[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, 1 insertions, 2 deletions

diff --git a/pretyping/pretyping.ml b/pretyping/pretyping.ml
index 6700748eb..79d255b0b 100644
--- a/pretyping/pretyping.ml
+++ b/pretyping/pretyping.ml
@@ -1205,8 +1205,7 @@ let all_no_fail_flags = default_inference_flags false
 
 let ise_pretype_gen_ctx flags env sigma lvar kind c =
   let evd, c, _ = ise_pretype_gen flags env sigma lvar kind c in
-  let evd, f = Evarutil.nf_evars_and_universes evd in
-    f (EConstr.Unsafe.to_constr c), Evd.evar_universe_context evd
+  c, Evd.evar_universe_context evd
 
 (** Entry points of the high-level type synthesis algorithm *)