Title: [174193] trunk/Source/WTF
- Revision
- 174193
- Author
- cdu...@apple.com
- Date
- 2014-10-01 18:18:46 -0700 (Wed, 01 Oct 2014)
Log Message
Fail better when is<>() / downcast<>() is used for an unsupported type
https://bugs.webkit.org/show_bug.cgi?id=137323
Reviewed by Benjamin Poulain.
We should fail better when is<>() / downcast<>() is used for an
unsupported type (i.e. a type that doesn't have the needed
TypeCastTraits template specialization). Previously, we would get an
obscure linking error, which was sub-optimal.
With this patch, you would now hit a static_assert() at build time if
you tried to use is<>() / downcast<>() for a type that did not have the
needed template specialization. There is also a helpful comment above
the assertion letting the developer know how to add the needed template
specialization.
* wtf/TypeCasts.h:
(WTF::TypeCastTraits::isOfType):
Modified Paths
Diff
Modified: trunk/Source/WTF/ChangeLog (174192 => 174193)
--- trunk/Source/WTF/ChangeLog 2014-10-02 00:58:35 UTC (rev 174192)
+++ trunk/Source/WTF/ChangeLog 2014-10-02 01:18:46 UTC (rev 174193)
@@ -1,3 +1,24 @@
+2014-10-01 Christophe Dumez <cdu...@apple.com>
+
+ Fail better when is<>() / downcast<>() is used for an unsupported type
+ https://bugs.webkit.org/show_bug.cgi?id=137323
+
+ Reviewed by Benjamin Poulain.
+
+ We should fail better when is<>() / downcast<>() is used for an
+ unsupported type (i.e. a type that doesn't have the needed
+ TypeCastTraits template specialization). Previously, we would get an
+ obscure linking error, which was sub-optimal.
+
+ With this patch, you would now hit a static_assert() at build time if
+ you tried to use is<>() / downcast<>() for a type that did not have the
+ needed template specialization. There is also a helpful comment above
+ the assertion letting the developer know how to add the needed template
+ specialization.
+
+ * wtf/TypeCasts.h:
+ (WTF::TypeCastTraits::isOfType):
+
2014-10-01 Commit Queue <commit-qu...@webkit.org>
Unreviewed, rolling out r174180, r174183, and r174186.
Modified: trunk/Source/WTF/wtf/TypeCasts.h (174192 => 174193)
--- trunk/Source/WTF/wtf/TypeCasts.h 2014-10-02 00:58:35 UTC (rev 174192)
+++ trunk/Source/WTF/wtf/TypeCasts.h 2014-10-02 01:18:46 UTC (rev 174193)
@@ -26,11 +26,21 @@
#ifndef TypeCasts_h
#define TypeCasts_h
+#include <type_traits>
+
namespace WTF {
template <typename ExpectedType, typename ArgType>
struct TypeCastTraits {
- static bool isOfType(ArgType&);
+ static bool isOfType(ArgType&)
+ {
+ // If you're hitting this assertion, it is likely because you used
+ // is<>() or downcast<>() with a type that doesn't have the needed
+ // TypeCastTraits specialization. Please use the following macro
+ // to add that specialization:
+ // SPECIALIZE_TYPE_TRAITS_BEGIN() / SPECIALIZE_TYPE_TRAITS_END()
+ static_assert(std::is_void<ExpectedType>::value, "Missing TypeCastTraits specialization");
+ }
};
template <typename ExpectedType>
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