Disallow cast/implicit conversion from LayoutUnit to int/unsigned

third_party/WebKit/Source/platform/LayoutUnit.h

Index: third_party/WebKit/Source/platform/LayoutUnit.h
diff --git a/third_party/WebKit/Source/platform/LayoutUnit.h b/third_party/WebKit/Source/platform/LayoutUnit.h
index 700aef96bd08df3423fe5895456321b7f03893b8..c61c1d297b64c6c29bb7c1477b504b9237d65737 100644
--- a/third_party/WebKit/Source/platform/LayoutUnit.h
+++ b/third_party/WebKit/Source/platform/LayoutUnit.h
@@ -107,8 +107,10 @@ public:
     }
     unsigned toUnsigned() const { REPORT_OVERFLOW(m_value >= 0); return toInt(); }
 
-    operator int() const { return toInt(); }
-    operator unsigned() const { return toUnsigned(); }
+    // Conversion to int or unsigned is lossy. Use toInt() and toUnsigned() instead.
+    operator int() const = delete;
+    operator unsigned() const = delete;

[Stephen Chennney, 2016/08/22 17:46:10]

Am I right that these need to be deleted because otherwise there would be a
default cast on the m_value member?

[Xianzhu, 2016/08/22 18:14:38]

Even worse. To avoid implicit lossy conversion, we could add 'explicit' to these
operators, but the compiler would try to find other implicit conversion paths
and would either report ambiguous conversion error (because of multiple paths:
operator float() then int and operator bool() then int) or generate wrong code
if it chose the operator bool() then int path.

Added comment about the reason of 'delete'.

+
     operator double() const { return toDouble(); }
     operator float() const { return toFloat(); }
     operator bool() const { return m_value; }