Missing support for .hs files

[haskellstudio]

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Main.hs file content is module Main where

main :: IO () main = do putStrLn "hello world"

[haskellstudio]

use vs2017, when drag hs file to vs2017, highlight works well. but when i open an folder(vs2017 new function which vs2015 vs2013 do not have) , and open an hs through solution explorer , the highlight don't wrok!