Output of brew install -v llvm --with-clang

gistfile1.txt

==> Downloading http://llvm.org/releases/3.1/llvm-3.1.src.tar.gz
Already downloaded: /Library/Caches/Homebrew/llvm-3.1.tar.gz
/usr/bin/tar xf /Library/Caches/Homebrew/llvm-3.1.tar.gz
Error: can't convert nil into String
Please report this bug:
    https://github.com/mxcl/homebrew/wiki/bug-fixing-checklist
/usr/local/Library/Homebrew/formula_support.rb:210:in `+'
/usr/local/Library/Homebrew/formula_support.rb:210:in `include?'
/usr/local/Library/Formula/llvm.rb:31:in `install'
/usr/local/Library/Homebrew/build.rb:102:in `install'
/usr/local/Library/Homebrew/formula.rb:214:in `brew'
/usr/local/Library/Homebrew/formula.rb:513:in `stage'
/usr/local/Library/Homebrew/extend/fileutils.rb:22:in `mktemp'
/usr/local/Library/Homebrew/formula.rb:509:in `stage'
/usr/local/Library/Homebrew/formula.rb:209:in `brew'
/usr/local/Library/Homebrew/build.rb:82:in `install'
/usr/local/Library/Homebrew/build.rb:44
/usr/local/Library/Formula/llvm.rb:86