Improve compatibility for Symbol#name

Rakefile

@@ -162,7 +162,6 @@ IGNORE_IN_200 = %w[
 ]
 
 IGNORE = %w[
-  3.0.0/symbol/name
   3.0.0/ractor/ractor
   3.1.0/enumerable/compact
   3.1.0/struct/keyword_init

lib/backports/3.0.0/symbol/name.rb

@@ -1,11 +1,21 @@
 unless Symbol.method_defined? :name
-  def Backports.symbol_names
-    @symbol_names ||= ObjectSpace::WeakMap.new
-  end
+  if ((ObjectSpace::WeakMap.new[:test] = :test) rescue false)
+    # WeakMaps accept symbols only in Ruby 2.7+
+    def Backports.symbol_names
+      @symbol_names ||= ObjectSpace::WeakMap.new
+    end
 
-  class Symbol
-    def name
-      Backports.symbol_names[self] ||= to_s.freeze
+    class Symbol
+      def name
+        Backports.symbol_names[self] ||= to_s.freeze
+      end
+    end
+  else
+    # For earlier Rubies, we can't pool their strings
+    class Symbol
+      def name
+        to_s.freeze
+      end
     end
   end
 end

spec/tags/2.0.0/core/symbol/name_spec.rb

@@ -0,0 +1 @@
+fails:Symbol#name returns same string instance

spec/tags/2.1.0/core/symbol/name_spec.rb

@@ -0,0 +1 @@
+fails:Symbol#name returns same string instance

spec/tags/2.2.0/core/symbol/name_spec.rb

@@ -0,0 +1 @@
+fails:Symbol#name returns same string instance

spec/tags/2.3.0/core/symbol/name_spec.rb

@@ -0,0 +1 @@
+fails:Symbol#name returns same string instance

spec/tags/2.4.0/core/symbol/name_spec.rb

@@ -0,0 +1 @@
+fails:Symbol#name returns same string instance

spec/tags/2.5.0/core/symbol/name_spec.rb

@@ -0,0 +1 @@
+fails:Symbol#name returns same string instance

spec/tags/2.6.0/core/symbol/name_spec.rb

@@ -0,0 +1 @@
+fails:Symbol#name returns same string instance