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| author | Simon Peyton Jones <simonpj@microsoft.com> | 2019-03-13 11:15:20 +0000 |
|---|---|---|
| committer | Marge Bot <ben+marge-bot@smart-cactus.org> | 2019-03-16 08:08:25 -0400 |
| commit | 4927117cd6166a97455d788dbf7433c95441b57a (patch) | |
| tree | 07a0e4b2277d0db641254f8b4c0c2fe3f33d588f /compiler/typecheck/TcRnExports.hs | |
| parent | 57201bebaeb15c5635ac5ea153b0141b55670199 (diff) | |
| download | haskell-4927117cd6166a97455d788dbf7433c95441b57a.tar.gz | |
Improve error recovery in the typechecker
Issue #16418 showed that we were carrying on too eagerly after a bogus
type signature was identified (a bad telescope in fact), leading to a
subsequent crash.
This led me in to a maze of twisty little passages in the typechecker's
error recovery, and I ended up doing some refactoring in TcRnMonad.
Some specfifics
* TcRnMonad.try_m is now called attemptM.
* I switched the order of the result pair in tryTc,
to make it consistent with other similar functions.
* The actual exception used in the Tc monad is irrelevant so,
to avoid polluting type signatures, I made tcTryM, a simple
wrapper around tryM, and used it.
The more important changes are in
* TcSimplify.captureTopConstraints, where we should have been calling
simplifyTop rather than reportUnsolved, so that levity defaulting
takes place properly.
* TcUnify.emitResidualTvConstraint, where we need to set the correct
status for a new implication constraint. (Previously we ended up
with an Insoluble constraint wrapped in an Unsolved implication,
which meant that insolubleWC gave the wrong answer.
Diffstat (limited to 'compiler/typecheck/TcRnExports.hs')
| -rw-r--r-- | compiler/typecheck/TcRnExports.hs | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/compiler/typecheck/TcRnExports.hs b/compiler/typecheck/TcRnExports.hs index f584a7fceb..e4009e6040 100644 --- a/compiler/typecheck/TcRnExports.hs +++ b/compiler/typecheck/TcRnExports.hs @@ -140,10 +140,10 @@ accumExports :: (ExportAccum -> x -> TcRn (Maybe (ExportAccum, y))) -> TcRn [y] accumExports f = fmap (catMaybes . snd) . mapAccumLM f' emptyExportAccum where f' acc x = do - m <- try_m (f acc x) + m <- attemptM (f acc x) pure $ case m of - Right (Just (acc', y)) -> (acc', Just y) - _ -> (acc, Nothing) + Just (Just (acc', y)) -> (acc', Just y) + _ -> (acc, Nothing) type ExportOccMap = OccEnv (Name, IE GhcPs) -- Tracks what a particular exported OccName @@ -192,7 +192,7 @@ tcRnExports explicit_mod exports ; let do_it = exports_from_avail real_exports rdr_env imports this_mod ; (rn_exports, final_avails) <- if hsc_src == HsigFile - then do (msgs, mb_r) <- tryTc do_it + then do (mb_r, msgs) <- tryTc do_it case mb_r of Just r -> return r Nothing -> addMessages msgs >> failM |