bsc crashes with `Fatal error: exception Not_found` on `Some(x)` when the type of `x` comes from a transitive dependency

Start in compiler/ml/typeopt.ml at type_cannot_contain_undefined and inspect the Env.find_type lookup, then compare the related code from ReScript 11.1.4 and the call path through compiler/ml/env.ml. Reproduce with the provided npm workspace using npm install and npx rescript build. Done means the transitive-dependency example compiles without Fatal error: exception Not_found and preserves the existing successful cases.

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• Concise, focused, friendly issue title & description.
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bsc exits with a bare Fatal error: exception Not_found (exit code 2) when it compiles Some(x) and the type of x is declared in a package that is only a transitive dependency.
The message names no file, so it is hard to find the module that fails.

Snippet

Three packages in npm workspaces: app (the root) depends on facade, and facade depends on lib-a.

package.json:

{
  "name": "app",
  "private": true,
  "workspaces": ["packages/*"],
  "dependencies": {"rescript": "12.3.1"}
}

rescript.json:

{
  "name": "app",
  "sources": [{"dir": "src"}],
  "dependencies": ["facade"]
}

src/App.res:

let x = Some(Facade.v)

packages/facade/package.json:

{"name": "facade", "version": "1.0.0", "dependencies": {"lib-a": "1.0.0"}}

packages/facade/rescript.json:

{"name": "facade", "sources": [{"dir": "src"}], "dependencies": ["lib-a"]}

packages/facade/src/Facade.res:

let v = A.v

packages/lib-a/package.json:

{"name": "lib-a", "version": "1.0.0"}

packages/lib-a/rescript.json:

{"name": "lib-a", "sources": [{"dir": "src"}]}

packages/lib-a/src/A.res:

type t = X

let v = X

npm install
npx rescript build

Actual

Cleaned 0/0
Parsed 3 source files
Compiled 3 modules
Fatal error: exception Not_found

Incremental build failed. Error:   Failed to Compile. See Errors Above

The same with the bsc command line from npx rescript compiler-args src/App.res (paths made relative) and a backtrace:

cd lib/bs
OCAMLRUNPARAM=b ../../node_modules/@rescript/linux-x64/bin/bsc.exe -I ../ocaml -runtime-path ../../node_modules/@rescript/runtime -I ../../packages/facade/lib/ocaml -bs-package-name app -bs-package-output commonjs:src:.js src/App.ast

Fatal error: exception Not_found
Raised at Env.find_pers_struct in file "compiler/ml/env.ml", line 699, characters 12-27
Called from Env.find_pers_struct in file "compiler/ml/env.ml" (inlined), line 740, characters 28-54
Called from Env.find_module_descr in file "compiler/ml/env.ml", line 787, characters 8-42
Called from Env.find in file "compiler/ml/env.ml", line 804, characters 25-50
Called from Env.find_type in file "compiler/ml/env.ml" (inlined), line 862, characters 26-48
Called from Typeopt.type_cannot_contain_undefined in file "compiler/ml/typeopt.ml", line 51, characters 17-36
Called from Translcore.transl_exp0 in file "compiler/ml/translcore.ml", lines 829-830, characters 19-32
Called from Translcore.transl_let.transl in file "compiler/ml/translcore.ml", line 1081, characters 18-33
Called from Translmod.transl_structure in file "compiler/ml/translmod.ml", line 371, characters 7-56
Called from Translmod.transl_struct in file "compiler/ml/translmod.ml" (inlined), line 288, characters 2-73
Called from Translmod.transl_implementation in file "compiler/ml/translmod.ml", line 463, characters 16-77
Called from Js_implementation.after_parsing_impl in file "compiler/core/js_implementation.ml", line 147, characters 11-72
Called from Dune__exe__Rescript_compiler_main in file "compiler/bsc/rescript_compiler_main.ml", line 447, characters 6-75
Re-raised at Location.report_exception_rec in file "compiler/ml/location.ml", line 282, characters 14-25
Re-raised at Location.report_exception_rec in file "compiler/ml/location.ml", line 282, characters 14-25
Re-raised at Location.report_exception_rec in file "compiler/ml/location.ml", line 282, characters 14-25
Re-raised at Location.report_exception_rec in file "compiler/ml/location.ml", line 282, characters 14-25
Re-raised at Location.report_exception_rec in file "compiler/ml/location.ml", line 282, characters 14-25
Re-raised at Location.report_exception_rec in file "compiler/ml/location.ml", line 282, characters 14-25
Called from Location.report_exception in file "compiler/ml/location.ml" (inlined), line 288, characters 31-61
Called from Dune__exe__Rescript_compiler_main in file "compiler/bsc/rescript_compiler_main.ml", line 452, characters 4-35

With -I ../../packages/lib-a/lib/ocaml added, the same command exits with 0 and emits let x = Facade.v;.

It crashes the same way when A.t is a record, an abstract type, an @unboxed variant, or type t = int.
It also crashes when Facade re-exports a function of A with an optional labeled argument, and App.res passes Facade.v to it: Facade.f(~a=Facade.v) for let f = (~a: option<t>=?) => a.
It compiles when App.res uses Facade.v without Some: let x = Facade.v or let x = [Facade.v].

Expected

App.res compiles, as it did with ReScript 11.1.4 (see below).

Possible cause: in type_cannot_contain_undefined (compiler/ml/typeopt.ml), Env.find_type p env runs before match decl.type_kind with, so the | exception _ -> false case does not catch its Not_found.
In 11.1.4, the lookup was inside the match expression; it moved out in #7458.

Worked in ReScript 11

The same files with ReScript 11.1.4, and bs-dependencies instead of dependencies in both rescript.json files, build without errors.
lib/js/src/App.js:

// Generated by ReScript, PLEASE EDIT WITH CARE
'use strict';

var Facade = require("facade/lib/js/src/Facade.js");
var Caml_option = require("rescript/lib/js/caml_option.js");

var x = Caml_option.some(Facade.v);

exports.x = x;
/* No side effect */

Environment

• ReScript 12.3.1, 13.0.0-alpha.6, and master 58c6c89 (from pkg.pr.new, reports 13.0.0-alpha.7): the same crash on all three.
• Node.js 24.9.0
• Linux x86_64

Context

We hit it in a test file: a package with test helpers re-exports a test library with include (Lib: module type of Lib), and the test passed a value of an @unboxed variant type from that library to an optional labeled argument.
The tested package lists only the helper package in its dependencies.

Workaround

Add the package that declares the type (lib-a) to the dependencies of the package that fails to compile (app).