[clang] [clang-tools-extra] [lldb] [clang] Reland: fix getTemplateInstantiationArgs (PR #208601)

[Hans Wennborg via cfe-commits]

zmodem wrote:

> As far as I know, all repros could have been reproduced on the first landing, and this could have gone a lot smoother if people didn't revert so fast, or if they did, if they actually provided repros the first time around.

A different perspective is that perhaps this would have gone smoother if the patch had been tested more proactively before landing.

It seems to me that all reverts have been within the spirit of https://llvm.org/docs/DeveloperPolicy.html#patch-reversion-policy which encourages reverting *early* and investigating (including providing repros) afterwards.

>  I think this is too high risk by now to try to get in before the branch date.

Given that the branch date is tomorrow and this is the most disruptive Clang change this year, strong +1.

https://github.com/llvm/llvm-project/pull/208601