" Highlighting literate directives in C++ sources.
function! HighlightTangledFile()
  " Tangled comments only make sense in the sources and are stripped out of
  " the generated .cc file. They're highlighted same as regular comments.
  syntax match tangledComment /\/\/:.*/ | highlight link tangledComment Comment
  syntax match tangledSalientComment /\/\/::.*/ | highlight link tangledSalientComment SalientComment
  set comments-=://
  set comments-=n://
  set comments+=n://:,n://

  " Inside tangle scenarios.
  syntax region tangleDirective start=+:(+ skip=+".*"+ end=+)+
  highlight link tangleDirective Delimiter
  syntax match traceContains /^+.*/
  highlight traceContains ctermfg=22
  syntax match traceAbsent /^-.*/
  highlight traceAbsent ctermfg=darkred
  syntax match tangleScenarioSetup /^\s*% .*/ | highlight link tangleScenarioSetup SpecialChar
  highlight Special ctermfg=160
endfunction
augroup LocalVimrc
  autocmd BufRead,BufNewFile *.cc call HighlightTangledFile()
  autocmd BufRead,BufNewFile *.mu set ft=mu
augroup END

" Scenarios considered:
"   opening or starting vim with a new or existing file without an extension (should interpret as C++)
"   opening or starting vim with a new or existing file with a .mu extension
"   starting vim or opening a buffer without a file name (ok to do nothing)
"   opening a second file in a new or existing window (shouldn't mess up existing highlighting)
"   reloading an existing file (shouldn't mess up existing highlighting)