[clang] [C++20][Modules] Load function body from the module that gives canonical decl (PR #111992)

[Chuanqi Xu via cfe-commits]

ChuanqiXu9 wrote:

@DimitryAndric given this is landed more than a year ago, maybe it is better to discuss this in a new issue. 

For reducing, I generally reduce manually. That is, I tried to find the minimal set of files which causing the crash. Then I preprocess all the files (including std headers). And I manually remove things in the preprocessed files and observe if the crash still happens. And I did this recursively to find the minimal reproducer.

@ilya-biryukov I think google has some methods to do this automatically. Could you share them? I feel it will be great if you can document your methods.

https://github.com/llvm/llvm-project/pull/111992