`class`/`module` expression with empty body should return `nil`

Before:

  p(class A end)          #=> A
  p(class << self; end)   #=> #<Class:#<Object:0x7fdc3880e420>>
  p(module B end)         #=> B

After/Ruby:

  p(class A end)          #=> nil
  p(class << self; end)   #=> nil
  p(module B end)         #=> nil

1 files changed, 9 insertions, 0 deletions

diff --git a/test/t/module.rb b/test/t/module.rb
index 78cb5d07f..f01245e88 100644
--- a/test/t/module.rb
+++ b/test/t/module.rb
@@ -708,6 +708,15 @@ assert('module with non-class/module outer raises TypeError') do
   assert_raise(TypeError) { module []::M2 end }
 end
 
+assert('module to return the last value') do
+  m = module M; :m end
+  assert_equal(m, :m)
+end
+
+assert('module to return nil if body is empty') do
+  assert_nil(module M end)
+end
+
 assert('get constant of parent module in singleton class; issue #3568') do
   actual = module GetConstantInSingletonTest
     EXPECTED = "value"