[Git][ghc/ghc][wip/T18626] PmCheck: Long-distance information for LocalBinds (#18626)
Sebastian Graf
gitlab at gitlab.haskell.org
Mon Sep 21 16:07:14 UTC 2020
Sebastian Graf pushed to branch wip/T18626 at Glasgow Haskell Compiler / GHC
Commits:
9d298eaa by Sebastian Graf at 2020-09-21T18:07:04+02:00
PmCheck: Long-distance information for LocalBinds (#18626)
Now `desugarLocalBind` (formerly `desugarLet`) reasons about
* The `abs_binds` of an `AbsBinds` post type-checking, or
* `FunBind`s that
* Have no pattern matches (so which aren't functions)
* Have a singleton match group with a single GRHS
* (which may have guards)
And desugars to `PmLet` LYG-style guards. Since GRHSs are no longer
denoted simply by `NonEmpty PmGRHS`, but also need to carry a `[PmGrd]`
for the `PmLet`s from `LocalBind`s, I added `PmGRHSs` to capture that.
There's a regression test in `T18626`. Fixes #18626.
- - - - -
3 changed files:
- compiler/GHC/HsToCore/PmCheck.hs
- + testsuite/tests/pmcheck/should_compile/T18626.hs
- testsuite/tests/pmcheck/should_compile/all.T
Changes:
=====================================
compiler/GHC/HsToCore/PmCheck.hs
=====================================
@@ -142,7 +142,7 @@ covCheckGRHSs hs_ctxt guards@(GRHSs _ grhss _) = do
result <- unCA (checkGRHSs matches) missing
tracePm "}: " (ppr (cr_uncov result))
formatReportWarnings cirbsGRHSs ctxt [] result
- return (ldiGRHS <$> cr_ret result)
+ return (ldiGRHSs (cr_ret result))
-- | Check a list of syntactic 'Match'es (part of case, functions, etc.), each
-- with a 'Pat' and one or more 'GRHSs':
@@ -322,7 +322,11 @@ newtype PmMatchGroup p = PmMatchGroup (NonEmpty (PmMatch p))
-- | A guard tree denoting 'Match': A payload describing the pats and a bunch of
-- GRHS.
-data PmMatch p = PmMatch { pm_pats :: !p, pm_grhss :: !(NonEmpty (PmGRHS p)) }
+data PmMatch p = PmMatch { pm_pats :: !p, pm_grhss :: !(PmGRHSs p) }
+
+-- | A guard tree denoting 'GRHSs': A bunch of local binds for long-distance
+-- information and the actual list of 'GRHS'.
+data PmGRHSs p = PmGRHSs { pgs_lcls :: !p, pgs_grhss :: !(NonEmpty (PmGRHS p))}
-- | A guard tree denoting 'GRHS': A payload describing the grds and a 'SrcInfo'
-- useful for printing out in warnings messages.
@@ -363,6 +367,10 @@ instance Outputable (PmMatch Pre) where
ppr (PmMatch { pm_pats = grds, pm_grhss = grhss }) =
pprLygGuards grds <+> ppr grhss
+instance Outputable (PmGRHSs Pre) where
+ ppr (PmGRHSs { pgs_lcls = _lcls, pgs_grhss = grhss }) =
+ ppr grhss
+
instance Outputable (PmGRHS Pre) where
ppr (PmGRHS { pg_grds = grds, pg_rhs = rhs }) =
pprLygGuards grds <+> text "->" <+> pprSrcInfo rhs
@@ -388,6 +396,10 @@ instance Outputable (PmMatch Post) where
ppr (PmMatch { pm_pats = red, pm_grhss = grhss }) =
pprRedSets red <+> ppr grhss
+instance Outputable (PmGRHSs Post) where
+ ppr (PmGRHSs { pgs_lcls = _lcls, pgs_grhss = grhss }) =
+ ppr grhss
+
instance Outputable (PmGRHS Post) where
ppr (PmGRHS { pg_grds = red, pg_rhs = rhs }) =
pprRedSets red <+> text "->" <+> pprSrcInfo rhs
@@ -699,12 +711,14 @@ desugarMatch vars (L match_loc (Match { m_pats = pats, m_grhss = grhss })) = do
-- tracePm "desugarMatch" (vcat [ppr pats, ppr pats', ppr grhss'])
return PmMatch { pm_pats = pats', pm_grhss = grhss' }
-desugarGRHSs :: SrcSpan -> SDoc -> GRHSs GhcTc (LHsExpr GhcTc) -> DsM (NonEmpty (PmGRHS Pre))
-desugarGRHSs match_loc pp_pats grhss
- = traverse (desugarLGRHS match_loc pp_pats)
- . expectJust "desugarGRHSs"
- . NE.nonEmpty
- $ grhssGRHSs grhss
+desugarGRHSs :: SrcSpan -> SDoc -> GRHSs GhcTc (LHsExpr GhcTc) -> DsM (PmGRHSs Pre)
+desugarGRHSs match_loc pp_pats grhss = do
+ lcls <- desugarLocalBinds (grhssLocalBinds grhss)
+ grhss' <- traverse (desugarLGRHS match_loc pp_pats)
+ . expectJust "desugarGRHSs"
+ . NE.nonEmpty
+ $ grhssGRHSs grhss
+ return PmGRHSs { pgs_lcls = lcls, pgs_grhss = grhss' }
-- | Desugar a guarded right-hand side to a single 'GrdTree'
desugarLGRHS :: SrcSpan -> SDoc -> LGRHS GhcTc (LHsExpr GhcTc) -> DsM (PmGRHS Pre)
@@ -724,7 +738,7 @@ desugarLGRHS match_loc pp_pats (L _loc (GRHS _ gs _)) = do
desugarGuard :: GuardStmt GhcTc -> DsM GrdVec
desugarGuard guard = case guard of
BodyStmt _ e _ _ -> desugarBoolGuard e
- LetStmt _ binds -> desugarLet (unLoc binds)
+ LetStmt _ binds -> desugarLocalBinds binds
BindStmt _ p e -> desugarBind p e
LastStmt {} -> panic "desugarGuard LastStmt"
ParStmt {} -> panic "desugarGuard ParStmt"
@@ -732,9 +746,32 @@ desugarGuard guard = case guard of
RecStmt {} -> panic "desugarGuard RecStmt"
ApplicativeStmt {} -> panic "desugarGuard ApplicativeLastStmt"
--- | Desugar let-bindings
-desugarLet :: HsLocalBinds GhcTc -> DsM GrdVec
-desugarLet _binds = return []
+-- | Desugar local (let and where) bindings
+desugarLocalBinds :: LHsLocalBinds GhcTc -> DsM GrdVec
+desugarLocalBinds (L _ (HsValBinds _ (XValBindsLR (NValBinds binds _)))) = do
+ concatMapM (concatMapM go . bagToList) (map snd binds)
+ where
+ -- We are only interested in FunBinds with single match groups without any
+ -- patterns.
+ go :: LHsBind GhcTc -> DsM [PmGrd]
+ go (L _ FunBind{fun_id = L _ x, fun_matches = mg})
+ | L _ [L _ Match{m_pats = [], m_grhss = grhss}] <- mg_alts mg
+ , GRHSs{grhssGRHSs = [L _ (GRHS _ _grds rhs)]} <- grhss = do
+ core_rhs <- dsLExpr rhs
+ return [PmLet x core_rhs]
+ go (L _ AbsBinds{abs_exports=exports, abs_binds = binds}) = do
+ -- Just assign polymorphic binders the same semantics as their monomorphic
+ -- counterpart if their types match. This is crucial for making sense
+ -- about any HsLocalBinds at all.
+ let go_export :: ABExport GhcTc -> Maybe PmGrd
+ go_export ABE{abe_poly = x, abe_mono = y}
+ | idType x `eqType` idType y = Just $ PmLet x (Var y)
+ | otherwise = Nothing
+ let exps = mapMaybe go_export exports
+ bs <- concatMapM go (bagToList binds)
+ return (exps ++ bs)
+ go _ = return []
+desugarLocalBinds _binds = return []
-- | Desugar a pattern guard
-- @pat <- e ==> let x = e; <guards for pat <- x>@
@@ -1019,8 +1056,9 @@ checkMatch :: PmMatch Pre -> CheckAction (PmMatch Post)
checkMatch (PmMatch { pm_pats = grds, pm_grhss = grhss }) =
leftToRight PmMatch (checkGrds grds) (checkGRHSs grhss)
-checkGRHSs :: NonEmpty (PmGRHS Pre) -> CheckAction (NonEmpty (PmGRHS Post))
-checkGRHSs = checkSequence checkGRHS
+checkGRHSs :: PmGRHSs Pre -> CheckAction (PmGRHSs Post)
+checkGRHSs (PmGRHSs { pgs_lcls = lcls, pgs_grhss = grhss }) =
+ leftToRight PmGRHSs (checkGrds lcls) (checkSequence checkGRHS grhss)
checkGRHS :: PmGRHS Pre -> CheckAction (PmGRHS Post)
checkGRHS (PmGRHS { pg_grds = grds, pg_rhs = rhs_info }) =
@@ -1085,7 +1123,10 @@ ldiMatchGroup (PmMatchGroup matches) = ldiMatch <$> matches
ldiMatch :: PmMatch Post -> (Nablas, NonEmpty Nablas)
ldiMatch (PmMatch { pm_pats = red, pm_grhss = grhss }) =
- (rs_cov red, ldiGRHS <$> grhss)
+ (rs_cov red, ldiGRHSs grhss)
+
+ldiGRHSs :: PmGRHSs Post -> NonEmpty Nablas
+ldiGRHSs (PmGRHSs { pgs_grhss = grhss }) = ldiGRHS <$> grhss
ldiGRHS :: PmGRHS Post -> Nablas
ldiGRHS (PmGRHS { pg_grds = red }) = rs_cov red
@@ -1161,8 +1202,8 @@ cirbsMatch PmMatch { pm_pats = red, pm_grhss = grhss } = do
$ applyWhen (not is_covered) markAllRedundant
$ cirb
-cirbsGRHSs :: NonEmpty (PmGRHS Post) -> DsM CIRB
-cirbsGRHSs grhss = Semi.sconcat <$> traverse cirbsGRHS grhss
+cirbsGRHSs :: PmGRHSs Post -> DsM CIRB
+cirbsGRHSs (PmGRHSs { pgs_grhss = grhss }) = Semi.sconcat <$> traverse cirbsGRHS grhss
cirbsGRHS :: PmGRHS Post -> DsM CIRB
cirbsGRHS PmGRHS { pg_grds = red, pg_rhs = info } = do
=====================================
testsuite/tests/pmcheck/should_compile/T18626.hs
=====================================
@@ -0,0 +1,11 @@
+{-# OPTIONS_GHC -Wincomplete-patterns -fforce-recomp #-}
+
+module Lib where
+
+x :: ()
+x | let y = True, y = ()
+
+f :: Int -> ()
+f _ | y = ()
+ where
+ y = True
=====================================
testsuite/tests/pmcheck/should_compile/all.T
=====================================
@@ -142,6 +142,8 @@ test('T18478', collect_compiler_stats('bytes allocated',10), compile,
['-fwarn-incomplete-patterns -fwarn-overlapping-patterns'])
test('T18533', normal, compile,
['-fwarn-incomplete-patterns -fwarn-overlapping-patterns'])
+test('T18626', normal, compile,
+ ['-fwarn-incomplete-patterns -fwarn-overlapping-patterns'])
test('T18572', normal, compile,
['-fwarn-incomplete-patterns -fwarn-incomplete-uni-patterns -fwarn-overlapping-patterns'])
test('T18670', normal, compile,
View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/9d298eaa613609cd11546ca57ec4bbacfac97920
--
View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/9d298eaa613609cd11546ca57ec4bbacfac97920
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