VS 2013 originally claimed to support initializer lists but a bug was
found in which it generated bad code silently. For this reason we
previously considered support to not be present. However, Update 3 adds
a hard error on cases that previously generated bad code, so it is now
safe to use initializer lists with VS 2013 Update 3 or greater. At
worst a compiler error will be issued in the cases that do not work, but
that is no different from any other compiler-specific workaround a
project code may need.
The only reason this failed to compile on VS 2013 was because the
compiler uses different initializer_list constructor argument types than
our dummy implementation. The standard does not specify the non-default
constructor argument types for initializer_list. Use a template to
match any two-arg constructor a compiler might select (e.g. begin/end or
begin/len). Use #error to preserve the error on VS 2013.