brew install r error

gistfile1.txt

➜  ~  brew install R
==> Using Homebrew-provided fortran compiler.
This may be changed by setting the FC environment variable.
==> Downloading http://cran.rstudio.com/src/base/R-3/R-3.1.0.tar.gz
Already downloaded: /Library/Caches/Homebrew/r-3.1.0.tar.gz
Error: undefined method `[]' for Formula:Class
Please report this bug:
    https://github.com/Homebrew/homebrew/wiki/troubleshooting
/usr/local/Library/Formula/r.rb:36:in `install'
/usr/local/Library/Homebrew/build.rb:165:in `install'
/usr/local/Library/Homebrew/formula.rb:272:in `brew'
/usr/local/Library/Homebrew/formula.rb:617:in `stage'
/usr/local/Library/Homebrew/resource.rb:63:in `unpack'
/usr/local/Library/Homebrew/extend/fileutils.rb:21:in `mktemp'
/usr/local/Library/Homebrew/resource.rb:60:in `unpack'
/usr/local/Library/Homebrew/resource.rb:53:in `stage'
/usr/local/Library/Homebrew/formula.rb:615:in `stage'
/usr/local/Library/Homebrew/formula.rb:267:in `brew'
/usr/local/Library/Homebrew/build.rb:144:in `install'
/usr/local/Library/Homebrew/build.rb:45:in `main'
/usr/local/Library/Homebrew/build.rb:12
/usr/local/Library/Formula/r.rb:82