cannot install llvm using homebrew on macOS mojave - homebrew

Question

System: macOS mojave 10.14.6
when I use brew install llvm, this error appears:
Error: cmake: undefined method `on_linux' for #<Class:0x00007f7f744bf6b8>

Answer 1

I happened to have a Mojave machine and re-did the installation process myself, and it works fine.
Here is what I did:
brew install llvm (I actually used brew reinstall llvm, since it is reinstall for me)
echo 'export PATH="/usr/local/opt/llvm/bin:$PATH"' >> ~/.bash_profile, brew version would be on your PATH
source ~/.bash_profile, apply the PATH change
The full installation log:
$ brew reinstall llvm
==> Downloading https://homebrew.bintray.com/bottles/llvm-10.0.0_3.moj
Already downloaded: /Users/rchen/Library/Caches/Homebrew/downloads/6d4c3816f98949b64550d4a36656b2661f8e5aeea36a90abbdbea68c8215b9a2--llvm-10.0.0_3.mojave.bottle.tar.gz
==> Reinstalling llvm
==> Pouring llvm-10.0.0_3.mojave.bottle.tar.gz
==> Caveats
To use the bundled libc++ please add the following LDFLAGS:
LDFLAGS="-L/usr/local/opt/llvm/lib -Wl,-rpath,/usr/local/opt/llvm/lib"
llvm is keg-only, which means it was not symlinked into /usr/local,
because macOS already provides this software and installing another version in
parallel can cause all kinds of trouble.
If you need to have llvm first in your PATH run:
echo 'export PATH="/usr/local/opt/llvm/bin:$PATH"' >> /Users/rchen/.bash_profile
For compilers to find llvm you may need to set:
export LDFLAGS="-L/usr/local/opt/llvm/lib"
export CPPFLAGS="-I/usr/local/opt/llvm/include"
==> Summary
🍺 /usr/local/Cellar/llvm/10.0.0_3: 7,055 files, 1GB
test log (after PATH change):
$ clang --version
clang version 10.0.0
Target: x86_64-apple-darwin18.7.0
Thread model: posix
InstalledDir: /usr/local/opt/llvm/bin