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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/ghci | |
| 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/ghci')
| -rw-r--r-- | compiler/ghci/RtClosureInspect.hs | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/compiler/ghci/RtClosureInspect.hs b/compiler/ghci/RtClosureInspect.hs index 436b756af6..c64ffa9ec3 100644 --- a/compiler/ghci/RtClosureInspect.hs +++ b/compiler/ghci/RtClosureInspect.hs @@ -765,7 +765,7 @@ cvObtainTerm hsc_env max_depth force old_ty hval = runTR hsc_env $ do then parens (text "already monomorphic: " <> ppr my_ty) else Ppr.empty) Right dcname <- liftIO $ constrClosToName hsc_env clos - (_,mb_dc) <- tryTc (tcLookupDataCon dcname) + (mb_dc, _) <- tryTc (tcLookupDataCon dcname) case mb_dc of Nothing -> do -- This can happen for private constructors compiled -O0 -- where the .hi descriptor does not export them @@ -981,7 +981,7 @@ cvReconstructType hsc_env max_depth old_ty hval = runTR_maybe hsc_env $ do ConstrClosure{ptrArgs=pArgs} -> do Right dcname <- liftIO $ constrClosToName hsc_env clos traceTR (text "Constr1" <+> ppr dcname) - (_,mb_dc) <- tryTc (tcLookupDataCon dcname) + (mb_dc, _) <- tryTc (tcLookupDataCon dcname) case mb_dc of Nothing-> do forM pArgs $ \x -> do |