Reorganize node classes into new AST namespace

This change introduces a new `RuboCop::AST` namespace, and moves the
following classes into it:

 - `Node`
 - `Sexp`
 - `ArrayNode`, `HashNode`, `IfNode`, `ConditionalNode`, `ModifierNode`,
   `UntilNode`, `WhileNode`

It also renames the `ast_node` directory to `ast`, and `ast_node.rb` to
`node.rb`.

lib/rubocop.rb

@@ -19,17 +19,18 @@
 require 'rubocop/name_similarity'
 require 'rubocop/node_pattern'
 require 'rubocop/string_interpreter'
-require 'rubocop/ast_node/sexp'
-require 'rubocop/ast_node'
-require 'rubocop/ast_node/node_extensions/conditional_node'
-require 'rubocop/ast_node/node_extensions/modifier_node'
-require 'rubocop/ast_node/node_extensions/array_node'
-require 'rubocop/ast_node/node_extensions/hash_node'
-require 'rubocop/ast_node/node_extensions/if_node'
-require 'rubocop/ast_node/node_extensions/until_node'
-require 'rubocop/ast_node/node_extensions/while_node'
-require 'rubocop/ast_node/builder'
-require 'rubocop/ast_node/traversal'
+require 'rubocop/ast/sexp'
+require 'rubocop/ast/node'
+require 'rubocop/ast/node/mixin/conditional_node'
+require 'rubocop/ast/node/mixin/modifier_node'
+require 'rubocop/ast/node/array_node'
+require 'rubocop/ast/node/case_node'
+require 'rubocop/ast/node/hash_node'
+require 'rubocop/ast/node/if_node'
+require 'rubocop/ast/node/until_node'
+require 'rubocop/ast/node/while_node'
+require 'rubocop/ast/builder'
+require 'rubocop/ast/traversal'
 require 'rubocop/error'
 require 'rubocop/warning'
 

lib/rubocop/ast_node/builder.rb → lib/rubocop/ast/builder.rb

@@ -1,9 +1,9 @@
 # frozen_string_literal: true
 
 module RuboCop
-  class Node
+  module AST
     # `RuboCop::Builder` is an AST builder that is utilized to let `Parser`
-    # generate ASTs with {RuboCop::Node}.
+    # generate ASTs with {RuboCop::AST::Node}.
     #
     # @example
     #   buffer = Parser::Source::Buffer.new('(string)')
@@ -28,11 +28,11 @@ def string_value(token)
 
       def node_map(type)
         case type
-        when :array then RuboCop::NodeExtension::ArrayNode
-        when :hash  then RuboCop::NodeExtension::HashNode
-        when :if    then RuboCop::NodeExtension::IfNode
-        when :until, :until_post then RuboCop::NodeExtension::UntilNode
-        when :while, :while_post then RuboCop::NodeExtension::WhileNode
+        when :array then ArrayNode
+        when :hash  then HashNode
+        when :if    then IfNode
+        when :until, :until_post then UntilNode
+        when :while, :while_post then WhileNode
         else Node
         end
       end

lib/rubocop/ast/node.rb

@@ -142,7 +142,7 @@ def sibling_index
       def each_ancestor(*types, &block)
         return to_enum(__method__, *types) unless block_given?
 
-        visit_ancestors_with_types(types, &block)
+        visit_ancestors(types, &block)
 
         self
       end
@@ -422,6 +422,7 @@ def binary_operation?
 
       def chained?
         return false unless argument?
+
         receiver, _method_name, *_args = *parent
         equal?(receiver)
       end
@@ -523,7 +524,7 @@ def visit_descendants(types, &block)
 
       private
 
-      def visit_ancestors_with_types(types)
+      def visit_ancestors(types)
         last_node = self
 
         while (current_node = last_node.parent)

lib/rubocop/ast_node/node_extensions/array_node.rb → lib/rubocop/ast/node/array_node.rb

@@ -1,9 +1,9 @@
 # frozen_string_literal: true
 
 module RuboCop
-  module NodeExtension
+  module AST
     # A node extension for `array` nodes.
-    class ArrayNode < RuboCop::Node
+    class ArrayNode < Node
       PERCENT_LITERAL_TYPES = {
         string: /^%[wW]/,
         symbol: /^%[iI]/

lib/rubocop/ast_node/node_extensions/hash_node.rb → lib/rubocop/ast/node/hash_node.rb

@@ -1,9 +1,9 @@
 # frozen_string_literal: true
 
 module RuboCop
-  module NodeExtension
+  module AST
     # A node extension for `hash` nodes.
-    class HashNode < RuboCop::Node
+    class HashNode < Node
       def pairs
         each_pair.to_a
       end

lib/rubocop/ast_node/node_extensions/if_node.rb → lib/rubocop/ast/node/if_node.rb

@@ -1,9 +1,9 @@
 # frozen_string_literal: true
 
 module RuboCop
-  module NodeExtension
+  module AST
     # A node extension for `if` nodes.
-    class IfNode < RuboCop::Node
+    class IfNode < Node
       include ConditionalNode
       include ModifierNode
 

lib/rubocop/ast_node/node_extensions/conditional_node.rb → lib/rubocop/ast/node/mixin/conditional_node.rb

@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 module RuboCop
-  module NodeExtension
+  module AST
     # Common functionality for nodes that have conditions:
     # `if`, `while`, `until`, `case`
     module ConditionalNode

lib/rubocop/ast_node/node_extensions/modifier_node.rb → lib/rubocop/ast/node/mixin/modifier_node.rb

@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 module RuboCop
-  module NodeExtension
+  module AST
     # Common functionality for nodes that can be used as modifiers:
     # `if`, `while`, `until`
     module ModifierNode

lib/rubocop/ast/node/until_node.rb

@@ -11,10 +11,6 @@ def keyword
         'until'
       end
 
-      def inverse_keyword
-        'while'
-      end
-
       def do?
         loc.begin && loc.begin.is?('do')
       end

lib/rubocop/ast_node/node_extensions/until_node.rb → lib/rubocop/ast/node/until_node.rb~HEAD

@@ -1,16 +1,20 @@
 # frozen_string_literal: true
 
 module RuboCop
-  module NodeExtension
+  module AST
     # A node extension for `until` nodes.
-    class UntilNode < RuboCop::Node
+    class UntilNode < Node
       include ConditionalNode
       include ModifierNode
 
       def keyword
         'until'
       end
 
+      def inverse_keyword
+        'while'
+      end
+
       def do?
         loc.begin && loc.begin.is?('do')
       end

lib/rubocop/ast/node/while_node.rb

@@ -11,10 +11,6 @@ def keyword
         'while'
       end
 
-      def inverse_keyword
-        'until'
-      end
-
       def do?
         loc.begin && loc.begin.is?('do')
       end

lib/rubocop/ast_node/node_extensions/while_node.rb → lib/rubocop/ast/node/while_node.rb~HEAD

@@ -1,16 +1,20 @@
 # frozen_string_literal: true
 
 module RuboCop
-  module NodeExtension
+  module AST
     # A node extension for `while` nodes.
-    class WhileNode < RuboCop::Node
+    class WhileNode < Node
       include ConditionalNode
       include ModifierNode
 
       def keyword
         'while'
       end
 
+      def inverse_keyword
+        'until'
+      end
+
       def do?
         loc.begin && loc.begin.is?('do')
       end

lib/rubocop/ast/sexp.rb

@@ -0,0 +1,16 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module AST
+    # This module provides a shorthand method to create a {Node} like
+    # `Parser::AST::Sexp`.
+    #
+    # @see http://rubydoc.info/gems/ast/AST/Sexp
+    module Sexp
+      # Creates a {Node} with type `type` and children `children`.
+      def s(type, *children)
+        Node.new(type, children)
+      end
+    end
+  end
+end

lib/rubocop/ast_node/traversal.rb → lib/rubocop/ast/traversal.rb

@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 module RuboCop
-  class Node
+  module AST
     # Provides methods for traversing an AST.
     # Does not transform an AST; for that, use Parser::AST::Processor.
     # Override methods to perform custom processing. Remember to call `super`