Re: using enum classes for enumerated CSS property values in nsStyleConsts.h

On 11/10/2015 11:24 PM, Xidorn Quan wrote:
> On Wed, Nov 11, 2015 at 6:21 PM, Daniel Holbert <[email protected]> wrote:
>>
>> P.S. (I can work around this by adding an "operator bool" to the
>> CastableTypedEnumResult type-definition in mfbt/TypedEnumBits.h. Maybe
>> that's something we should do.)
> 
> We should just add "explicit operator bool() const;" to
> CastableTypedEnumResult, which we are allowed to use since VS2012
> support was dropped.

Cool -- though, are you sure we'd want "explicit"?

The point of my email was that *implicit* conversion to bool is
convenient & desirable (IMO) for these bitmask types, particularly when
passing them as a boolean function-argument.

I don't see too much danger from bool-conversion here, and I'd much
rather type:
  SomeFunc(foo | MyMaskType::SomeBit);

...rather than having to use explicit conversion like:
  SomeFunc(static_cast<bool>(foo | MyMaskType::SomeBit)));

If we use the "explicit" keyword, then we'd have to resort to the second
example here. (or we'd have to use "!!", or we'd have to rewrite
SomeFunc to stop taking a bool)

~Daniel