Assert that ComputedStyleBase is only templated with ComputedStyle

third_party/WebKit/Source/build/scripts/templates/ComputedStyleBase.h.tmpl

Index: third_party/WebKit/Source/build/scripts/templates/ComputedStyleBase.h.tmpl
diff --git a/third_party/WebKit/Source/build/scripts/templates/ComputedStyleBase.h.tmpl b/third_party/WebKit/Source/build/scripts/templates/ComputedStyleBase.h.tmpl
index cf15c37253a59730ff69800aec585d3adb73bf95..61387a99796037eeb86a72c4ed05546739249020 100644
--- a/third_party/WebKit/Source/build/scripts/templates/ComputedStyleBase.h.tmpl
+++ b/third_party/WebKit/Source/build/scripts/templates/ComputedStyleBase.h.tmpl
@@ -152,6 +152,7 @@ class CORE_EXPORT ComputedStyleBase {
   {{field_templates[field.field_template].decl_public_methods(field)|indent(2)}}
 
   {% endfor %}
+

[shend, 2017/05/23 22:22:48]

nit: don't need extra space.

[nainar, 2017/05/23 23:45:16]

Done

  private:
   {% for subgroup in computed_style.subgroups %}
   {{define_field_group_class(subgroup)|indent(2)}}
@@ -169,6 +170,9 @@ class CORE_EXPORT ComputedStyleBase {
     {% for subgroup in computed_style.subgroups %}
     {{subgroup.member_name}}.Init();
     {% endfor %}
+
+    static_assert(std::is_same<ComputedStyle, ComputedStyleFinal>::value, "ComputedStyleBase can only be templated with ComputedStyle");

[shend, 2017/05/23 22:22:47]

nit: I would move this closer to the top of the class e.g.

template <class T>
class ComputedStyle : public ComputedStyleBase {
  static_assert(...);
};

also wow what magic is this? how does it even know what ComputedStyle is...

[nainar, 2017/05/23 23:45:16]

Done. Since we talked about this IRL. One of the classes imported by
ComputedStyleBase has a forward declaration of ComputedStyle. Makes this build
and work.

+
   }
 
   {% for field in computed_style.all_fields %}