Replace mkTvSubstPrs (a `zip` b) with zipTvSubst a b

It's just a small cleanup. There should be no change in
behaviour.

Test Plan: ./validate --slow

Reviewers: austin, bgamari, simonpj

Reviewed By: simonpj

Subscribers: thomie, simonmar

Differential Revision: https://phabricator.haskell.org/D1901

compiler/basicTypes/MkId.hs

@@ -563,7 +563,7 @@ mkDataConRep dflags fam_envs wrap_name mb_bangs data_con
     mk_boxer :: [Boxer] -> DataConBoxer
     mk_boxer boxers = DCB (\ ty_args src_vars ->
                       do { let (ex_vars, term_vars) = splitAtList ex_tvs src_vars
-                               subst1 = mkTvSubstPrs (univ_tvs `zip` ty_args)
+                               subst1 = zipTvSubst univ_tvs ty_args
                                subst2 = extendTCvSubstList subst1 ex_tvs
                                                            (mkTyVarTys ex_vars)
                          ; (rep_ids, binds) <- go subst2 boxers term_vars

compiler/deSugar/DsExpr.hs

@@ -623,7 +623,7 @@ dsExpr expr@(RecordUpd { rupd_expr = record_expr, rupd_flds = fields
     mk_alt upd_fld_env con
       = do { let (univ_tvs, ex_tvs, eq_spec,
                   prov_theta, _req_theta, arg_tys, _) = conLikeFullSig con
-                 subst = mkTvSubstPrs (univ_tvs `zip` in_inst_tys)
+                 subst = zipTvSubst univ_tvs in_inst_tys
 
                 -- I'm not bothering to clone the ex_tvs
            ; eqs_vars   <- mapM newPredVarDs (substTheta subst (eqSpecPreds eq_spec))

compiler/typecheck/TcPat.hs

@@ -1011,7 +1011,7 @@ addDataConStupidTheta data_con inst_tys
         -- The origin should always report "occurrence of C"
         -- even when C occurs in a pattern
     stupid_theta = dataConStupidTheta data_con
-    tenv = mkTvSubstPrs (dataConUnivTyVars data_con `zip` inst_tys)
+    tenv = zipTvSubst (dataConUnivTyVars data_con) inst_tys
          -- NB: inst_tys can be longer than the univ tyvars
          --     because the constructor might have existentials
     inst_theta = substTheta tenv stupid_theta