1 files changed, 43 insertions, 29 deletions
diff --git a/dom/canvas/WebGLIpdl.h b/dom/canvas/WebGLIpdl.h
index 5a35c05909..45a5c5ad64 100644
--- a/dom/canvas/WebGLIpdl.h
+++ b/dom/canvas/WebGLIpdl.h
@@ -245,6 +245,45 @@ struct ParamTraits<mozilla::dom::PredefinedColorSpace> final
           mozilla::dom::PredefinedColorSpace> {};
 
 // -
+// ParamTraits_IsEnumCase
+
+/*
+`IsEnumCase(T) -> bool` guarantees that we never have false negatives or false
+positives due to adding or removing enum cases to enums, and forgetting to
+update their serializations. Also, it allows enums to be non-continguous, unlike
+ContiguousEnumSerializer.
+*/
+
+template <class T>
+struct ParamTraits_IsEnumCase {
+  static bool Write(MessageWriter* const writer, const T& in) {
+    MOZ_ASSERT(IsEnumCase(in));
+    const auto shadow = static_cast<std::underlying_type_t<T>>(in);
+    WriteParam(writer, shadow);
+    return true;
+  }
+
+  static bool Read(MessageReader* const reader, T* const out) {
+    auto shadow = std::underlying_type_t<T>{};
+    if (!ReadParam(reader, &shadow)) return false;
+    const auto e = mozilla::AsValidEnum<T>(shadow);
+    if (!e) return false;
+    *out = *e;
+    return true;
+  }
+};
+
+// -
+
+#define USE_IS_ENUM_CASE(T) \
+  template <>               \
+  struct ParamTraits<T> : public ParamTraits_IsEnumCase<T> {};
+
+USE_IS_ENUM_CASE(mozilla::webgl::OptionalRenderableFormatBits)
+
+#undef USE_IS_ENUM_CASE
+
+// -
 // ParamTraits_TiedFields
 
 template <class T>
@@ -272,6 +311,10 @@ struct ParamTraits_TiedFields {
   }
 };
 
+template <class U, size_t N>
+struct ParamTraits<mozilla::PaddingField<U, N>> final
+    : public ParamTraits_TiedFields<mozilla::PaddingField<U, N>> {};
+
 // -
 
 template <>
@@ -609,35 +652,6 @@ struct ParamTraits<mozilla::avec3<U>> final {
   }
 };
 
-// -
-
-template <class TT>
-struct ParamTraits_IsEnumCase {
-  using T = TT;
-
-  static void Write(IPC::MessageWriter* const writer, const T& in) {
-    MOZ_RELEASE_ASSERT(IsEnumCase(in));
-    WriteParam(writer, mozilla::UnderlyingValue(in));
-  }
-
-  static bool Read(IPC::MessageReader* const reader, T* const out) {
-    std::underlying_type_t<T> rawVal;
-    if (!ReadParam(reader, &rawVal)) return false;
-    *out = static_cast<T>(rawVal);
-    return IsEnumCase(*out);
-  }
-};
-
-// -
-
-#define USE_IS_ENUM_CASE(T) \
-  template <>               \
-  struct ParamTraits<T> : public ParamTraits_IsEnumCase<T> {};
-
-USE_IS_ENUM_CASE(mozilla::webgl::OptionalRenderableFormatBits)
-
-#undef USE_IS_ENUM_CASE
-
 }  // namespace IPC
 
 #endif