Use stricter type checking in UMA_HISTOGRAM_ENUMERATION

base/metrics/histogram_macros_internal.h

Index: base/metrics/histogram_macros_internal.h
diff --git a/base/metrics/histogram_macros_internal.h b/base/metrics/histogram_macros_internal.h
index c107a4729d26243d6e81d510e03fb769abb137aa..2bb0e0a39d237c5beb39a1f3cd4528cd9a89cc42 100644
--- a/base/metrics/histogram_macros_internal.h
+++ b/base/metrics/histogram_macros_internal.h
@@ -139,6 +139,12 @@
 // types.
 #define INTERNAL_HISTOGRAM_ENUMERATION_WITH_FLAG(name, sample, boundary, flag) \
   do {                                                                         \
+    static_assert(                                                             \
+        !std::is_enum<std::remove_const<std::remove_reference<decltype(        \

[dcheng, 2017/07/17 09:13:59]

I think std::decay can replace the use of
std::remove_const<std::remove_reference<...>> here and below.

+                boundary)>::type>::type>::value ||                             \
+            std::is_enum<std::remove_const<                                    \
+                std::remove_reference<decltype(sample)>::type>::type>::value,  \
+        "Unexpected: |boundary| is enum, but |sample| is not.");               \
     static_assert(                                                             \
         !std::is_enum<decltype(sample)>::value ||                              \
             !std::is_enum<decltype(boundary)>::value ||                        \