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ocamlbuild foo.inferred.ml does yield a WRONG signature and ocamlc complains... #7295

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vicuna opened this Issue Jul 20, 2016 · 3 comments

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vicuna commented Jul 20, 2016

Original bug ID: 7295
Reporter: tormen
Assigned to: @gasche
Status: closed (set by @xavierleroy on 2017-09-24T15:33:13Z)
Resolution: fixed
Priority: normal
Severity: minor
Version: 4.02.3
Fixed in version: later
Category: -for ocamlbuild use https://github.com/ocaml/ocamlbuild/issues

Bug description

NOT SURE IF THIS IS AN OCAMLBUILD or ocamlc problem... as I am quite new to the ocaml ecosystem, I let you figure that out if it's okey... (but I will hungrily consume any explanation about what category this bug should or should not be assigned to :)).

inferred.mli tells me
val not_found : (unit -> 'a) -> bool and
when I compile it complains about
val not_found : (unit -> unit) -> bool
not matching
val not_found : (unit -> 'a) -> bool

Steps to reproduce

1.) foo.ml:
let not_found f = try f (); false with Not_found -> true

2.) ocamlbuild -use-ocamlfind -pkg core -tag "ppx(ppx-jane -as-ppx)" -tag thread -tag debug -tag bin_annot -tag short_paths -tag safe_string -cflags "-w +27@0..26-4@28..99-33-40-41-42-43-34-44" -cflags -strict-sequence -cflags -safe-string -verbose 0 -Is -use-ocamlfind -pkgs pgocaml,pgocaml.syntax,deriving,deriving-yojson.syntax,deriving-yojson,calendar -syntax camlp4o -tag thread foo.inferred.mli

3.) cat _build/foo.inferred.mli:
val not_found : (unit -> 'a) -> bool

4.) cp _build/foo.inferred.mli foo.mli

5.) ocamlbuild -use-ocamlfind -pkg core -tag "ppx(ppx-jane -as-ppx)" -tag thread -tag debug -tag bin_annot -tag short_paths -tag safe_string -cflags "-w +27@0..26-4@28..99-33-40-41-42-43-34-44" -cflags -strict-sequence -cflags -safe-string -verbose 0 -Is -use-ocamlfind -pkgs pgocaml,pgocaml.syntax,deriving,deriving-yojson.syntax,deriving-yojson,calendar -syntax camlp4o -tag thread foo.native

Should yield:
File "foo.ml", line 1:
Error: The implementation foo.ml does not match the interface foo.cmi:
Values do not match:
val not_found : (unit -> unit) -> bool
is not included in
val not_found : (unit -> 'a) -> bool
File "foo.ml", line 2, characters 4-13: Actual declaration
Command exited with code 2.

Additional information

So IMHO (also myself looking at the code) the _build/foo.inferred.mli should have contained:
val not_found : (unit -> unit) -> bool

(because "f (); false" means f () needs to evaluate to unit (because of the following ";" and it certainly gets a unit input, so (unit -> unit) is correct.

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vicuna commented Jul 20, 2016

Comment author: @yallop

In summary: ocamlbuild doesn't pass -strict-sequence through to 'ocamlc -i', so the inferred type used to generate the interface is more general than the type inferred when compiling the implementation.

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vicuna commented Jul 20, 2016

Comment author: tormen

Similar problem happens, when you change "f ()" to (Lazy.force f) in the above foo.ml

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vicuna commented Jul 20, 2016

Comment author: @gasche

This is indeed an ocamlbuild issue and I fixed it in

ocaml/ocamlbuild@3d8e638

It will be available in the next release of ocamlbuild.

@vicuna vicuna closed this Sep 24, 2017

@vicuna vicuna added the ocamlbuild label Mar 14, 2019

@vicuna vicuna added the bug label Mar 20, 2019

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