[Bug #21669] Add more void value expression check for `if`

If the both branches are void, the `if`/`unless` is also void.

1 files changed, 9 insertions, 0 deletions

diff --git a/test/ruby/test_syntax.rb b/test/ruby/test_syntax.rb
index 3638d83e2b..a64591ecec 100644
--- a/test/ruby/test_syntax.rb
+++ b/test/ruby/test_syntax.rb
@@ -2021,6 +2021,15 @@ eom
     assert_valid_syntax("tap {a = (true ? true : break)}")
     assert_valid_syntax("tap {a = (break if false)}")
     assert_valid_syntax("tap {a = (break unless true)}")
+
+    assert_syntax_error("#{<<~"{#"}\n#{<<~'};'}", /void value expression/, nil, "#{BUG_21669} 1.4")
+    {#
+      x = if rand < 0.5
+        return
+      else
+        return
+      end
+    };
   end
 
   def test_value_expr_in_singleton