Add named capture to non-capturing group mutation

- Mutate named capture groups to passive groups: `/(?<foo>bar)/` -> `/(?:bar)/`.

Changelog.md

@@ -1,5 +1,9 @@
 # Unreleased
 
+* [#1194](https://github.com/mbj/mutant/pull/1194)
+
+  * Add mutation from named capturing group to non-capturing group:  `/(?<foo>bar)/` -> `/(?:bar)`.
+
 * [#1189](https://github.com/mbj/mutant/pull/1189)
 
   * Add mutation from `=~` -> `#match?`

lib/mutant.rb

@@ -89,6 +89,7 @@ module Mutant
 require 'mutant/mutator/node/regexp'
 require 'mutant/mutator/node/regexp/alternation_meta'
 require 'mutant/mutator/node/regexp/capture_group'
+require 'mutant/mutator/node/regexp/named_group'
 require 'mutant/mutator/node/regexp/character_type'
 require 'mutant/mutator/node/regexp/end_of_line_anchor'
 require 'mutant/mutator/node/regexp/end_of_string_or_before_end_of_line_anchor'

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

@@ -0,0 +1,25 @@
+# frozen_string_literal: true
+
+module Mutant
+  class Mutator
+    class Node
+      module Regexp
+        # Mutator for regexp named capture groups, such as `/(?<foo>bar)/`
+        class NamedGroup < Node
+          handle(:regexp_named_group)
+
+          children :name, :group
+
+        private
+
+          def dispatch
+            return unless group
+
+            emit(s(:regexp_passive_group, group))
+            emit_group_mutations
+          end
+        end # EndOfLineAnchor
+      end # Regexp
+    end # Node
+  end # Mutator
+end # Mutant

meta/regexp.rb

@@ -93,6 +93,7 @@
   singleton_mutations
   mutation '//'
   mutation '/nomatch\A/'
+  mutation '/(?:.)/'
 end
 
 Pathname

meta/regexp/regexp_named_group.rb

@@ -0,0 +1,18 @@
+# frozen_string_literal: true
+
+Mutant::Meta::Example.add :regexp_named_group do
+  source '/(?<foo>)/'
+
+  singleton_mutations
+  regexp_mutations
+end
+
+Mutant::Meta::Example.add :regexp_named_group do
+  source '/(?<foo>\w)/'
+
+  singleton_mutations
+  regexp_mutations
+
+  mutation '/(?:\w)/'
+  mutation '/(?<foo>\W)/'
+end