libraries/proposals/monad-fail.md

@@ -199,25 +199,22 @@ Both of those tell us the "real" desugaring as just another pattern we could rec
 
 - Help! My code is broken because of a missing `MonadFail` instance! *Here are your options:*
 
-  1. Write a `MonadFail` instance (and bring it into scope)
+  1. Write a `MonadFail` instance (and bring it into scope). The [ fail](http://hackage.haskell.org/package/fail) provides a forward-compatible `MonadFail` class for GHC versions prior to GHC 8.0
 
     ```
-    #if !MIN_VERSION_base(4,11,0)
-    -- Control.Monad.Fail import will become redundant in GHC 7.16+
-    import qualified Control.Monad.Fail as Fail
-    #endif
     import Control.Monad
+    -- Control.Monad.Fail import will become redundant in GHC 8.8+
+    import qualified Control.Monad.Fail as Fail
 
     instance Monad Foo where
-     (>>=) = <...bind impl...>
-     -- NB: `return` defaults to `pure`
-    #if !MIN_VERSION_base(4,11,0)
-     -- Monad(fail) will be removed in GHC 7.16+
-     fail = Fail.fail
-    #endif
+      (>>=) = <...bind impl...>
+      -- NB: `return` defaults to `pure` since GHC 7.10
+
+      -- Monad(fail) will be removed in GHC 8.8+
+      fail = Fail.fail
 
     instance MonadFail Foo where
-     fail = <...fail implementation...>
+      fail = <...fail implementation...>
     ```
   1. Change your pattern to be irrefutable
   1. Emulate the old behaviour by desugaring the pattern match by hand:
@@ -225,7 +222,11 @@ Both of those tell us the "real" desugaring as just another pattern we could rec
     ```
     do Left e <- foobar
       stuff
-    }}} becomes {{{#!haskell
+    ```
+
+    becomes
+
+    ```
     do x <- foobar
       e <- case x of
           Left e' -> e'
@@ -277,6 +278,9 @@ The roadmap is similar to the [ AMP](https://github.com/quchen/articles/blob/mas
   - Add a language extension `-XMonadFailDesugaring` that changes desugaring to use `MonadFail(fail)` instead of `Monad(fail)` This has the effect that typechecking will infer a `MonadFail` constraint for `do` blocks with failable patterns, just as it is planned to do when the entire thing is done.
   - Add a warning when a `do` block that contains a failable pattern is desugared, but there is no `MonadFail` instance in scope: "Please add the instance or change your pattern matching." Add a flag to control whether this warning appears, but leave it off by default.
   - Add a warning when an instance implements the `fail` function (or when `fail` is imported as a method of `Monad` , as it will be removed from the `Monad` class in the future. (See also [ GHC \#10071](https://ghc.haskell.org/trac/ghc/ticket/10071)). Leave it off by default.
+- GHC 8.2 
+
+  - *(nothing happens)*
 - GHC 8.4
 
   - Turn on the warning about missing `MonadFail` instances that we added in 8.0 by default.