diff options
Diffstat (limited to 'compiler/GHC/Tc/Types/Origin.hs')
| -rw-r--r-- | compiler/GHC/Tc/Types/Origin.hs | 17 |
1 files changed, 10 insertions, 7 deletions
diff --git a/compiler/GHC/Tc/Types/Origin.hs b/compiler/GHC/Tc/Types/Origin.hs index 381cdd03ba..b453633c65 100644 --- a/compiler/GHC/Tc/Types/Origin.hs +++ b/compiler/GHC/Tc/Types/Origin.hs @@ -125,7 +125,7 @@ data UserTypeCtxt pprUserTypeCtxt :: UserTypeCtxt -> SDoc pprUserTypeCtxt (FunSigCtxt n _) = text "the type signature for" <+> quotes (ppr n) pprUserTypeCtxt (InfSigCtxt n) = text "the inferred type for" <+> quotes (ppr n) -pprUserTypeCtxt (RuleSigCtxt n) = text "a RULE for" <+> quotes (ppr n) +pprUserTypeCtxt (RuleSigCtxt n) = text "the type signature for" <+> quotes (ppr n) pprUserTypeCtxt ExprSigCtxt = text "an expression type signature" pprUserTypeCtxt KindSigCtxt = text "a kind signature" pprUserTypeCtxt (StandaloneKindSigCtxt n) = text "a standalone kind signature for" <+> quotes (ppr n) @@ -184,7 +184,10 @@ data SkolemInfo -- like SigSkol, but when we're kind-checking the *type* -- hence, we have less info - | ForAllSkol SDoc -- Bound by a user-written "forall". + | ForAllSkol -- Bound by a user-written "forall". + SDoc -- Shows the entire forall type + SDoc -- Shows just the binders, used when reporting a bad telescope + -- See Note [Checking telescopes] in GHC.Tc.Types.Constraint | DerivSkol Type -- Bound by a 'deriving' clause; -- the type is the instance we are trying to derive @@ -242,7 +245,7 @@ pprSkolInfo :: SkolemInfo -> SDoc -- Complete the sentence "is a rigid type variable bound by..." pprSkolInfo (SigSkol cx ty _) = pprSigSkolInfo cx ty pprSkolInfo (SigTypeSkol cx) = pprUserTypeCtxt cx -pprSkolInfo (ForAllSkol doc) = quotes doc +pprSkolInfo (ForAllSkol pt _) = quotes pt pprSkolInfo (IPSkol ips) = text "the implicit-parameter binding" <> plural ips <+> text "for" <+> pprWithCommas ppr ips pprSkolInfo (DerivSkol pred) = text "the deriving clause for" <+> quotes (ppr pred) @@ -306,8 +309,8 @@ is fine. We could do more, but it doesn't seem worth it. Note [SigSkol SkolemInfo] ~~~~~~~~~~~~~~~~~~~~~~~~~ -Suppose we (deeply) skolemise a type - f :: forall a. a -> forall b. b -> a +Suppose we skolemise a type + f :: forall a. Eq a => forall b. b -> a Then we'll instantiate [a :-> a', b :-> b'], and with the instantiated a' -> b' -> a. But when, in an error message, we report that "b is a rigid type @@ -321,8 +324,8 @@ in the right place. So we proceed as follows: * Then when tidying in GHC.Tc.Utils.TcMType.tidySkolemInfo, we first tidy a' to whatever it tidies to, say a''; and then we walk over the type replacing the binder a by the tidied version a'', to give - forall a''. a'' -> forall b''. b'' -> a'' - We need to do this under function arrows, to match what deeplySkolemise + forall a''. Eq a'' => forall b''. b'' -> a'' + We need to do this under (=>) arrows, to match what topSkolemise does. * Typically a'' will have a nice pretty name like "a", but the point is |