Comment # 22 on bug 1164454 from Aaron Puchert

(In reply to Stefan Weiberg from comment #21)
> I would really like to avoid putting a big version update of rust (1.36 to
> 1.40) into SLE after we are just now releasing RC1. General rule is that
> during RC Phase we are only accepting P1 fixes and nasty P2 fixes into the
> product.
> 
> Could we instead use the sources we have in SLE right now and apply the spec
> changes to let it build with llvm9?

That's not so easy, the rust guys usually have to put in quite a bit of work to
keep up with the API churn between major LLVM releases, see for example this PR
for LLVM 9 support: https://github.com/rust-lang/rust/pull/62474. That's in
rust 1.38 earliest, if I read GitHub correctly, so you'd have to port that
back.

That's why I proposed to change rust to use llvm7-devel but otherwise update to
LLVM 9 as default.

On the other hand rust developers love to live on the bleeding edge, so maybe
they'd actually appreciate the update? I don't know.