Add character type mutations

Mutations:

  - `/\b/` -> `/\B/` (closes #577)
  - `/\B/` -> `/\b/` (closes #578)
  - `/\d/` -> `/\D/` (closes #579)
  - `/\D/` -> `/\d/` (closes #580)
  - `/\s/` -> `/\S/` (closes #583)
  - `/\S/` -> `/\s/` (closes #584)
  - `/\w/` -> `/\W/` (closes #585)
  - `/\W/` -> `/\w/` (closes #586)

config/flay.yml

@@ -1,3 +1,3 @@
 ---
 threshold: 16
-total_score: 1290
+total_score: 1317

lib/mutant.rb

@@ -91,6 +91,7 @@ require 'mutant/mutator/util/symbol'
 require 'mutant/mutator/node'
 require 'mutant/mutator/node/generic'
 require 'mutant/mutator/node/regexp'
+require 'mutant/mutator/node/regexp/character_type'
 require 'mutant/mutator/node/literal'
 require 'mutant/mutator/node/literal/boolean'
 require 'mutant/mutator/node/literal/range'

lib/mutant/mutator/node/generic.rb

@@ -39,6 +39,14 @@ module Mutant
         unsupported_regexp_nodes = AST::Types::REGEXP.to_a - %i[
           regexp_root_expression
           regexp_bol_anchor
+          regexp_word_type
+          regexp_nonword_type
+          regexp_digit_type
+          regexp_nondigit_type
+          regexp_space_type
+          regexp_nonspace_type
+          regexp_word_boundary_anchor
+          regexp_nonword_boundary_anchor
         ]
 
         # These nodes still need a dedicated mutator,

lib/mutant/mutator/node/regexp/character_type.rb

@@ -0,0 +1,28 @@
+module Mutant
+  class Mutator
+    class Node
+      module Regexp
+        # Character type mutator
+        class CharacterType < Node
+          map = {
+            regexp_word_type:            :regexp_nonword_type,
+            regexp_digit_type:           :regexp_nondigit_type,
+            regexp_space_type:           :regexp_nonspace_type,
+            regexp_word_boundary_anchor: :regexp_nonword_boundary_anchor
+          }
+
+          MAP = IceNine.deep_freeze(map.merge(map.invert))
+
+          handle(*MAP.keys)
+
+          # Mutate to invert character type
+          #
+          # @return [undefined]
+          def dispatch
+            emit(s(MAP.fetch(node.type)))
+          end
+        end # CharacterType
+      end # Regexp
+    end # Node
+  end # Mutator
+end # Mutant

meta/regexp/character_types.rb

@@ -0,0 +1,19 @@
+mutations = {
+  [:regexp_word_type,            '/\w/'] => [:regexp_nonword_type,            '/\W/'],
+  [:regexp_digit_type,           '/\d/'] => [:regexp_nondigit_type,           '/\D/'],
+  [:regexp_space_type,           '/\s/'] => [:regexp_nonspace_type,           '/\S/'],
+  [:regexp_word_boundary_anchor, '/\b/'] => [:regexp_nonword_boundary_anchor, '/\B/']
+}
+
+mutations = mutations.merge(mutations.invert)
+
+mutations.each do |(source_type, source_mutation), (_, regexp_mutation)|
+  Mutant::Meta::Example.add source_type do
+    source(source_mutation)
+
+    singleton_mutations
+    regexp_mutations
+
+    mutation(regexp_mutation)
+  end
+end