Extending Haskell syntax highlighting to allow for inline C snippets

Question

There is a Haskell program called inline-C which allows C code snippets to placed inline Haskell code, as follows:

main :: IO ()
main = do
  x <- [C.block| int {
      // Read and sum 5 integers
      int i, sum = 0, tmp;
      for (i = 0; i < 5; i++) {
        scanf("%d", &tmp);
        sum += tmp;
      }
      return sum;
    } |]
  print x

As you can see, there is a C code snippet above in between the [C.block| and |].

Is there a way to make it so that portions of code in between these are highlighted as C code?

Answer 1

You can include syntax files with syn include. Putting this in ~/.vim/after/syntax/haskell.vim seems to work fairly well:

" C syntax file won't load if this is set
unlet b:current_syntax

" Load C syntax
syn include @C syntax/c.vim

" Define a syntax region which can contain C syntax
syn region haskellC keepend
    \ start=/\v(\[C\.block\|)@<= \w+ \{/
    \ end=/} \|]/
    \ contains=@C

" Re-set the current syntax
let b:current_syntax = 'haskell'