Crash on open of ascription with manifest type

[lukemaurer]

The following crashes odoc master:

module M = struct
  type t = A
end

module type S = sig
  type t = A
end

open (M : S)

The crucial bits here are that the open expression itself contains an ascription (no crash if we bind M : S to another name and open that name instead) and the ascribed module type has a manifest type in it (re-exported or otherwise). The module type can have any form so long as it evaluates to a signature with a manifest type as a member (so, in fact, the single line open (Unit : module type of Unit) suffices).

The crash happens in Cmi.read_constructor_declaration (note that we're loading from .cmt rather than .cmi; in fact, there's no crash if you start from the .cmi instead):

$ ocamlc -c module_subst_with_manifest_type3.ml -bin-annot
$ _build/install/default/bin/odoc compile module_subst_with_manifest_type3.cmt
odoc: internal error, uncaught exception:
      Not_found
      Raised at Ident.find_same in file "typing/ident.ml", line 253, characters 6-21
      Called from Odoc_loader__Cmi.read_constructor_declaration in file "src/loader/cmi.ml", line 630, characters 11-61
      Called from Stdlib__list.map in file "list.ml", line 92, characters 20-23
      Called from Odoc_loader__Cmi.read_type_kind.(fun) in file "src/loader/cmi.ml", line 649, characters 10-66
      Called from Odoc_loader__Cmi.read_type_declaration in file "src/loader/cmi.ml", line 716, characters 23-86
      Called from Odoc_loader__Cmi.read_signature_noenv.loop in file "src/loader/cmi.ml", line 1006, characters 19-59
      Called from Odoc_loader__Cmt.read_open in file "src/loader/cmt.ml", line 572, characters 21-96
      Called from Odoc_loader__Cmt.read_structure_item in file "src/loader/cmt.ml", line 520, characters 14-38
      Called from Odoc_loader__Cmt.read_structure.(fun) in file "src/loader/cmt.ml", line 592, characters 24-61
      Called from Stdlib__list.fold_left in file "list.ml", line 121, characters 24-34
      Called from Odoc_loader__Cmt.read_structure in file "src/loader/cmt.ml", line 590, characters 4-127
      Called from Odoc_loader__Cmt.read_implementation in file "src/loader/cmt.ml", line 605, characters 4-79
      Called from Odoc_loader.read_cmt in file "src/loader/odoc_loader.ml", line 170, characters 34-74
      Called from Odoc_loader.wrap_errors.(fun) in file "src/loader/odoc_loader.ml", line 193, characters 10-14
      Called from Odoc_model__Error.catch in file "src/model/error.ml", line 54, characters 21-27
      Called from Odoc_model__Error.catch_warnings.(fun) in file "src/model/error.ml", line 89, characters 18-22
      Called from Odoc_model__Error.with_ref in file "src/model/error.ml", line 67, characters 12-16
      Re-raised at Odoc_model__Error.with_ref in file "src/model/error.ml", line 72, characters 4-11
      Called from Odoc_odoc__Compile.resolve_and_substitute in file "src/odoc/compile.ml", line 111, characters 8-101
      Called from Odoc_model__Error.catch in file "src/model/error.ml", line 54, characters 21-27
      Called from Odoc_model__Error.catch_warnings.(fun) in file "src/model/error.ml", line 89, characters 18-22
      Called from Odoc_model__Error.with_ref in file "src/model/error.ml", line 67, characters 12-16
      Re-raised at Odoc_model__Error.with_ref in file "src/model/error.ml", line 72, characters 4-11
      Called from Odoc_odoc__Compile.compile.(fun) in file "src/odoc/compile.ml", line 298, characters 6-199
      Called from Dune__exe__Main.Compile.compile.(fun) in file "src/odoc/bin/main.ml", line 222, characters 4-147
      Called from Cmdliner_term.app.(fun) in file "cmdliner_term.ml", line 24, characters 19-24
      Called from Cmdliner_term.app.(fun) in file "cmdliner_term.ml", line 22, characters 12-19
      Called from Cmdliner_eval.run_parser in file "cmdliner_eval.ml", line 34, characters 37-44

[c-cube]

I have a similar issue on ocaml-trace at ecf51ce32b4a6fdc038383c1f8b0910055ee7e35 with odoc 2.4. Not sure if it's the same trigger but it looks like the same error:

$ dune build @doc 
…
File "src/fuchsia/write/.trace_fuchsia_write.objs/byte/_unknown_", line 1, characters 0-0:
odoc: internal error, uncaught exception:
      Not_found
      Raised at Ident.find_same in file "typing/ident.ml", line 266, characters 6-21
      Called from Odoc_loader__Ident_env.find_exception_identifier in file "src/loader/ident_env.cppo.ml" (inlined), line 654, characters 2-35
      Called from Odoc_loader__Cmi.read_exception in file "src/loader/cmi.ml", line 775, characters 11-47
      Called from Odoc_loader__Cmi.read_signature_noenv.loop in file "src/loader/cmi.ml", line 1028, characters 18-50
      Called from Odoc_loader__Cmt.read_open in file "src/loader/cmt.ml", line 572, characters 21-96
      Called from Odoc_loader__Cmt.read_structure_item in file "src/loader/cmt.ml", line 520, characters 14-38
      Called from Odoc_loader__Cmt.read_structure.(fun) in file "src/loader/cmt.ml", line 592, characters 24-61
      Called from Stdlib__List.fold_left in file "list.ml", line 123, characters 24-34
      Called from Odoc_loader__Cmt.read_structure in file "src/loader/cmt.ml", line 590, characters 4-127
      Called from Odoc_loader__Cmt.read_implementation in file "src/loader/cmt.ml", line 605, characters 4-79
      Called from Odoc_loader.read_cmt in file "src/loader/odoc_loader.ml", line 169, characters 34-74
      Called from Odoc_loader.wrap_errors.(fun) in file "src/loader/odoc_loader.ml", line 192, characters 10-14
      Called from Odoc_model__Error.catch in file "src/model/error.ml", line 54, characters 21-27
      Called from Odoc_model__Error.catch_warnings.(fun) in file "src/model/error.ml", line 89, characters 18-22
      Called from Odoc_model__Error.with_ref in file "src/model/error.ml", line 67, characters 12-16
      Re-raised at Odoc_model__Error.with_ref in file "src/model/error.ml", line 72, characters 4-11
      Called from Odoc_odoc__Compile.resolve_and_substitute in file "src/odoc/compile.ml", line 111, characters 8-72
      Called from Odoc_model__Error.catch in file "src/model/error.ml", line 54, characters 21-27
      Called from Odoc_model__Error.catch_warnings.(fun) in file "src/model/error.ml", line 89, characters 18-22
      Called from Odoc_model__Error.with_ref in file "src/model/error.ml", line 67, characters 12-16
      Re-raised at Odoc_model__Error.with_ref in file "src/model/error.ml", line 72, characters 4-11
      Called from Odoc_odoc__Compile.compile.(fun) in file "src/odoc/compile.ml", line 297, characters 6-180
      Called from Cmdliner_term.app.(fun) in file "cmdliner_term.ml", line 24, characters 19-24
      Called from Cmdliner_term.app.(fun) in file "cmdliner_term.ml", line 22, characters 12-19
      Called from Cmdliner_eval.run_parser in file "cmdliner_eval.ml", line 34, characters 37-44

[jonludlam]

Should be fixed by #1082