Fix removing ivars from clases and modules.

Co-authored-by: Adam Hess <hparker@github.com>

shape.c

@@ -238,7 +238,9 @@ remove_shape_recursive(VALUE obj, ID id, rb_shape_t * shape, VALUE * removed)
             // has the same attributes as this shape.
             if (new_parent) {
                 bool dont_care;
-                rb_shape_t * new_child = get_next_shape_internal(new_parent, shape->edge_name, shape->type, &dont_care, true, false);
+                enum ruby_value_type type = BUILTIN_TYPE(obj);
+                bool new_shape_necessary = type == T_CLASS || type == T_MODULE;
+                rb_shape_t * new_child = get_next_shape_internal(new_parent, shape->edge_name, shape->type, &dont_care, true, new_shape_necessary);
                 new_child->capacity = shape->capacity;
                 if (new_child->type == SHAPE_IVAR) {
                     move_iv(obj, id, shape->next_iv_index - 1, new_child->next_iv_index - 1);

test/ruby/test_shapes.rb

@@ -108,6 +108,32 @@ def test_too_many_ivs_on_class
     assert_false RubyVM::Shape.of(obj).too_complex?
   end
 
+  def test_removing_when_too_many_ivs_on_class
+    obj = Class.new
+
+    (RubyVM::Shape::SHAPE_MAX_NUM_IVS + 2).times do
+      obj.instance_variable_set(:"@a#{_1}", 1)
+    end
+    (RubyVM::Shape::SHAPE_MAX_NUM_IVS + 2).times do
+      obj.remove_instance_variable(:"@a#{_1}")
+    end
+
+    assert_empty obj.instance_variables
+  end
+
+  def test_removing_when_too_many_ivs_on_module
+    obj = Module.new
+
+    (RubyVM::Shape::SHAPE_MAX_NUM_IVS + 2).times do
+      obj.instance_variable_set(:"@a#{_1}", 1)
+    end
+    (RubyVM::Shape::SHAPE_MAX_NUM_IVS + 2).times do
+      obj.remove_instance_variable(:"@a#{_1}")
+    end
+
+    assert_empty obj.instance_variables
+  end
+
   def test_too_complex_ractor
     assert_separately([], "#{<<~"begin;"}\n#{<<~'end;'}")
     begin;