Chandler Carruth 238121e8d2 [ADT] Add a generic concatenating iterator and range (take 2).
This recommits r290512 that was reverted when MSVC failed to compile it. Since
then I've played with various approaches using rextester.com (where I was able
to reproduce the failure) and think that I have a solution thanks in part to
the help of Dave Blaikie! It seems MSVC just has a defective `decltype` in this
version. Manually writing out the type seems to do the trick, even though it is
.... quite complicated.

Original commit message:
This allows both defining convenience iterator/range accessors on types
which walk across N different independent ranges within the object, and
more direct and simple usages with range based for loops such as shown
in the unittest. The same facilities are used for both. They end up
quite small and simple as it happens.

I've also switched an iterator on `Module` to use this. I would like to
add another convenience iterator that includes even more sequences as
part of it and seeing this one already present motivated me to actually
abstract it away and introduce a general utility.

Differential Revision: https://reviews.llvm.org/D28093

llvm-svn: 290528
2016-12-25 23:41:14 +00:00
..