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Within LTS Haskell 24.52 (ghc-9.10.3)

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  1. NestedAtomically :: NestedAtomically

    ghc-internal GHC.Internal.Control.Exception.Base

    No documentation available.

  2. finally :: IO a -> IO b -> IO a

    ghc-internal GHC.Internal.Control.Exception.Base

    A specialised variant of bracket with just a computation to run afterward.

  3. nestedAtomically :: SomeException

    ghc-internal GHC.Internal.Control.Exception.Base

    No documentation available.

  4. getAll :: All -> Bool

    ghc-internal GHC.Internal.Data.Monoid

    No documentation available.

  5. getAll :: All -> Bool

    ghc-internal GHC.Internal.Data.Semigroup.Internal

    No documentation available.

  6. type IOCallback = FdKey -> Event -> IO ()

    ghc-internal GHC.Internal.Event

    Callback invoked on I/O events.

  7. type TimeoutCallback = IO ()

    ghc-internal GHC.Internal.Event

    Warning: since the TimeoutCallback is called from the I/O manager, it must not throw an exception or block for a long period of time. In particular, be wary of throwTo and killThread: if the target thread is making a foreign call, these functions will block until the call completes.

  8. type TimeoutCallback = IO ()

    ghc-internal GHC.Internal.Event.TimeOut

    Warning: since the TimeoutCallback is called from the I/O manager, it must not throw an exception or block for a long period of time. In particular, be wary of throwTo and killThread: if the target thread is making a foreign call, these functions will block until the call completes.

  9. data CallStack

    ghc-internal GHC.Internal.Exception

    CallStacks are a lightweight method of obtaining a partial call-stack at any point in the program. A function can request its call-site with the HasCallStack constraint. For example, we can define 

    putStrLnWithCallStack :: HasCallStack => String -> IO ()
    as a variant of putStrLn that will get its call-site and print it, along with the string given as argument. We can access the call-stack inside putStrLnWithCallStack with callStack. 
    >>> :{
putStrLnWithCallStack :: HasCallStack => String -> IO ()
putStrLnWithCallStack msg = do
putStrLn msg
putStrLn (prettyCallStack callStack)
:}
    Thus, if we call putStrLnWithCallStack we will get a formatted call-stack alongside our string. 
    >>> putStrLnWithCallStack "hello"
hello
CallStack (from HasCallStack):
putStrLnWithCallStack, called at <interactive>:... in interactive:Ghci...
    GHC solves HasCallStack constraints in three steps:
    1. If there is a CallStack in scope -- i.e. the enclosing function has a HasCallStack constraint -- GHC will append the new call-site to the existing CallStack.
    2. If there is no CallStack in scope -- e.g. in the GHCi session above -- and the enclosing definition does not have an explicit type signature, GHC will infer a HasCallStack constraint for the enclosing definition (subject to the monomorphism restriction).
    3. If there is no CallStack in scope and the enclosing definition has an explicit type signature, GHC will solve the HasCallStack constraint for the singleton CallStack containing just the current call-site.
    CallStacks do not interact with the RTS and do not require compilation with -prof. On the other hand, as they are built up explicitly via the HasCallStack constraints, they will generally not contain as much information as the simulated call-stacks maintained by the RTS. A CallStack is a [(String, SrcLoc)]. The String is the name of function that was called, the SrcLoc is the call-site. The list is ordered with the most recently called function at the head. NOTE: The intrepid user may notice that HasCallStack is just an alias for an implicit parameter ?callStack :: CallStack. This is an implementation detail and should not be considered part of the CallStack API, we may decide to change the implementation in the future.

  10. data ErrorCall

    ghc-internal GHC.Internal.Exception

    This is thrown when the user calls error. The first String is the argument given to error, second String is the location.

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