Remove always dead mutations on rescue matchers

lib/mutant/mutator/node/resbody.rb

@@ -8,7 +8,7 @@ module Mutant
 
         handle(:resbody)
 
-        children :captures, :assignment, :block
+        children :captures, :assignment, :body
 
       private
 
@@ -20,7 +20,7 @@ module Mutant
         #
         def dispatch
           emit_assignment(nil)
-          emit_block_mutations if block
+          emit_body_mutations if body
           mutate_captures
         end
 
@@ -32,9 +32,8 @@ module Mutant
         #
         def mutate_captures
           return unless captures
-          emit_captures(nil)
           Util::Array.each(captures.children, self) do |matchers|
-            next if matchers.empty?
+            next if matchers.empty? || matchers.any? { |node| node.type == :nil }
             emit_captures(s(:array, *matchers))
           end
         end

spec/support/mutation_verifier.rb

@@ -46,7 +46,7 @@ private
   # @api private
   #
   def mutation_report
-    message = ['Original:', original_node.inspect]
+    message = ['Original-AST:', original_node.inspect, 'Original-Source:', Unparser.unparse(original_node)]
     if missing.any?
       message << 'Missing mutations:'
       message << missing.map(&method(:format_mutation)).join("\n-----\n")

spec/unit/mutant/mutator/node/rescue_spec.rb

@@ -10,31 +10,25 @@ describe Mutant::Mutator::Node::Generic, 'rescue' do
     let(:mutations) do
       mutations = []
       mutations << 'nil'
-      # mutations << 'begin; rescue ExceptionA, ExceptionB => error; true; end'
       mutations << 'begin; rescue ExceptionA, ExceptionB; true; end'
       mutations << 'begin; rescue ExceptionA, ExceptionB => error; false; end'
       mutations << 'begin; rescue ExceptionA, ExceptionB => error; nil; end'
-      mutations << 'begin; rescue ExceptionA, nil => error; true; end'
       mutations << 'begin; rescue ExceptionA => error; true; end'
       mutations << 'begin; rescue ExceptionB => error; true; end'
-      mutations << 'begin; rescue nil, ExceptionB => error; true; end'
-      mutations << 'begin; rescue => error; true; end'
     end
 
     it_should_behave_like 'a mutator'
   end
 
   context 'single exception selector and assignment' do
-    let(:source) { 'begin; rescue Exception => error; true; end' }
+    let(:source) { 'begin; rescue SomeException => error; true; end' }
 
     let(:mutations) do
       mutations = []
       mutations << 'nil'
-      mutations << 'begin; rescue Exception; true; end'
-      mutations << 'begin; rescue Exception => error; false; end'
-      mutations << 'begin; rescue Exception => error; nil; end'
-      mutations << 'begin; rescue nil => error; true; end'
-      mutations << 'begin; rescue => error; true; end'
+      mutations << 'begin; rescue SomeException; true; end'
+      mutations << 'begin; rescue SomeException => error; false; end'
+      mutations << 'begin; rescue SomeException => error; nil; end'
     end
 
     it_should_behave_like 'a mutator'