
       alias :== :eql?
     end
diff --git a/lib/arel/visitors/to_sql.rb b/lib/arel/visitors/to_sql.rb
index ae1b7930af..ca09373b64 100644
--- a/lib/arel/visitors/to_sql.rb
+++ b/lib/arel/visitors/to_sql.rb
@@ -475,14 +475,7 @@ module Arel
 
       def visit_Arel_Nodes_Extract o, collector
         collector << "EXTRACT(#{o.field.to_s.upcase} FROM "
-        collector = visit o.expr, collector
-        collector << ")"
-        if o.alias
-          collector << " AS "
-          visit o.alias, collector
-        else
-          collector
-        end
+        visit(o.expr, collector) << ")"
       end
 
       def visit_Arel_Nodes_Count o, collector