[cfe-dev] help wordsmithing documentation?

Nick Lewycky nlewycky at google.com
Mon Jan 20 16:36:56 PST 2014

In the documentation for
I have this paragraph:

An enable_if expression will be evaluated by substituting the values of the
> parameters from the call site into the arguments in the expression and
> determining whether the result is true. If the result is false or could not
> be determined through constant expression evaluation, then this overload
> will not be chosen and the reason supplied in the string will be given to
> the user if their code does not compile as a result.

The problem I have with this is that "evaluated by substituting" is
ambiguous. You could observe a different result if the implementation
performed template-instantiation style substitution, as opposed what we
actually do which is pretending that the expression was inside a constexpr
function being called with the parameters from the call-site.

I do mention that we perform constant expression evaluation, but it sounds
like that happens after the substitution. Is there some more precise
language I could use to clarify exactly how the extension behaves?

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