Fix remove_instance_variable for too complex class

test/ruby/test_shapes.rb

@@ -233,7 +233,7 @@ class TestShapes < Test::Unit::TestCase
     end;
   end
 
-  def test_run_out_of_shape
+  def test_run_out_of_shape_for_object
     assert_separately([], "#{<<~"begin;"}\n#{<<~'end;'}")
     begin;
       class A
@@ -252,6 +252,23 @@ class TestShapes < Test::Unit::TestCase
     end;
   end
 
+  def test_run_out_of_shape_for_class
+    assert_separately([], "#{<<~"begin;"}\n#{<<~'end;'}")
+    begin;
+      c = Class.new
+      i = 0
+      while RubyVM::Shape.shapes_available > 0
+        c.instance_variable_set(:"@i#{i}", 1)
+        i += 1
+      end
+
+      c.instance_variable_set(:@a, 1)
+      assert_equal(1, c.instance_variable_get(:@a))
+      c.remove_instance_variable(:@a)
+      assert_nil(c.instance_variable_get(:@a))
+    end;
+  end
+
   def test_run_out_of_shape_generic_ivar_set
     assert_separately([], "#{<<~"begin;"}\n#{<<~'end;'}")
     begin;

variable.c

@@ -2198,7 +2198,12 @@ rb_obj_remove_instance_variable(VALUE obj, VALUE name)
       case T_CLASS:
       case T_MODULE:
         IVAR_ACCESSOR_SHOULD_BE_MAIN_RACTOR(id);
+        if (rb_shape_obj_too_complex(obj)) {
+            st_delete(RCLASS_IV_HASH(obj), (st_data_t *)&id, (st_data_t *)&val);
+        }
+        else {
             rb_shape_transition_shape_remove_ivar(obj, id, shape, &val);
+        }
         break;
       case T_OBJECT: {
         if (rb_shape_obj_too_complex(obj)) {