diff options
Diffstat (limited to 'compiler/GHC/Tc/Solver/Flatten.hs')
| -rw-r--r-- | compiler/GHC/Tc/Solver/Flatten.hs | 16 |
1 files changed, 15 insertions, 1 deletions
diff --git a/compiler/GHC/Tc/Solver/Flatten.hs b/compiler/GHC/Tc/Solver/Flatten.hs index 551e1de395..4dff585840 100644 --- a/compiler/GHC/Tc/Solver/Flatten.hs +++ b/compiler/GHC/Tc/Solver/Flatten.hs @@ -5,7 +5,7 @@ module GHC.Tc.Solver.Flatten( FlattenMode(..), flatten, flattenKind, flattenArgsNom, - rewriteTyVar, + rewriteTyVar, flattenType, unflattenWanteds ) where @@ -825,6 +825,20 @@ flattenArgsNom ev tc tys ; traceTcS "flatten }" (vcat (map ppr tys')) ; return (tys', cos, kind_co) } +-- | Flatten a type w.r.t. nominal equality. This is useful to rewrite +-- a type w.r.t. any givens. It does not do type-family reduction. This +-- will never emit new constraints. Call this when the inert set contains +-- only givens. +flattenType :: CtLoc -> TcType -> TcS TcType +flattenType loc ty + -- More info about FM_SubstOnly in Note [Holes] in GHC.Tc.Types.Constraint + = do { (xi, _) <- runFlatten FM_SubstOnly loc Given NomEq $ + flatten_one ty + -- use Given flavor so that it is rewritten + -- only w.r.t. Givens, never Wanteds/Deriveds + -- (Shouldn't matter, if only Givens are present + -- anyway) + ; return xi } {- ********************************************************************* * * |