Use a refinement for Symbol#name instead of a polyfill

.rubocop.yml

@@ -13,6 +13,9 @@ AllCops:
 Layout/LineLength:
   Max: 80
 
+Lint/AmbiguousBlockAssociation:
+  Enabled: false
+
 Lint/DuplicateBranch:
   Enabled: false
 

lib/syntax_tree.rb

@@ -22,16 +22,6 @@
 
 require_relative "syntax_tree/parser"
 
-# We rely on Symbol#name being available, which is only available in Ruby 3.0+.
-# In case we're running on an older Ruby version, we polyfill it here.
-unless :+.respond_to?(:name)
-  class Symbol # rubocop:disable Style/Documentation
-    def name
-      to_s.freeze
-    end
-  end
-end
-
 # Syntax Tree is a suite of tools built on top of the internal CRuby parser. It
 # provides the ability to generate a syntax tree from source, as well as the
 # tools necessary to inspect and manipulate that syntax tree. It can be used to

lib/syntax_tree/node.rb

@@ -1651,6 +1651,20 @@ def format(q)
   #     array << value
   #
   class Binary < Node
+    # Since Binary's operator is a symbol, it's better to use the `name` method
+    # than to allocate a new string every time. This is a tiny performance
+    # optimization, but enough that it shows up in the profiler. Adding this in
+    # for older Ruby versions.
+    unless :+.respond_to?(:name)
+      using Module.new {
+        refine Symbol do
+          def name
+            to_s.freeze
+          end
+        end
+      }
+    end
+
     # [untyped] the left-hand side of the expression
     attr_reader :left