Fix index assignment mutations

Changelog.md

@@ -1,5 +1,6 @@
 # v0.5.20 2014-06-xx
 
+* Readd mutation of index assignments
 * Remove a bunch of useless mutations to nil.something
 * Readd mutation of index reference arguments
 

lib/mutant/mutator/node/send.rb

@@ -35,8 +35,7 @@ module Mutant
         #
         def dispatch
           emit_singletons
-          case selector
-          when INDEX_ASSIGN
+          if selector.equal?(INDEX_ASSIGN)
             run(Index::Assign)
           else
             non_index_dispatch

lib/mutant/mutator/node/send/index.rb

@@ -10,6 +10,12 @@ module Mutant
           # Mutator for index assignments
           class Assign < self
 
+            define_named_child(:value, -1)
+
+            INDEX_RANGE = (2..-2).freeze
+
+          private
+
             # Perform dispatch
             #
             # @return [undefined]
@@ -17,7 +23,34 @@ module Mutant
             # @api private
             #
             def dispatch
-              emit(receiver)
+              emit_naked_receiver
+              emit_value_mutations
+              emit_index_read
+              emit(value)
+              mutate_indices
+            end
+
+            # Mutate indices
+            #
+            # @return [undefined]
+            #
+            # @api private
+            #
+            def mutate_indices
+              INDEX_RANGE.begin.upto(children.length + INDEX_RANGE.end).each do |index|
+                delete_child(index)
+                mutate_child(index)
+              end
+            end
+
+            # Emit index read
+            #
+            # @return [undefined]
+            #
+            # @api private
+            #
+            def emit_index_read
+              emit_type(receiver, :[], *children[INDEX_RANGE])
             end
 
           end # Assign

meta/send.rb

@@ -90,10 +90,17 @@ Mutant::Meta::Example.add do
 end
 
 Mutant::Meta::Example.add do
-  source 'foo[bar]=baz'
+  source 'foo[bar] = baz'
 
   singleton_mutations
   mutation 'foo'
+  mutation 'foo[bar]'
+  mutation 'foo[bar] = self'
+  mutation 'foo[bar] = nil'
+  mutation 'foo[nil] = baz'
+  mutation 'foo[self] = baz'
+  mutation 'foo[] = baz'
+  mutation 'baz'
 end
 
 Mutant::Meta::Example.add do