Introduce AST::Meta to externalize semantic analysis

* Add Mutant::AST namespace to hold all AST related data / helpers.
* Mutant::AST will be externalized into an ast-meta gem that can be
  shared with unparser for deduplication.
* Over the time the mutators itself will not need to deal with semantic
  analysis of the AST anymore by themselves.
* Move AST analysis for send nodes to AST::Meta
* Fix #209

config/flay.yml

@@ -1,3 +1,3 @@
 ---
 threshold: 18
-total_score: 960
+total_score: 977

config/reek.yml

@@ -113,7 +113,7 @@ UncommunicativeMethodName:
   enabled: true
   exclude:
   - Mutant::Mutation#sha1
-  - Mutant::NodeHelpers#s
+  - Mutant::AST::Sexp#s
   reject:
   - !ruby/regexp /^[a-z]$/
   - !ruby/regexp /[0-9]$/
@@ -159,5 +159,5 @@ UtilityFunction:
   - Mutant::Meta::Example::Verification#format_mutation
   - Mutant::Mutation::Evil#success?
   - Mutant::Mutation::Neutral#success?
-  - Mutant::NodeHelpers#s
+  - Mutant::AST::Sexp#s
   max_helper_calls: 0

lib/mutant.rb

@@ -25,45 +25,8 @@ module Mutant
   # The frozen empty array used within mutant
   EMPTY_ARRAY = [].freeze
 
-  symbolset = ->(strings) { strings.map(&:to_sym).to_set.freeze }
-
   SCOPE_OPERATOR = '::'.freeze
 
-  # Set of nodes that cannot be on the LHS of an assignment
-  NOT_ASSIGNABLE         = symbolset.(%w[int float str dstr class module self nil])
-  # Set of op-assign types
-  OP_ASSIGN              = symbolset.call(%w[or_asgn and_asgn op_asgn])
-  # Set of node types that are not valid when emitted standalone
-  NOT_STANDALONE         = symbolset.(%w[splat restarg block_pass])
-  INDEX_OPERATORS        = symbolset.(%w[[] []=])
-  UNARY_METHOD_OPERATORS = symbolset.(%w[~@ +@ -@ !])
-
-  # Operators ruby implementeds as methods
-  METHOD_OPERATORS = symbolset.(%w[
-    <=> === []= [] <= >= == !~ != =~ <<
-    >> ** * % /  | ^ & < > + - ~@ +@ -@ !
-  ])
-
-  BINARY_METHOD_OPERATORS = (
-    METHOD_OPERATORS - (INDEX_OPERATORS + UNARY_METHOD_OPERATORS)
-  ).to_set.freeze
-
-  OPERATOR_METHODS = (
-    METHOD_OPERATORS + INDEX_OPERATORS + UNARY_METHOD_OPERATORS
-  ).to_set.freeze
-
-  # Nodes that are NOT handled by mutant.
-  #
-  # not - 1.8 only, mutant does not support 1.8
-  #
-  NODE_BLACKLIST = symbolset.(%w[not])
-
-  # Nodes that are NOT generated by parser but used by mutant / unparser.
-  NODE_EXTRA = symbolset.(%w[empty])
-
-  # All node types mutant handles
-  NODE_TYPES = ((Parser::Meta::NODE_TYPES + NODE_EXTRA) - NODE_BLACKLIST).to_set.freeze
-
   # Lookup constant for location
   #
   # @param [String] location
@@ -116,9 +79,15 @@ module Mutant
 end # Mutant
 
 require 'mutant/version'
+require 'mutant/ast'
+require 'mutant/ast/sexp'
+require 'mutant/ast/types'
+require 'mutant/ast/nodes'
+require 'mutant/ast/named_children'
+require 'mutant/ast/node_predicates'
+require 'mutant/ast/meta'
 require 'mutant/cache'
 require 'mutant/delegator'
-require 'mutant/node_helpers'
 require 'mutant/warning_filter'
 require 'mutant/warning_expectation'
 require 'mutant/walker'

lib/mutant/ast.rb

@@ -0,0 +1,5 @@
+module Mutant
+  # AST helpers
+  module AST
+  end # AST
+end # Mutant

lib/mutant/ast/meta.rb

@@ -0,0 +1,131 @@
+module Mutant
+  module AST
+    # Node meta information mixin
+    module Meta
+
+      REGISTRY = {}
+
+      # Return meta for node
+      #
+      # @param [Parser::AST::Node] node
+      #
+      # @return [Meta]
+      #
+      # @api private
+      #
+      def self.for(node)
+        REGISTRY.fetch(node.type, Generic).new(node)
+      end
+
+      # Generic metadata for send nodes
+      class Send
+        include Concord.new(:node), NamedChildren
+
+        children :receiver, :selector
+
+        REGISTRY[:send] = self
+
+        INDEX_ASSIGNMENT_SELECTOR            = :[]=
+        ATTRIBUTE_ASSIGNMENT_SELECTOR_SUFFIX = '='.freeze
+
+        # Return arguments
+        #
+        # @return [Enumerable<Parser::AST::Node>]
+        #
+        # @api private
+        #
+        alias_method :arguments, :remaining_children
+
+        # Test if AST node is a valid assignment target
+        #
+        # @return [Boolean]
+        #
+        # @api private
+        #
+        def assignment?
+          index_assignment? || attribute_assignment?
+        end
+
+        # Test if AST node is an attribute assignment?
+        #
+        # @return [Boolean]
+        #
+        # @api private
+        #
+        def attribute_assignment?
+          arguments.one? && attribute_assignment_selector?
+        end
+
+        # Test if AST node is an index assign
+        #
+        # @return [Boolean]
+        #
+        # @api private
+        #
+        def index_assignment?
+          arguments.length.equal?(2) && index_assignment_selector?
+        end
+
+        # Test for binary operator implemented as method
+        #
+        # @return [Boolean]
+        #
+        # @api private
+        #
+        def binary_method_operator?
+          arguments.one? && Types::BINARY_METHOD_OPERATORS.include?(selector)
+        end
+
+        # Test if node is part of an mlhs
+        #
+        # @return [Boolean]
+        #
+        # @api private
+        #
+        def mlhs?
+          (index_assignment_selector? && arguments.one?) || (arguments.empty? && attribute_assignment_selector?)
+        end
+
+      private
+
+        # Test for index assignment operator
+        #
+        # @return [Boolean]
+        #
+        # @api private
+        #
+        def index_assignment_selector?
+          selector.equal?(INDEX_ASSIGNMENT_SELECTOR)
+        end
+
+        # Test for attribute assignment selector
+        #
+        # @return [Boolean]
+        #
+        # @api private
+        #
+        def attribute_assignment_selector?
+          !Types::METHOD_OPERATORS.include?(selector) && selector.to_s.end_with?(ATTRIBUTE_ASSIGNMENT_SELECTOR_SUFFIX)
+        end
+
+      end # Send
+
+      # Generic node metatada
+      class Generic
+        include Adamantium, Concord.new(:node)
+
+        # Test if AST node is a valid assign target
+        #
+        # @return [Boolean]
+        #
+        # @api private
+        #
+        def assignment?
+          Types::ASSIGNABLE_VARIABLES.include?(node.type)
+        end
+
+      end # Generic
+
+    end #
+  end # AST
+end # Mutant

lib/mutant/ast/named_children.rb

@@ -0,0 +1,98 @@
+module Mutant
+  module AST
+
+    # Helper methods to define named children
+    module NamedChildren
+
+      # Hook called when module gets included
+      #
+      # @param [Class, Module] host
+      #
+      # @return [undefined]
+      #
+      # @api private
+      #
+      def self.included(host)
+        super
+        host.class_eval do
+          include InstanceMethods
+          extend ClassMethods
+        end
+      end
+
+      # Methods mixed int ot instance level
+      module InstanceMethods
+
+      private
+
+        # Return children
+        #
+        # @return [Array<Parser::AST::Node]
+        #
+        # @api private
+        #
+        def children
+          node.children
+        end
+
+      end # InstanceMethods
+
+      # Methods mixed in at class level
+      module ClassMethods
+
+      private
+
+        # Define named child
+        #
+        # @param [Symbol] name
+        # @param [Fixnum] index
+        #
+        # @return [undefined]
+        #
+        # @api private
+        #
+        def define_named_child(name, index)
+          define_method(name) do
+            children.at(index)
+          end
+        end
+
+        # Define remaining children
+        #
+        # @param [Array<Symbol>] names
+        #
+        # @return [undefined]
+        #
+        # @api private
+        #
+        def define_remaining_children(names)
+          define_method(:remaining_children_with_index) do
+            children.each_with_index.drop(names.length)
+          end
+
+          define_method(:remaining_children_indices) do
+            children.each_index.drop(names.length)
+          end
+
+          define_method(:remaining_children) do
+            children.drop(names.length)
+          end
+        end
+
+        # Create name helpers
+        #
+        # @return [undefined]
+        #
+        # @api private
+        #
+        def children(*names)
+          names.each_with_index do |name, index|
+            define_named_child(name, index)
+          end
+          define_remaining_children(names)
+        end
+
+      end # ClassMethods
+    end # NamedChildren
+  end # AST
+end # Mutant

lib/mutant/ast/node_predicates.rb

@@ -0,0 +1,19 @@
+module Mutant
+  module AST
+    # Module for node predicates
+    module NodePredicates
+
+      Types::ALL.each do |type|
+        fail "method: #{type} is already defined" if instance_methods(true).include?(type)
+
+        name = "n_#{type.to_s.sub(/\??\z/, '?')}"
+
+        define_method(name) do |node|
+          node.type.equal?(type)
+        end
+        private name
+      end
+
+    end # NodePredicates
+  end # AST
+end # Mutant

lib/mutant/ast/nodes.rb

@@ -0,0 +1,21 @@
+module Mutant
+  module AST
+    # Singleton nodes
+    module Nodes
+      extend Sexp
+
+      N_NAN               = s(:send, s(:float,  0.0), :/, s(:float, 0.0))
+      N_INFINITY          = s(:send, s(:float,  1.0), :/, s(:float, 0.0))
+      N_NEGATIVE_INFINITY = s(:send, s(:float, -1.0), :/, s(:float, 0.0))
+      N_RAISE             = s(:send, nil, :raise)
+      N_TRUE              = s(:true)
+      N_FALSE             = s(:false)
+      N_NIL               = s(:nil)
+      N_EMPTY             = s(:empty)
+      N_SELF              = s(:self)
+      N_ZSUPER            = s(:zsuper)
+      N_EMPTY_SUPER       = s(:super)
+
+    end # Node
+  end # AST
+end # Mutant

lib/mutant/ast/sexp.rb

@@ -0,0 +1,34 @@
+module Mutant
+  module AST
+    # Mixin for node sexp syntax
+    module Sexp
+
+    private
+
+      # Build node
+      #
+      # @param [Symbol] type
+      #
+      # @return [Parser::AST::Node]
+      #
+      # @api private
+      #
+      def s(type, *children)
+        Parser::AST::Node.new(type, children)
+      end
+
+      # Build a negated boolean node
+      #
+      # @param [Parser::AST::Node] node
+      #
+      # @return [Parser::AST::Node]
+      #
+      # @api private
+      #
+      def n_not(node)
+        s(:send, node, :!)
+      end
+
+    end # Sexp
+  end # AST
+end # Mutant

lib/mutant/ast/types.rb

@@ -0,0 +1,48 @@
+module Mutant
+  module AST
+    # Groups of node types
+    module Types
+      symbolset = ->(strings) { strings.map(&:to_sym).to_set.freeze }
+
+      ASSIGNABLE_VARIABLES = symbolset.(%w[ivasgn lvasgn cvasgn gvasgn])
+
+      INDEX_ASSIGN_OPERATOR = :[]=
+
+      # Set of nodes that cannot be on the LHS of an assignment
+      NOT_ASSIGNABLE         = symbolset.(%w[int float str dstr class module self nil])
+
+      # Set of op-assign types
+      OP_ASSIGN              = symbolset.(%w[or_asgn and_asgn op_asgn])
+      # Set of node types that are not valid when emitted standalone
+      NOT_STANDALONE         = symbolset.(%w[splat restarg block_pass])
+      INDEX_OPERATORS        = symbolset.(%w[[] []=])
+      UNARY_METHOD_OPERATORS = symbolset.(%w[~@ +@ -@ !])
+
+      # Operators ruby implementeds as methods
+      METHOD_OPERATORS = symbolset.(%w[
+        <=> === []= [] <= >= == !~ != =~ <<
+        >> ** * % /  | ^ & < > + - ~@ +@ -@ !
+      ])
+
+      BINARY_METHOD_OPERATORS = (
+        METHOD_OPERATORS - (INDEX_OPERATORS + UNARY_METHOD_OPERATORS)
+      ).to_set.freeze
+
+      OPERATOR_METHODS = (
+        METHOD_OPERATORS + INDEX_OPERATORS + UNARY_METHOD_OPERATORS
+      ).to_set.freeze
+
+      # Nodes that are NOT handled by mutant.
+      #
+      # not - 1.8 only, mutant does not support 1.8
+      #
+      BLACKLIST = symbolset.(%w[not])
+
+      # Nodes that are NOT generated by parser but used by mutant / unparser.
+      EXTRA = symbolset.(%w[empty])
+
+      # All node types mutant handles
+      ALL = ((Parser::Meta::NODE_TYPES + EXTRA) - BLACKLIST).to_set.freeze
+    end # Types
+  end # AST
+end # Mutant

lib/mutant/cli.rb

@@ -4,7 +4,7 @@ module Mutant
 
   # Comandline parser
   class CLI
-    include Adamantium::Flat, Equalizer.new(:config), NodeHelpers
+    include Adamantium::Flat, Equalizer.new(:config)
 
     # Error raised when CLI argv is invalid
     Error = Class.new(RuntimeError)
@@ -186,7 +186,7 @@ module Mutant
         @builder.add_subject_ignore(Expression.parse(pattern))
       end
       opts.on('--code CODE', 'Scope execution to subjects with CODE') do |code|
-        @builder.add_subject_selector(Morpher.compile(s(:eql, s(:attribute, :code), s(:static, code))))
+        @builder.add_subject_selector(:code, code)
       end
     end
 

lib/mutant/context/scope.rb

@@ -3,7 +3,7 @@ module Mutant
     # Scope context for mutation (Class or Module)
     class Scope < self
       include Adamantium::Flat, Concord::Public.new(:scope, :source_path)
-      extend NodeHelpers
+      extend AST::Sexp
 
       NAMESPACE_DELIMITER = '::'.freeze
 

lib/mutant/expression.rb

@@ -10,7 +10,7 @@ module Mutant
 
     METHOD_NAME_PATTERN = Regexp.union(
       /[A-Za-z_][A-Za-z\d_]*[!?=]?/,
-      *OPERATOR_METHODS.map(&:to_s)
+      *AST::Types::OPERATOR_METHODS.map(&:to_s)
     ).freeze
 
     SCOPE_PATTERN = /#{SCOPE_NAME_PATTERN}(?:#{SCOPE_OPERATOR}#{SCOPE_NAME_PATTERN})*/.freeze

lib/mutant/matcher/builder.rb

@@ -2,7 +2,7 @@ module Mutant
   class Matcher
     # Builder for complex matchers
     class Builder
-      include NodeHelpers, Concord.new(:cache)
+      include Concord.new(:cache), AST::Sexp
 
       # Initalize object
       #
@@ -40,8 +40,8 @@ module Mutant
       #
       # @api private
       #
-      def add_subject_selector(selector)
-        @subject_selectors << selector
+      def add_subject_selector(attribute, value)
+        @subject_selectors << Morpher.compile(s(:eql, s(:attribute, attribute), s(:static, value)))
         self
       end
 

lib/mutant/meta.rb

@@ -1,7 +1,6 @@
 module Mutant
   # Namespace for mutant metadata
   module Meta
-
     require 'mutant/meta/example'
     require 'mutant/meta/example/dsl'
 

lib/mutant/meta/example/dsl.rb

@@ -4,7 +4,7 @@ module Mutant
 
       # Example DSL
       class DSL
-        include NodeHelpers
+        include AST::Sexp
 
         # Run DSL on block
         #

lib/mutant/mutator/node.rb

@@ -5,11 +5,13 @@ module Mutant
 
     # Abstract base class for node mutators
     class Node < self
-      include AbstractType, NodeHelpers, Unparser::Constants
+      include AbstractType, Unparser::Constants
+      include AST::NamedChildren, AST::NodePredicates, AST::Sexp, AST::Nodes
 
-      # Define named child
+      # Helper to define a named child
+      #
+      # @param [Parser::AST::Node] node
       #
-      # @param [Symbol] name
       # @param [Fixnum] index
       #
       # @return [undefined]
@@ -17,9 +19,7 @@ module Mutant
       # @api private
       #
       def self.define_named_child(name, index)
-        define_method(name) do
-          children.at(index)
-        end
+        super
 
         define_method("emit_#{name}_mutations") do |&block|
           mutate_child(index, &block)
@@ -29,43 +29,6 @@ module Mutant
           emit_child_update(index, node)
         end
       end
-      private_class_method :define_named_child
-
-      # Define remaining children
-      #
-      # @param [Array<Symbol>] names
-      #
-      # @return [undefined]
-      #
-      # @api private
-      #
-      def self.define_remaining_children(names)
-        define_method(:remaining_children_with_index) do
-          children.each_with_index.drop(names.length)
-        end
-
-        define_method(:remaining_children_indices) do
-          children.each_index.drop(names.length)
-        end
-
-        define_method(:remaining_children) do
-          children.drop(names.length)
-        end
-      end
-      private_class_method :define_remaining_children
-
-      # Create name helpers
-      #
-      # @return [undefined]
-      #
-      # @api private
-      #
-      def self.children(*names)
-        names.each_with_index do |name, index|
-          define_named_child(name, index)
-        end
-        define_remaining_children(names)
-      end
       private_class_method :children
 
     private
@@ -98,6 +61,15 @@ module Mutant
         end
       end
 
+      # Return ast meta description
+      #
+      # @return [AST::Meta]
+      #
+      def meta
+        AST::Meta.for(node)
+      end
+      memoize :meta
+
       # Return children
       #
       # @return [Array<Parser::AST::Node>]
@@ -246,7 +218,7 @@ module Mutant
       # @api private
       #
       def asgn_left?
-        OP_ASSIGN.include?(parent_type) && parent.node.children.first.equal?(node)
+        AST::Types::OP_ASSIGN.include?(parent_type) && parent.node.children.first.equal?(node)
       end
 
     end # Node

lib/mutant/mutator/node/or_asgn.rb

@@ -22,7 +22,7 @@ module Mutant
           emit_right_mutations
           return if n_ivasgn?(left)
           emit_left_mutations do |node|
-            !n_self?(node)
+            AST::Meta.for(node).assignment?
           end
         end
 

lib/mutant/mutator/node/send.rb

@@ -4,6 +4,7 @@ module Mutant
 
       # Namespace for send mutators
       class Send < self
+        include AST::Types
 
         handle(:send)
 
@@ -19,12 +20,6 @@ module Mutant
           :== =>        [:eql?, :equal?]
         )
 
-        INDEX_REFERENCE      = :[]
-        INDEX_ASSIGN         = :[]=
-        VARIABLE_ASSIGN      = :'='
-        ASSIGNMENT_OPERATORS = [INDEX_ASSIGN, VARIABLE_ASSIGN].to_set.freeze
-        ATTRIBUTE_ASSIGNMENT = /\A[a-z\d_]+=\z/.freeze
-
       private
 
         # Perform dispatch
@@ -35,7 +30,7 @@ module Mutant
         #
         def dispatch
           emit_singletons
-          if selector.equal?(INDEX_ASSIGN)
+          if meta.index_assignment?
             run(Index::Assign)
           else
             non_index_dispatch
@@ -50,9 +45,9 @@ module Mutant
         #
         def non_index_dispatch
           case
-          when binary_operator?
+          when meta.binary_method_operator?
             run(Binary)
-          when attribute_assignment?
+          when meta.attribute_assignment?
             run(AttributeAssignment)
           else
             normal_dispatch
@@ -103,26 +98,6 @@ module Mutant
           emit(receiver) if receiver && !NOT_ASSIGNABLE.include?(receiver.type)
         end
 
-        # Test for binary operator
-        #
-        # @return [Boolean]
-        #
-        # @api private
-        #
-        def binary_operator?
-          arguments.one? && BINARY_METHOD_OPERATORS.include?(selector)
-        end
-
-        # Test for attribute assignment
-        #
-        # @return [Boolean]
-        #
-        # @api private
-        #
-        def attribute_assignment?
-          arguments.one? && ATTRIBUTE_ASSIGNMENT =~ selector
-        end
-
         # Mutate arguments
         #
         # @return [undefined]
@@ -173,40 +148,10 @@ module Mutant
             KEYWORDS.include?(selector)         ||
             METHOD_OPERATORS.include?(selector) ||
             OP_ASSIGN.include?(parent_type)     ||
-            attribute_assignment?
+            meta.attribute_assignment?
           )
         end
 
-        # Test for assignment
-        #
-        # @return [Boolean]
-        #
-        # @api private
-        #
-        def assignment?
-          arguments.one? && (ASSIGNMENT_OPERATORS.include?(selector) || attribute_assignment?)
-        end
-
-        # Test if node is part of an mlhs
-        #
-        # @return [Boolean]
-        #
-        # @api private
-        #
-        def mlhs?
-          assignment? && !arguments?
-        end
-
-        # Test for empty arguments
-        #
-        # @return [Boolean]
-        #
-        # @api private
-        #
-        def arguments?
-          arguments.any?
-        end
-
       end # Send
     end # Node
   end # Mutator

lib/mutant/mutator/node/super.rb

@@ -7,9 +7,6 @@ module Mutant
 
         handle(:super)
 
-        Z_SUPER = NodeHelpers.s(:zsuper)
-        EMPTY_SUPER = NodeHelpers.s(:super)
-
       private
 
         # Emit mutations
@@ -20,8 +17,8 @@ module Mutant
         #
         def dispatch
           emit_singletons
-          emit(Z_SUPER)
-          emit(EMPTY_SUPER)
+          emit(N_ZSUPER)
+          emit(N_EMPTY_SUPER)
           children.each_index do |index|
             mutate_child(index)
             delete_child(index)

lib/mutant/mutator/registry.rb

@@ -64,7 +64,7 @@ module Mutant
       # @api private
       #
       def self.assert_valid_type(type)
-        unless NODE_TYPES.include?(type) || type.kind_of?(Class)
+        unless AST::Types::ALL.include?(type) || type.kind_of?(Class)
           raise InvalidTypeError, "invalid type registration: #{type}"
         end
       end

lib/mutant/node_helpers.rb

@@ -1,52 +0,0 @@
-module Mutant
-  # Mixin for node helpers
-  module NodeHelpers
-
-    # Build node
-    #
-    # @param [Symbol] type
-    #
-    # @return [Parser::AST::Node]
-    #
-    # @api private
-    #
-    def s(type, *children)
-      Parser::AST::Node.new(type, children)
-    end
-    module_function :s
-
-    N_NAN               = s(:send, s(:float,  0.0), :/, s(:float, 0.0))
-    N_INFINITY          = s(:send, s(:float,  1.0), :/, s(:float, 0.0))
-    N_NEGATIVE_INFINITY = s(:send, s(:float, -1.0), :/, s(:float, 0.0))
-    N_RAISE             = s(:send, nil, :raise)
-    N_TRUE              = s(:true)
-    N_FALSE             = s(:false)
-    N_NIL               = s(:nil)
-    N_EMPTY             = s(:empty)
-    N_SELF              = s(:self)
-
-    # Build a negated boolean node
-    #
-    # @param [Parser::AST::Node] node
-    #
-    # @return [Parser::AST::Node]
-    #
-    # @api private
-    #
-    def n_not(node)
-      s(:send, node, :!)
-    end
-
-    NODE_TYPES.each do |type|
-      fail "method: #{type} is already defined" if instance_methods(true).include?(type)
-
-      name = "n_#{type.to_s.sub(/\??\z/, '?')}"
-
-      define_method(name) do |node|
-        node.type.equal?(type)
-      end
-      private name
-    end
-
-  end # NodeHelpers
-end # Mutant

lib/mutant/subject/method/instance.rb

@@ -39,7 +39,7 @@ module Mutant
 
         # Mutator for memoized instance methods
         class Memoized < self
-          include NodeHelpers
+          include AST::Sexp
 
           # Return source
           #

lib/mutant/zombifier/file.rb

@@ -2,7 +2,7 @@ module Mutant
   class Zombifier
     # File containing source beeing zombified
     class File
-      include NodeHelpers, Adamantium::Flat, Concord::Public.new(:path)
+      include Adamantium::Flat, Concord::Public.new(:path), AST::Sexp
 
       # Zombify contents of file
       #

meta/or_asgn.rb

@@ -22,3 +22,14 @@ Mutant::Meta::Example.add do
   mutation '@a ||= -1'
   mutation '@a ||= 2'
 end
+
+Mutant::Meta::Example.add do
+  source 'foo[:bar] ||= 1'
+
+  singleton_mutations
+  mutation 'foo[:bar] ||= nil'
+  mutation 'foo[:bar] ||= self'
+  mutation 'foo[:bar] ||= 0'
+  mutation 'foo[:bar] ||= -1'
+  mutation 'foo[:bar] ||= 2'
+end

meta/send.rb

@@ -259,7 +259,7 @@ Mutant::Meta::Example.add do
   mutation 'self[*bar]'
 end
 
-(Mutant::BINARY_METHOD_OPERATORS - [:==, :eql?]).each do |operator|
+(Mutant::AST::Types::BINARY_METHOD_OPERATORS - [:==, :eql?]).each do |operator|
   Mutant::Meta::Example.add do
     source "true #{operator} false"
 

spec/integration/mutant/test_mutator_handles_types_spec.rb

@@ -3,8 +3,8 @@ require 'spec_helper'
 describe do
 
   specify 'mutant should not crash for any node parser can generate' do
-    Mutant::NODE_TYPES.each do |type|
-      Mutant::Mutator::Registry.lookup(Mutant::NodeHelpers.s(type))
+    Mutant::AST::Types::ALL.each do |type|
+      Mutant::Mutator::Registry.lookup(s(type))
     end
   end
 end

spec/spec_helper.rb

@@ -46,7 +46,8 @@ end
 RSpec.configure do |config|
   config.include(CompressHelper)
   config.include(ParserHelper)
-  config.include(Mutant::NodeHelpers)
+  config.include(Mutant::AST::Sexp)
+
   config.expect_with :rspec do |rspec|
     rspec.syntax = :expect
   end

spec/unit/mutant/mutation_spec.rb

@@ -6,7 +6,7 @@ describe Mutant::Mutation do
     SYMBOL = 'test'.freeze
   end
 
-  let(:object)           { TestMutation.new(mutation_subject, Mutant::NodeHelpers::N_NIL)   }
+  let(:object)           { TestMutation.new(mutation_subject, Mutant::AST::Nodes::N_NIL)    }
   let(:mutation_subject) { double('Subject', identification: 'subject', source: 'original') }
   let(:node)             { double('Node')                                                   }
 

spec/unit/mutant/subject/method/instance_spec.rb

@@ -3,8 +3,6 @@
 require 'spec_helper'
 
 describe Mutant::Subject::Method::Instance do
-  include Mutant::NodeHelpers
-
   let(:object)  { described_class.new(context, node) }
   let(:context) { double }
 
@@ -73,8 +71,6 @@ describe Mutant::Subject::Method::Instance do
 end
 
 describe Mutant::Subject::Method::Instance::Memoized do
-  include Mutant::NodeHelpers
-
   let(:object)  { described_class.new(context, node) }
   let(:context) { double }
 

spec/unit/mutant/subject/method/singleton_spec.rb

@@ -3,7 +3,6 @@
 require 'spec_helper'
 
 describe Mutant::Subject::Method::Singleton do
-  include Mutant::NodeHelpers
 
   let(:object)  { described_class.new(context, node) }
   let(:context) { double }