gistfile1.txt

$ ./take-throw-test.hs
with
m
...
with
m
with
m
with
m
with
m
with
take-throw-test.hs: user error (take and throw)
take-throw-test.hs: thread blocked indefinitely in an MVar operation

take-throw-test.hs

#!/usr/bin/env stack
-- stack --install-ghc runghc --package exceptions

import Control.Concurrent (forkIO, threadDelay)
import Control.Concurrent.MVar (newMVar, withMVar, takeMVar)
import Control.Exception (throwIO)
import Control.Monad (forever)
import System.IO (BufferMode(LineBuffering), hSetBuffering, stdout)

main = do
  hSetBuffering stdout LineBuffering
  m <- newMVar "m"
  forkIO $ do
    threadDelay 10000
    takeMVar m
    throwIO $ userError "take and throw"
  forever $ do
    putStrLn "with"
    withMVar m putStrLn

I also tested this with a "Russian Doll" MVar and GHC still catches it

main = do
  hSetBuffering stdout LineBuffering
  n <- newMVar =<< newMVar "m"
  forkIO $ do
    threadDelay 10000

    m <- takeMVar n
    takeMVar m
    putMVar n m

    throwIO $ userError "take and throw"

  forever $ do
    putStrLn "with"
    withMVar n (`withMVar` putStrLn)