Let definitions must not contain side-effects when reaching the kernel.

Let definitions have the same behaviour if they are ended with a Qed or a
Defined command, i.e. they are treated as if they were transparent. Indeed,
it doesn't make sense for them to be opaque as they are going to be expanded
away at the end of the section.

For an unknown reason, handling of side-effects in Let definitions considers
them as if they were opaque, i.e. the effects are inlined in the definition.

This discrepancy has bad consequences in the kernel, where one is forced to
juggle with universe constraints generated by polymorphic Let definitions.
As a first phase of cleaning, we simply enforce by typing that Let definitions
should be purified before reaching the kernel.

This has the intended side-effect to make side-effects persistent in Let
definitions, as if they were indeed truly transparent.

1 files changed, 76 insertions, 75 deletions

diff --git a/interp/declare.ml b/interp/declare.ml
index 0adad1419..8781c8719 100644
--- a/interp/declare.ml
+++ b/interp/declare.ml
@@ -31,64 +31,6 @@ type internal_flag =
   | InternalTacticRequest  (* kernel action, no message is displayed *)
   | UserIndividualRequest   (* user action, a message is displayed *)
 
-(** Declaration of section variables and local definitions *)
-
-type section_variable_entry =
-  | SectionLocalDef of Safe_typing.private_constants definition_entry
-  | SectionLocalAssum of types Univ.in_universe_context_set * polymorphic * bool (** Implicit status *)
-
-type variable_declaration = DirPath.t * section_variable_entry * logical_kind
-
-let cache_variable ((sp,_),o) =
-  match o with
-  | Inl ctx -> Global.push_context_set false ctx
-  | Inr (id,(p,d,mk)) ->
-  (* Constr raisonne sur les noms courts *)
-  if variable_exists id then
-    alreadydeclared (Id.print id ++ str " already exists");
-
-  let impl,opaq,poly,ctx = match d with (* Fails if not well-typed *)
-    | SectionLocalAssum ((ty,ctx),poly,impl) ->
-      let () = Global.push_named_assum ((id,ty,poly),ctx) in
-      let impl = if impl then Implicit else Explicit in
-	impl, true, poly, ctx
-    | SectionLocalDef (de) ->
-      let univs = Global.push_named_def (id,de) in
-      let poly = match de.const_entry_universes with
-      | Monomorphic_const_entry _ -> false
-      | Polymorphic_const_entry _ -> true
-      in
-      Explicit, de.const_entry_opaque,
-      poly, univs in
-  Nametab.push (Nametab.Until 1) (restrict_path 0 sp) (VarRef id);
-  add_section_variable id impl poly ctx;
-  Dischargedhypsmap.set_discharged_hyps sp [];
-  add_variable_data id (p,opaq,ctx,poly,mk)
-
-let discharge_variable (_,o) = match o with
-  | Inr (id,_) ->
-    if variable_polymorphic id then None
-    else Some (Inl (variable_context id))
-  | Inl _ -> Some o
-
-type variable_obj =
-    (Univ.ContextSet.t, Id.t * variable_declaration) union
-
-let inVariable : variable_obj -> obj =
-  declare_object { (default_object "VARIABLE") with
-    cache_function = cache_variable;
-    discharge_function = discharge_variable;
-    classify_function = (fun _ -> Dispose) }
-
-(* for initial declaration *)
-let declare_variable id obj =
-  let oname = add_leaf id (inVariable (Inr (id,obj))) in
-  declare_var_implicits id;
-  Notation.declare_ref_arguments_scope (VarRef id);
-  Heads.declare_head (EvalVarRef id);
-  oname
-
-
 (** Declaration of constants and parameters *)
 
 type constant_obj = {
@@ -195,6 +137,20 @@ let update_tables c =
   Heads.declare_head (EvalConstRef c);
   Notation.declare_ref_arguments_scope (ConstRef c)
 
+let register_side_effect (c, role) =
+  let o = inConstant {
+    cst_decl = None;
+    cst_hyps = [] ;
+    cst_kind = IsProof Theorem;
+    cst_locl = false;
+  } in
+  let id = Label.to_id (pi3 (Constant.repr3 c)) in
+  ignore(add_leaf id o);
+  update_tables c;
+  match role with
+  | Safe_typing.Subproof -> ()
+  | Safe_typing.Schema (ind, kind) -> !declare_scheme kind [|ind,c|]
+
 let declare_constant_common id cst =
   let o = inConstant cst in
   let _, kn as oname = add_leaf id o in
@@ -229,25 +185,11 @@ let declare_constant ?(internal = UserIndividualRequest) ?(local = false) id ?(e
       (** This globally defines the side-effects in the environment. We mark
           exported constants as being side-effect not to redeclare them at
           caching time. *)
-      let cd, export = Global.export_private_constants ~in_section cd in
-      export, ConstantEntry (PureEntry, cd)
+      let de, export = Global.export_private_constants ~in_section de in
+      export, ConstantEntry (PureEntry, DefinitionEntry de)
     | _ -> [], ConstantEntry (EffectEntry, cd)
   in
-  let iter_eff (c, role) =
-    let o = inConstant {
-      cst_decl = None;
-      cst_hyps = [] ;
-      cst_kind = IsProof Theorem;
-      cst_locl = false;
-    } in
-    let id = Label.to_id (pi3 (Constant.repr3 c)) in
-    ignore(add_leaf id o);
-    update_tables c;
-    match role with
-    | Safe_typing.Subproof -> ()
-    | Safe_typing.Schema (ind, kind) -> !declare_scheme kind [|ind,c|]
-  in
-  let () = List.iter iter_eff export in
+  let () = List.iter register_side_effect export in
   let cst = {
     cst_decl = Some decl;
     cst_hyps = [] ;
@@ -265,6 +207,65 @@ let declare_definition ?(internal=UserIndividualRequest)
     declare_constant ~internal ~local id
       (Entries.DefinitionEntry cb, Decl_kinds.IsDefinition kind)
 
+(** Declaration of section variables and local definitions *)
+
+type section_variable_entry =
+  | SectionLocalDef of Safe_typing.private_constants definition_entry
+  | SectionLocalAssum of types Univ.in_universe_context_set * polymorphic * bool (** Implicit status *)
+
+type variable_declaration = DirPath.t * section_variable_entry * logical_kind
+
+let cache_variable ((sp,_),o) =
+  match o with
+  | Inl ctx -> Global.push_context_set false ctx
+  | Inr (id,(p,d,mk)) ->
+  (* Constr raisonne sur les noms courts *)
+  if variable_exists id then
+    alreadydeclared (Id.print id ++ str " already exists");
+
+  let impl,opaq,poly,ctx = match d with (* Fails if not well-typed *)
+    | SectionLocalAssum ((ty,ctx),poly,impl) ->
+      let () = Global.push_named_assum ((id,ty,poly),ctx) in
+      let impl = if impl then Implicit else Explicit in
+        impl, true, poly, ctx
+    | SectionLocalDef (de) ->
+      let (de, eff) = Global.export_private_constants ~in_section:true de in
+      let () = List.iter register_side_effect eff in
+      let univs = Global.push_named_def (id,de) in
+      let poly = match de.const_entry_universes with
+      | Monomorphic_const_entry _ -> false
+      | Polymorphic_const_entry _ -> true
+      in
+      Explicit, de.const_entry_opaque,
+      poly, univs in
+  Nametab.push (Nametab.Until 1) (restrict_path 0 sp) (VarRef id);
+  add_section_variable id impl poly ctx;
+  Dischargedhypsmap.set_discharged_hyps sp [];
+  add_variable_data id (p,opaq,ctx,poly,mk)
+
+let discharge_variable (_,o) = match o with
+  | Inr (id,_) ->
+    if variable_polymorphic id then None
+    else Some (Inl (variable_context id))
+  | Inl _ -> Some o
+
+type variable_obj =
+    (Univ.ContextSet.t, Id.t * variable_declaration) union
+
+let inVariable : variable_obj -> obj =
+  declare_object { (default_object "VARIABLE") with
+    cache_function = cache_variable;
+    discharge_function = discharge_variable;
+    classify_function = (fun _ -> Dispose) }
+
+(* for initial declaration *)
+let declare_variable id obj =
+  let oname = add_leaf id (inVariable (Inr (id,obj))) in
+  declare_var_implicits id;
+  Notation.declare_ref_arguments_scope (VarRef id);
+  Heads.declare_head (EvalVarRef id);
+  oname
+
 (** Declaration of inductive blocks *)
 
 let declare_inductive_argument_scopes kn mie =