From 7243e40e02097fbedf293b1159bf5850f4ca91ce Mon Sep 17 00:00:00 2001
From: Markus Schirp <mbj@schirp-dso.com>
Date: Sun, 29 Aug 2021 20:20:35 +0000
Subject: [PATCH] Remove useless binary left negation

[Fix #1240]

* This orthogonal is not universal, especially in assignment cases.
---
 lib/mutant/mutator/node/binary.rb |  5 -----
 meta/and.rb                       |  1 -
 meta/or.rb                        | 14 +++++++++++++-
 3 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/lib/mutant/mutator/node/binary.rb b/lib/mutant/mutator/node/binary.rb
index 3e2492bbf..202daaa58 100644
--- a/lib/mutant/mutator/node/binary.rb
+++ b/lib/mutant/mutator/node/binary.rb
@@ -21,7 +21,6 @@ def dispatch
           emit_singletons
           emit_promotions
           emit_operator_mutations
-          emit_left_negation
           emit_left_mutations
           emit_right_mutations
         end
@@ -35,10 +34,6 @@ def emit_promotions
           emit(right)
         end
 
-        def emit_left_negation
-          emit(s(node.type, n_not(left), right))
-        end
-
       end # Binary
     end # Node
   end # Mutator
diff --git a/meta/and.rb b/meta/and.rb
index 1c1ac7103..e6ea8fe19 100644
--- a/meta/and.rb
+++ b/meta/and.rb
@@ -9,5 +9,4 @@
   mutation 'true or false'
   mutation 'false and false'
   mutation 'true and true'
-  mutation '!true and false'
 end
diff --git a/meta/or.rb b/meta/or.rb
index 133777847..6827541b7 100644
--- a/meta/or.rb
+++ b/meta/or.rb
@@ -9,5 +9,17 @@
   mutation 'false or false'
   mutation 'true or true'
   mutation 'true and false'
-  mutation '!true or false'
+end
+
+Mutant::Meta::Example.add :or do
+  source 'a = true or false'
+
+  singleton_mutations
+  mutation 'false'
+  mutation 'a = true'
+  mutation 'a = false or false'
+  mutation 'a = true or true'
+  mutation 'a = true and false'
+  mutation 'nil or false'
+  mutation 'a__mutant__ = true or false'
 end