let speed bar recognize scala file perfectly

gistfile1.txt

1. create ~/.ctags as follows(notice for regexps I used ^[ \t] to excactly match):
--langdef=Scala
--langmap=Scala:.scala
--regex-Scala=/^[ \t]*class[ \t]*([a-zA-Z0-9_]+)/class \1/c,classes/
--regex-Scala=/^[ \t]*object[ \t]*([a-zA-Z0-9_]+)/object \1/o,objects/
--regex-scala=/^[ \t]*trait[ \t]*([a-zA-Z0-9_]+)/trait \1/t,traits/
--regex-Scala=/^[ \t]*case[ \t]*class[ \t]*([a-zA-Z0-9_]+)/case class \1/m,case-classes/
--regex-Scala=/^[ \t]*abstract[ \t]*class[ \t]*([a-zA-Z0-9_]+)/abstract class \1/a,abstract-classes/
--regex-Scala=/^[^\*\/]*def[ \t]*([a-zA-Z0-9_]+)[ \t]*.*[:=]/f \1/f,functions/
#--regex-Scala=/^[^\*\/]*val[ \t]*([a-zA-Z0-9_]+)[ \t]*[:=]/\1/V,values/
#--regex-Scala=/^[^\*\/]*var[ \t]*([a-zA-Z0-9_]+)[ \t]*[:=]/\1/v,variables/
#--regex-Scala=/^[^\*\/]*type[ \t]*([a-zA-Z0-9_]+)[ \t]*[\[<>=]/\1/T,types/

2.0 make sure you installed exuberant ctags (brew install ctags-exuberant)
2.1 change your emacs setting as:
(speedbar-add-supported-extension ".scala")
;(setq speedbar-use-imenu-flag nil)
(setq speedbar-fetch-etags-command "ctags")

(setq speedbar-fetch-etags-arguments '("-e" "-f -"))
(add-to-list 'speedbar-fetch-etags-parse-list
            '("\\.scala" . speedbar-parse-c-or-c++tag))

PS: notice I changed the command to ctags, that's because emacs by default uses etags to generate tag and therefore will not utlize the .ctags file we customized on step 1
3.0 enjoy