module CodeRay::FileType

def [] filename, read_shebang = false

That means you can get filetypes from files that don't exist.
The file itself is only accessed when +read_shebang+ is set to true.

+filename+ is a relative or absolute path to a file.

Try to determine the file type of the file. 
def [] filename, read_shebang = false
  name = File.basename filename
  ext = File.extname(name).sub(/^\./, '')  # from last dot, delete the leading dot
  ext2 = filename.to_s[/\.(.*)/, 1]  # from first dot
  
  type =
    TypeFromExt[ext] ||
    TypeFromExt[ext.downcase] ||
    (TypeFromExt[ext2] if ext2) ||
    (TypeFromExt[ext2.downcase] if ext2) ||
    TypeFromName[name] ||
    TypeFromName[name.downcase]
  type ||= shebang(filename) if read_shebang
  
  type
end