[econstr] Continue consolidation of EConstr API under `interp`.

This commit was motivated by true spurious conversions arising in my
`to_constr` debug branch.

The changes here need careful review as the tradeoffs are subtle and
still a lot of clean up remains to be done in `vernac/*`.

We have opted for penalize [minimally] the few users coming from true
`Constr`-land, but I am sure we can tweak code in a much better way.

In particular, it is not clear if internalization should take an
`evar_map` even in the cases where it is not triggered, see the
changes under `plugins` for a good example.

Also, the new return type of `Pretyping.understand` should undergo
careful review.

We don't touch `Impargs` as it is not clear how to proceed, however,
the current type of `compute_implicits_gen` looks very suspicious as
it is called often with free evars.

Some TODOs are:

- impargs was calling whd_all, the Econstr equivalent can be either
  + Reductionops.whd_all [which does refolding and no sharing]
  + Reductionops.clos_whd_flags with all as a flag.

1 files changed, 5 insertions, 2 deletions

diff --git a/interp/modintern.ml b/interp/modintern.ml
index e631b3ea4..128152cc2 100644
--- a/interp/modintern.ml
+++ b/interp/modintern.ml
@@ -61,13 +61,16 @@ let transl_with_decl env = function
   | CWith_Module ((_,fqid),qid) ->
       WithMod (fqid,lookup_module qid), Univ.ContextSet.empty
   | CWith_Definition ((_,fqid),c) ->
-    let c, ectx = interp_constr env (Evd.from_env env) c in
+    let sigma = Evd.from_env env in
+    let c, ectx = interp_constr env sigma c in
     if Flags.is_universe_polymorphism () then
       let ctx = UState.context ectx in
       let inst, ctx = Univ.abstract_universes ctx in
-      let c = Vars.subst_univs_level_constr (Univ.make_instance_subst inst) c in
+      let c = EConstr.Vars.subst_univs_level_constr (Univ.make_instance_subst inst) c in
+      let c = EConstr.to_constr sigma c in
       WithDef (fqid,(c, Some ctx)), Univ.ContextSet.empty
     else
+      let c = EConstr.to_constr sigma c in
       WithDef (fqid,(c, None)), UState.context_set ectx
 
 let loc_of_module l = l.CAst.loc