diff options
Diffstat (limited to 'compiler/typecheck/Inst.hs')
| -rw-r--r-- | compiler/typecheck/Inst.hs | 16 |
1 files changed, 9 insertions, 7 deletions
diff --git a/compiler/typecheck/Inst.hs b/compiler/typecheck/Inst.hs index e5b802063b..0a50de48b0 100644 --- a/compiler/typecheck/Inst.hs +++ b/compiler/typecheck/Inst.hs @@ -638,13 +638,15 @@ newClsInst overlap_mode dfun_name tvs theta clas tys = do { (subst, tvs') <- freshenTyVarBndrs tvs -- Be sure to freshen those type variables, -- so they are sure not to appear in any lookup - ; let tys' = substTys subst tys - theta' = substTheta subst theta - dfun = mkDictFunId dfun_name tvs' theta' clas tys' - -- Substituting in the DFun type just makes sure that - -- we are using TyVars rather than TcTyVars - -- Not sure if this is really the right place to do so, - -- but it'll do fine + ; let tys' = substTys subst tys + + dfun = mkDictFunId dfun_name tvs theta clas tys + -- The dfun uses the original 'tvs' because + -- (a) they don't need to be fresh + -- (b) they may be mentioned in the ib_binds field of + -- an InstInfo, and in TcEnv.pprInstInfoDetails it's + -- helpful to use the same names + ; oflag <- getOverlapFlag overlap_mode ; let inst = mkLocalInstance dfun oflag tvs' clas tys' ; warnIf (Reason Opt_WarnOrphans) |