Symbol.all_symbols was adopted by Ruby 1.8.0 or later

Author: aycabta

lib/irb/completion.rb

@@ -97,17 +97,13 @@ def self.retrieve_completion_data(input, bind: IRB.conf[:MAIN_CONTEXT].workspace
       when /^(:[^:.]*)$/
         # Symbol
         return nil if doc_namespace
-        if Symbol.respond_to?(:all_symbols)
-          sym = $1
-          candidates = Symbol.all_symbols.collect do |s|
-            ":" + s.id2name.encode(Encoding.default_external)
-          rescue Encoding::UndefinedConversionError
-            # ignore
-          end
-          candidates.grep(/^#{Regexp.quote(sym)}/)
-        else
-          []
+        sym = $1
+        candidates = Symbol.all_symbols.collect do |s|
+          ":" + s.id2name.encode(Encoding.default_external)
+        rescue Encoding::UndefinedConversionError
+          # ignore
         end
+        candidates.grep(/^#{Regexp.quote(sym)}/)
 
       when /^::([A-Z][^:\.\(]*)$/
         # Absolute Constant or class methods