[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, 4 insertions, 6 deletions

diff --git a/vernac/comFixpoint.ml b/vernac/comFixpoint.ml
index 489f299a2..edfe7aa81 100644
--- a/vernac/comFixpoint.ml
+++ b/vernac/comFixpoint.ml
@@ -212,8 +212,7 @@ let interp_recursive ~program_mode ~cofix fixl notations =
   let env_rec = push_named_context rec_sign env in
 
   (* Get interpretation metadatas *)
-  let fixtypes = List.map EConstr.Unsafe.to_constr fixtypes in
-  let impls = compute_internalization_env env Recursive fixnames fixtypes fiximps in
+  let impls = compute_internalization_env env sigma Recursive fixnames fixtypes fiximps in
 
   (* Interp bodies with rollback because temp use of notations/implicit *)
   let sigma, fixdefs =
@@ -226,10 +225,9 @@ let interp_recursive ~program_mode ~cofix fixl notations =
 
   (* Instantiate evars and check all are resolved *)
   let sigma = solve_unif_constraints_with_heuristics env_rec sigma in
-  let sigma, nf = nf_evars_and_universes sigma in
-  let fixdefs = List.map (fun c -> Option.map EConstr.Unsafe.to_constr c) fixdefs in
-  let fixdefs = List.map (Option.map nf) fixdefs in
-  let fixtypes = List.map nf fixtypes in
+  let sigma, _ = nf_evars_and_universes sigma in
+  let fixdefs = List.map (fun c -> Option.map EConstr.(to_constr sigma) c) fixdefs in
+  let fixtypes = List.map EConstr.(to_constr sigma) fixtypes in
   let fixctxs = List.map (fun (_,ctx) -> ctx) fixctxs in
 
   (* Build the fix declaration block *)