Feature 17314: alias_method returns symbol

NEWS.md

@@ -253,6 +253,9 @@ Outstanding ones only.
       methods now return array of defined methods names as symbols.
       [[Feature #17314]]
 
+    * Module#alias_method now returns the defined alias as symbol.
+      [[Feature #17314]]
+
 * Mutex
 
     * `Mutex` is now acquired per-`Fiber` instead of per-`Thread`. This change

spec/ruby/core/module/alias_method_spec.rb

@@ -85,8 +85,19 @@ describe "Module#alias_method" do
     Module.should have_public_instance_method(:alias_method, false)
   end
 
-  it "returns self" do
-    @class.send(:alias_method, :checking_return_value, :public_one).should equal(@class)
+  describe "returned value" do
+    ruby_version_is ""..."3.0" do
+      it "returns self" do
+        @class.send(:alias_method, :checking_return_value, :public_one).should equal(@class)
+      end
+    end
+
+    ruby_version_is "3.0" do
+      it "returns symbol of the defined method name" do
+        @class.send(:alias_method, :checking_return_value, :public_one).should equal(:checking_return_value)
+        @class.send(:alias_method, 'checking_return_value', :public_one).should equal(:checking_return_value)
+      end
+    end
   end
 
   it "works in module" do

vm_method.c

@@ -1941,13 +1941,13 @@ rb_alias(VALUE klass, ID alias_name, ID original_name)
 
 /*
  *  call-seq:
- *     alias_method(new_name, old_name)   -> self
+ *     alias_method(new_name, old_name)   -> symbol
  *
  *  Makes <i>new_name</i> a new copy of the method <i>old_name</i>. This can
  *  be used to retain access to methods that are overridden.
  *
  *     module Mod
- *       alias_method :orig_exit, :exit
+ *       alias_method :orig_exit, :exit #=> :orig_exit
  *       def exit(code=0)
  *         puts "Exiting with code #{code}"
  *         orig_exit(code)
@@ -1968,8 +1968,9 @@ rb_mod_alias_method(VALUE mod, VALUE newname, VALUE oldname)
     if (!oldid) {
 	rb_print_undef_str(mod, oldname);
     }
-    rb_alias(mod, rb_to_id(newname), oldid);
-    return mod;
+    VALUE id = rb_to_id(newname);
+    rb_alias(mod, id, oldid);
+    return ID2SYM(id);
 }
 
 static void