X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcInstDcls.lhs;fp=compiler%2Ftypecheck%2FTcInstDcls.lhs;h=ecdda437bc57a352d241f6e12f6ef2f394137ef4;hp=3bb27a78dec903fb9a33d68630c559902735a2cd;hb=9591547fbbdf12728884e125f8ba08b0e6e69f82;hpb=2d5205118357cac8a2dd43b33bcd93a3c00f5558

diff --git a/compiler/typecheck/TcInstDcls.lhs b/compiler/typecheck/TcInstDcls.lhs
index 3bb27a7..ecdda43 100644
--- a/compiler/typecheck/TcInstDcls.lhs
+++ b/compiler/typecheck/TcInstDcls.lhs
@@ -621,6 +621,9 @@ tcInstDecl2 (InstInfo { iSpec = ispec, iBinds = ibinds })
     addErrCtxt (instDeclCtxt2 (idType dfun_id)) $ 
     do {  -- Instantiate the instance decl with skolem constants
        ; (inst_tyvars, dfun_theta, inst_head) <- tcSkolDFunType (idType dfun_id)
+                     -- We instantiate the dfun_id with superSkolems.
+                     -- See Note [Subtle interaction of recursion and overlap]
+                     -- and Note [Binding when looking up instances]
        ; let (clas, inst_tys) = tcSplitDFunHead inst_head
              (class_tyvars, sc_theta, _, op_items) = classBigSig clas
              sc_theta' = substTheta (zipOpenTvSubst class_tyvars inst_tys) sc_theta
@@ -699,7 +702,7 @@ tcInstDecl2 (InstInfo { iSpec = ispec, iBinds = ibinds })
                  listToBag meth_binds)
        }
  where
-   skol_info = InstSkol         -- See Note [Subtle interaction of recursion and overlap]
+   skol_info = InstSkol         
    dfun_ty   = idType dfun_id
    dfun_id   = instanceDFunId ispec
    loc       = getSrcSpan dfun_id