lines_cop: Fix detection of negated expression

Library/Homebrew/rubocops/extend/formula_cop.rb

@@ -316,8 +316,10 @@ module RuboCop
       end
 
       # Check if negation is present in the given node
-      def negated?(node)
-        method_called?(node, :!)
+      def expression_negated?(node)
+        return false if node.parent.nil?
+        return false unless node.parent.method_name.equal?(:!)
+        offending_node(node.parent)
       end
 
       # Return all the caveats' string nodes in an array

Library/Homebrew/rubocops/lines_cop.rb

@@ -94,12 +94,12 @@ module RuboCop
           end
 
           find_instance_method_call(body_node, :build, :with?) do |method|
-            next unless negated?(method.parent)
+            next unless expression_negated?(method)
             problem "Don't negate 'build.with?': use 'build.without?'"
           end
 
           find_instance_method_call(body_node, :build, :without?) do |method|
-            next unless negated?(method.parent)
+            next unless expression_negated?(method)
             problem "Don't negate 'build.without?': use 'build.with?'"
           end