[llvm] r189495 - PR16995: DebugInfo: Don't overwrite existing member lists when adding template arguments

[Eric Christopher]

>> Perhaps take the code from the PR and verifying all of the elements
>> are there at least. It won't reproduce the bug necessarily but could
>> be a good general test.
>
> Maybe - it's a bit scattershot. It requires particularly circuitous
> references to create these cases where the expansion of context,
> template arguments, etc, causes the type itself to be expanded. The
> asserts pull these failure modes into less esoteric test cases.
>

No worries, not fussed.

>> Just a block comment above the verification code on what you're
>> verifying. I.e. something along the lines of "Iterate through the two
>> lists of elements and ensure that we've got an identical or superset
>> of elements." Comments are easier to read than the code.
>
> Pulled this out into a separate function to hopefully make the code
> more self-documenting without comments (& should make the main path
> through the code easier as you don't have to visually skip all the
> loop details, etc) in r189512.

Helped immensely. Thanks!

-eric