flambda-backend: Refactor Persistent_env to separate imports from b…

…ound names (#2585)

With the advent of parameters, we have reasons to refer to global module names
besides those names being runtime global variables, or addressable values at
all. In addition, we're going to want to load a .cmi but then parameterise it
in different ways to get different signatures, each of which will be bound to
a separate value.

In the end, then, instead of just `pers_struct`, we'll want three different
record types, each with an associated cache:

* `import`, corresponding directly to a .cmi file, keyed by
  `Compilation_unit.Name.t`
* `pers_name`, corresponding to an `import` with parameters applied to it, keyed
  by a `Compilation_unit.Name.t` and some parameters
* `pers_struct`, corresponding to a persistent name that is actually bound in
  the environment, with the same key as `pers_name`

For this PR, I'm leaving out the second cache as nothing about it is relevant
yet, but the split is disruptive enough that even the two are worthwhile. Note
that `pers_struct` is currently still keyed by `Compilation_unit.Name.t` since
we don't yet have the datatypes for parameterised names.

Besides the internal reorganisation of `Persistent_env`, this also changes the
API between it and `Env`, offloading some of the work done by the callback,
`read_sign_of_cmi`. Significantly, `read_sign_of_cmi` is no longer called _at
all_ until something is going to be bound (i.e., become a `pers_struct`). This
keeps the `Env.t` completely free of anything it shouldn't know about.

.depend

@@ -1321,35 +1321,43 @@ typing/patterns.cmi : \
     parsing/asttypes.cmi
 typing/persistent_env.cmo : \
     utils/warnings.cmi \
+    typing/subst.cmi \
+    typing/shape.cmi \
     utils/misc.cmi \
     parsing/location.cmi \
     utils/load_path.cmi \
     utils/lazy_backtrack.cmi \
     utils/import_info.cmi \
+    typing/ident.cmi \
     utils/consistbl.cmi \
     utils/compilation_unit.cmi \
     file_formats/cmi_format.cmi \
     utils/clflags.cmi \
     typing/persistent_env.cmi
 typing/persistent_env.cmx : \
     utils/warnings.cmx \
+    typing/subst.cmx \
+    typing/shape.cmx \
     utils/misc.cmx \
     parsing/location.cmx \
     utils/load_path.cmx \
     utils/lazy_backtrack.cmx \
     utils/import_info.cmx \
+    typing/ident.cmx \
     utils/consistbl.cmx \
     utils/compilation_unit.cmx \
     file_formats/cmi_format.cmx \
     utils/clflags.cmx \
     typing/persistent_env.cmi
 typing/persistent_env.cmi : \
     typing/subst.cmi \
+    typing/shape.cmi \
     utils/misc.cmi \
     parsing/location.cmi \
     utils/load_path.cmi \
     utils/lazy_backtrack.cmi \
     utils/import_info.cmi \
+    typing/ident.cmi \
     utils/consistbl.cmi \
     utils/compilation_unit.cmi \
     file_formats/cmi_format.cmi

testsuite/tests/templates/basic/bad_param_impl.ml

@@ -9,8 +9,6 @@
  ocamlc_byte_exit_status = "2";
  compiler_output = "bad_param_impl.output";
  ocamlc.byte;
- reason = "error broken, will be fixed by #1764";
- skip;
  compiler_reference = "bad_param_impl.reference";
  check-ocamlc.byte-output;
 *)

testsuite/tests/templates/basic/test.ml

@@ -8,8 +8,6 @@
  compiler_output = "bad_ref_direct.output";
  ocamlc_byte_exit_status = "2";
  ocamlc.byte;
- reason = "correct error message not yet implemented";
- skip;
  compiler_reference = "bad_ref_direct.reference";
  check-ocamlc.byte-output;
 *)

typing/env.ml

@@ -173,7 +173,7 @@ let map_summary f = function
   | Env_value_unbound (s, u, r) -> Env_value_unbound (f s, u, r)
   | Env_module_unbound (s, u, r) -> Env_module_unbound (f s, u, r)
 
-type address =
+type address = Persistent_env.address =
   | Aunit of Compilation_unit.t
   | Alocal of Ident.t
   | Adot of address * int
@@ -953,34 +953,24 @@ let components_of_module ~alerts ~uid env ps path addr mty shape =
     }
   }
 
-let read_sign_of_cmi { Persistent_env.Persistent_signature.cmi; _ } =
-  let name =
-    match cmi.cmi_kind with
-    | Normal { cmi_impl } -> cmi_impl
-    | Parameter -> Misc.fatal_error "Unsupported import of parameter module"
-  in
-  let sign = cmi.cmi_sign in
-  let flags = cmi.cmi_flags in
-  let id = Ident.create_persistent (Compilation_unit.name_as_string name) in
+let read_sign_of_cmi sign name uid ~shape ~address:addr ~flags =
+  let id = Ident.create_persistent (Compilation_unit.Name.to_string name) in
   let path = Pident id in
   let alerts =
     List.fold_left (fun acc -> function Alerts s -> s | _ -> acc)
       Misc.Stdlib.String.Map.empty
       flags
   in
-  let sign = Subst.Lazy.signature Make_local Subst.identity sign in
   let md =
     { Subst.Lazy.md_type = Mty_signature sign;
       md_loc = Location.none;
       md_attributes = [];
-      md_uid = Uid.of_compilation_unit_id name;
+      md_uid = uid;
     }
   in
-  let mda_address = Lazy_backtrack.create_forced (Aunit name) in
+  let mda_address = Lazy_backtrack.create_forced addr in
   let mda_declaration = md in
-  let mda_shape =
-    Shape.for_persistent_unit (name |> Compilation_unit.full_path_as_string)
-  in
+  let mda_shape = shape in
   let mda_components =
     let mty = md.md_type in
     components_of_module ~alerts ~uid:md.md_uid
@@ -1016,7 +1006,7 @@ let check_pers_mod ~loc name =
   Persistent_env.check !persistent_env read_sign_of_cmi ~loc name
 
 let crc_of_unit name =
-  Persistent_env.crc_of_unit !persistent_env read_sign_of_cmi name
+  Persistent_env.crc_of_unit !persistent_env name
 
 let is_imported_opaque modname =
   Persistent_env.is_imported_opaque !persistent_env modname
@@ -2646,13 +2636,8 @@ let open_signature
 
 (* Read a signature from a file *)
 let read_signature modname filename ~add_binding =
-  let mda =
-    read_pers_mod modname filename ~add_binding
-  in
-  let md = Subst.Lazy.force_module_decl mda.mda_declaration in
-  match md.md_type with
-  | Mty_signature sg -> sg
-  | Mty_ident _ | Mty_functor _ | Mty_alias _ | Mty_strengthen _ -> assert false
+  let mty = read_pers_mod modname filename ~add_binding in
+  Subst.Lazy.force_signature mty
 
 let is_identchar_latin1 = function
   | 'A'..'Z' | 'a'..'z' | '_' | '\192'..'\214' | '\216'..'\246'