Don't lose parantheses in show SomeAsyncException #253
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ntc2
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May 21, 2019
By implementing it using `showsPrec` instead of `show`, so that it
will optionally insert parentheses. Here's an example
import Control.Concurrent.Async
import Control.Concurrent
import Control.Exception
main :: IO ()
main = do
let oneSecond = 1000000
a <- async $ do
a <- async $ do
evaluate $ 1 `div` 0
return ()
link a
threadDelay oneSecond
wait a
link a
threadDelay oneSecond
wait a
Running this program produces
./Test
Test: ExceptionInLinkedThread ThreadId 2 ExceptionInLinkedThread ThreadId 4 divide by zero
But with the change in the current commit, and some related GHC
PRs (ghc/ghc#254,
ghc/ghc#253), it should produce
./Test
Test: ExceptionInLinkedThread (ThreadId 2) (ExceptionInLinkedThread (ThreadId 4) divide by zero)
instead.
|
Please can you open this MR on gitlab? |
|
@mpickering done: https://gitlab.haskell.org/ghc/ghc/merge_requests/1001. Sorry, I hadn't realized that trivial PRs were no longer accepted on GitHub. |
kcsongor
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Jan 7, 2021
tidyType: also tidy multiplicities
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I'd also like to change the string-based show instances in this file so that they wrap the strings with spaces in parens when precedence is 11 or higher, but I worry that change might be controversial. But hopefully this simpler change is not controversial, since we just preserves any existing parens in the wrapped exception.