Comment # 5 on bug 1091551 from Michal Srb

Both llvm4 and llvm5 in devel:tools:compiler build against Leap 42.3, but they
can not be submitted to openSUSE:Leap:42.3 as-is because that project already
contains "llvm" package (llvm 3.8) which is not prepared to coexist with other
versions of LLVM. You would get file conflicts.

AFAIK rust needs only the LLVM libraries and the matching devel files for
build. Maybe we could limit the llvm4 in Leap 42.3 to packages "libLLVM4" and
"llvm4-devel" and omit all the remaining ones.