rescript-lang · JonoPrest · May 20, 2026 · May 20, 2026 · May 20, 2026 · May 20, 2026
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -47,6 +47,7 @@
 - Expand `super_errors` fixture coverage for warnings and errors. https://github.com/rescript-lang/rescript/pull/8429
 - Run `super_errors` fixtures in parallel (~2.4× faster locally). https://github.com/rescript-lang/rescript/pull/8430
 - Expand `super_errors` fixture coverage for the remaining reachable single-file error variants. https://github.com/rescript-lang/rescript/pull/8432
+- Add a multi-file fixture harness (`super_errors_multi`) for cross-module errors and warnings. https://github.com/rescript-lang/rescript/pull/8433
 
 
 # 13.0.0-alpha.4

diff --git a/scripts/format.sh b/scripts/format.sh
@@ -8,7 +8,7 @@ echo Formatting OCaml code...
 opam exec -- dune build @fmt --auto-promote
 
 echo Formatting ReScript code...
-files=$(find packages tests -type f \( -name "*.res" -o -name "*.resi" \) ! -name "syntaxErrors*" ! -name "generated_mocha_test.res" ! -path "tests/build_tests/super_errors/fixtures/break_keyword_binding.res" ! -path "tests/syntax_tests*" ! -path "tests/analysis_tests/tests*" ! -path "*/node_modules/*")
+files=$(find packages tests -type f \( -name "*.res" -o -name "*.resi" \) ! -name "syntaxErrors*" ! -name "generated_mocha_test.res" ! -path "tests/build_tests/super_errors/fixtures/break_keyword_binding.res" ! -path "tests/build_tests/super_errors_multi/fixtures/Iface_not_compiled/*" ! -path "tests/syntax_tests*" ! -path "tests/analysis_tests/tests*" ! -path "*/node_modules/*")
 ./cli/rescript.js format $files
 
 echo Formatting JS code...

diff --git a/scripts/format_check.sh b/scripts/format_check.sh
@@ -17,7 +17,7 @@ case "$(uname -s)" in
     fi
 
     echo "Checking ReScript code formatting..."
-    files=$(find packages tests -type f \( -name "*.res" -o -name "*.resi" \) ! -name "syntaxErrors*" ! -name "generated_mocha_test.res" ! -path "tests/build_tests/super_errors/fixtures/break_keyword_binding.res" ! -path "tests/syntax_tests*" ! -path "tests/analysis_tests/tests*" ! -path "*/node_modules/*")
+    files=$(find packages tests -type f \( -name "*.res" -o -name "*.resi" \) ! -name "syntaxErrors*" ! -name "generated_mocha_test.res" ! -path "tests/build_tests/super_errors/fixtures/break_keyword_binding.res" ! -path "tests/build_tests/super_errors_multi/fixtures/Iface_not_compiled/*" ! -path "tests/syntax_tests*" ! -path "tests/analysis_tests/tests*" ! -path "*/node_modules/*")
     if ./cli/rescript.js format --check $files; then
       printf "${successGreen}✅ ReScript code formatting ok.${reset}\n"
     else

diff --git a/tests/build_tests/super_errors_multi/.gitignore b/tests/build_tests/super_errors_multi/.gitignore
@@ -0,0 +1,6 @@
+fixtures/**/*.cmi
+fixtures/**/*.cmj
+fixtures/**/*.cmt
+fixtures/**/*.cmti
+fixtures/**/*.mjs
+fixtures/**/*.js
diff --git a/tests/build_tests/super_errors_multi/expected/Cross_abstract_type_construction.expected b/tests/build_tests/super_errors_multi/expected/Cross_abstract_type_construction.expected
@@ -0,0 +1,10 @@
+===== User.res =====
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/Cross_abstract_type_construction/User.res[0m:[2m1:18[0m
+
+  [1;31m1[0m [2m│[0m let bad: Abs.t = [1;31m1[0m
+  2 [2m│[0m 
+
+  This has type: [1;31mint[0m
+  But it's expected to have type: [1;33mAbs.t[0m
diff --git a/tests/build_tests/super_errors_multi/expected/Cross_async_promise_mismatch.expected b/tests/build_tests/super_errors_multi/expected/Cross_async_promise_mismatch.expected
@@ -0,0 +1,12 @@
+===== User.res =====
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/Cross_async_promise_mismatch/User.res[0m:[2m1:29-44[0m
+
+  [1;31m1[0m [2m│[0m let consume = (): string => [1;31mLib.fetch("api")[0m
+  2 [2m│[0m 
+
+  This has type: [1;31mpromise<string>[0m
+  But it's expected to have type: [1;33mstring[0m
+
+  - Did you mean to await this promise before using it?
diff --git a/tests/build_tests/super_errors_multi/expected/Cross_chain_of_aliases.expected b/tests/build_tests/super_errors_multi/expected/Cross_chain_of_aliases.expected
@@ -0,0 +1,12 @@
+===== C.res =====
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/Cross_chain_of_aliases/C.res[0m:[2m1:23-29[0m
+
+  [1;31m1[0m [2m│[0m let v: B.Reexport.t = [1;31m"wrong"[0m
+  2 [2m│[0m 
+
+  This has type: [1;31mstring[0m
+  But it's expected to have type: [1;33mB.Reexport.t[0m [2m(defined as[0m [1;33mint[0m[2m)[0m
+
+  You can convert [1;33mstring[0m to [1;33mint[0m with [1;33mInt.fromString[0m.
diff --git a/tests/build_tests/super_errors_multi/expected/Cross_dependent_clash.expected b/tests/build_tests/super_errors_multi/expected/Cross_dependent_clash.expected
@@ -0,0 +1,9 @@
+===== User.res =====
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/Cross_dependent_clash/User.res[0m:[2m1:21-34[0m
+
+  [1;31m1[0m [2m│[0m let _ = Sender.send([1;31m{to_: "alice"}[0m)
+  2 [2m│[0m 
+
+  Some required record fields are missing: body.
diff --git a/tests/build_tests/super_errors_multi/expected/Cross_deprecated_type.expected b/tests/build_tests/super_errors_multi/expected/Cross_deprecated_type.expected
@@ -0,0 +1,10 @@
+===== User.res =====
+
+  [1;33mWarning number 3[0m
+  [36m/.../fixtures/Cross_deprecated_type/User.res[0m:[2m1:8-15[0m
+
+  [1;33m1[0m [2m│[0m let v: [1;33mLegacy.t[0m = 1
+  2 [2m│[0m 
+
+  deprecated: Legacy.t
+  Use newType instead
diff --git a/tests/build_tests/super_errors_multi/expected/Cross_deprecated_value.expected b/tests/build_tests/super_errors_multi/expected/Cross_deprecated_value.expected
@@ -0,0 +1,10 @@
+===== User.res =====
+
+  [1;33mWarning number 3[0m
+  [36m/.../fixtures/Cross_deprecated_value/User.res[0m:[2m1:9-22[0m
+
+  [1;33m1[0m [2m│[0m let x = [1;33mLegacy.compute[0m(1)
+  2 [2m│[0m 
+
+  deprecated: Legacy.compute
+  Use computeNew instead
diff --git a/tests/build_tests/super_errors_multi/expected/Cross_dict_pattern.expected b/tests/build_tests/super_errors_multi/expected/Cross_dict_pattern.expected
@@ -0,0 +1,13 @@
+===== User.res =====
+
+  [1;33mWarning number 8[0m
+  [36m/.../fixtures/Cross_dict_pattern/User.res[0m:[2m2:3-4:3[0m
+
+  1 [2m│[0m let read = (cfg: Defs.config) =>
+  [1;33m2[0m [2m│[0m   [1;33mswitch cfg {[0m
+  [1;33m3[0m [2m│[0m [1;33m  | dict{"port": p} => p[0m
+  [1;33m4[0m [2m│[0m [1;33m  }[0m
+  5 [2m│[0m 
+
+  You forgot to handle a possible case here, for example: 
+  | {port: ?None}
diff --git a/tests/build_tests/super_errors_multi/expected/Cross_exception_arity_mismatch.expected b/tests/build_tests/super_errors_multi/expected/Cross_exception_arity_mismatch.expected
@@ -0,0 +1,9 @@
+===== User.res =====
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/Cross_exception_arity_mismatch/User.res[0m:[2m1:28-52[0m
+
+  [1;31m1[0m [2m│[0m let raise_it = () => throw([1;31mErrors.ParseError("oops")[0m)
+  2 [2m│[0m 
+
+  This variant constructor [1;33mErrors.ParseError[0m expects 2 arguments, but it's only being passed 1.
diff --git a/tests/build_tests/super_errors_multi/expected/Cross_external_argument_clash.expected b/tests/build_tests/super_errors_multi/expected/Cross_external_argument_clash.expected
@@ -0,0 +1,12 @@
+===== User.res =====
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/Cross_external_argument_clash/User.res[0m:[2m1:22-23[0m
+
+  [1;31m1[0m [2m│[0m let x = Ffi.parseInt([1;31m42[0m)
+  2 [2m│[0m 
+
+  This has type: [1;31mint[0m
+  But this function argument is expecting: [1;33mstring[0m
+
+  You can convert [1;33mint[0m to [1;33mstring[0m with [1;33mInt.toString[0m.
diff --git a/tests/build_tests/super_errors_multi/expected/Cross_gadt_pattern.expected b/tests/build_tests/super_errors_multi/expected/Cross_gadt_pattern.expected
@@ -0,0 +1,12 @@
+===== User.res =====
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/Cross_gadt_pattern/User.res[0m:[2m3:5-7[0m
+
+  1 [2m│[0m let bad: Gadt.t<int> => string = x =>
+  2 [2m│[0m   switch x {
+  [1;31m3[0m [2m│[0m   | [1;31mInt[0m(n) => n
+  4 [2m│[0m   | Pair(_, _) => "pair"
+  5 [2m│[0m   }
+
+  The GADT constructor Int of type Gadt.t must be qualified in this pattern.
diff --git a/tests/build_tests/super_errors_multi/expected/Cross_hidden_through_interface.expected b/tests/build_tests/super_errors_multi/expected/Cross_hidden_through_interface.expected
@@ -0,0 +1,17 @@
+===== User.res =====
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/Cross_hidden_through_interface/User.res[0m:[2m2:16[0m
+
+  1 [2m│[0m let v = Defs.make()
+  [1;31m2[0m [2m│[0m let leaked = v.[1;31mx[0m
+  3 [2m│[0m 
+
+  You're trying to access the record field [1;33mx[0m, but the thing you're trying to access it on is not a record. 
+
+The type of the thing you're trying to access it on is:
+
+Defs.t
+
+
+  Only records have fields that can be accessed with dot notation.
diff --git a/tests/build_tests/super_errors_multi/expected/Cross_inline_record_constructor.expected b/tests/build_tests/super_errors_multi/expected/Cross_inline_record_constructor.expected
@@ -0,0 +1,9 @@
+===== User.res =====
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/Cross_inline_record_constructor/User.res[0m:[2m1:9-23[0m
+
+  [1;31m1[0m [2m│[0m let v = [1;31mDefs.Pair(1, 2)[0m
+  2 [2m│[0m 
+
+  This constructor expects an inlined record argument.
diff --git a/tests/build_tests/super_errors_multi/expected/Cross_module_alias_dot_access.expected b/tests/build_tests/super_errors_multi/expected/Cross_module_alias_dot_access.expected
@@ -0,0 +1,11 @@
+===== User.res =====
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/Cross_module_alias_dot_access/User.res[0m:[2m3:21-26[0m
+
+  1 [2m│[0m module S = Lib.Settings
+  2 [2m│[0m 
+  [1;31m3[0m [2m│[0m let port = S.port + [1;31mS.host[0m
+  4 [2m│[0m 
+
+  The value host can't be found in S
diff --git a/...ild_tests/super_errors_multi/expected/Cross_module_open_shadow_label_constructor.expected b/...ild_tests/super_errors_multi/expected/Cross_module_open_shadow_label_constructor.expected
@@ -0,0 +1,24 @@
+===== User.res =====
+
+  [1;33mWarning number 45[0m
+  [36m/.../fixtures/Cross_module_open_shadow_label_constructor/User.res[0m:[2m5:1-6[0m
+
+  3 [2m│[0m   | Bar
+  4 [2m│[0m 
+  [1;33m5[0m [2m│[0m [1;33mopen A[0m
+  6 [2m│[0m 
+  7 [2m│[0m let v = Foo
+
+  this open statement shadows the constructor Foo (which is later used)
+
+
+  [1;33mWarning number 41[0m
+  [36m/.../fixtures/Cross_module_open_shadow_label_constructor/User.res[0m:[2m7:9-11[0m
+
+  5 [2m│[0m open A
+  6 [2m│[0m 
+  [1;33m7[0m [2m│[0m let v = [1;33mFoo[0m
+  8 [2m│[0m 
+
+  Foo belongs to several types: A.t t
+The first one was selected. Disambiguate if this is wrong.
diff --git a/tests/build_tests/super_errors_multi/expected/Cross_module_record_disambiguation.expected b/tests/build_tests/super_errors_multi/expected/Cross_module_record_disambiguation.expected
@@ -0,0 +1,11 @@
+===== User.res =====
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/Cross_module_record_disambiguation/User.res[0m:[2m1:19-23[0m
+
+  [1;31m1[0m [2m│[0m let r: Point.t = {[1;31mwidth[0m: 1, height: 2}
+  2 [2m│[0m 
+
+  The field [1;31mwidth[0m does not belong to type [1;33mPoint.t[0m
+
+  This record expression is expected to have type [1;33mPoint.t[0m
diff --git a/tests/build_tests/super_errors_multi/expected/Cross_module_type_only_no_impl.expected b/tests/build_tests/super_errors_multi/expected/Cross_module_type_only_no_impl.expected
@@ -0,0 +1,12 @@
+===== User.res =====
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/Cross_module_type_only_no_impl/User.res[0m:[2m1:17-23[0m
+
+  [1;31m1[0m [2m│[0m let x: string = [1;31mIface.v[0m
+  2 [2m│[0m 
+
+  This has type: [1;31mint[0m
+  But it's expected to have type: [1;33mstring[0m
+
+  You can convert [1;33mint[0m to [1;33mstring[0m with [1;33mInt.toString[0m.
diff --git a/tests/build_tests/super_errors_multi/expected/Cross_open_shadows_identifier.expected b/tests/build_tests/super_errors_multi/expected/Cross_open_shadows_identifier.expected
@@ -0,0 +1,11 @@
+===== User.res =====
+
+  [1;33mWarning number 44[0m
+  [36m/.../fixtures/Cross_open_shadows_identifier/User.res[0m:[2m2:1-6[0m
+
+  1 [2m│[0m let answer = "outer"
+  [1;33m2[0m [2m│[0m [1;33mopen A[0m
+  3 [2m│[0m let _ = answer
+  4 [2m│[0m 
+
+  this open statement shadows the value identifier answer (which is later used)
diff --git a/tests/build_tests/super_errors_multi/expected/Cross_optional_label_omitted.expected b/tests/build_tests/super_errors_multi/expected/Cross_optional_label_omitted.expected
@@ -0,0 +1,14 @@
+===== User.res =====
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/Cross_optional_label_omitted/User.res[0m:[2m1:9-17[0m
+
+  [1;31m1[0m [2m│[0m let s = [1;31mLib.greet[0m()
+  2 [2m│[0m 
+
+  This function call is incorrect.
+  The function has type:
+  (~name: string, ~greeting: string=?, unit) => string
+
+  - Missing arguments that must be provided: ~name
+  - Hint: Did you want to partially apply the function? You can do that by putting `...` just before the closing parens of the function call. Example: [1;33myourFn(~arg1=someVar, ...)[0m
diff --git a/tests/build_tests/super_errors_multi/expected/Cross_polyvariant_constraint.expected b/tests/build_tests/super_errors_multi/expected/Cross_polyvariant_constraint.expected
@@ -0,0 +1,16 @@
+===== User.res =====
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/Cross_polyvariant_constraint/User.res[0m:[2m1:19-25[0m
+
+  [1;31m1[0m [2m│[0m let v = Spec.pick([1;31m#Purple[0m)
+  2 [2m│[0m 
+
+  This has type: [1;31m[> #Purple][0m
+  But this function argument is expecting: [1;33mSpec.allowed[0m
+
+  The second polymorphic variant is [1;33mclosed[0m and doesn't include the constructor: [1;31m#Purple[0m.
+
+  Possible solutions:
+  - Either make the second variant [1;33mopen[0m so it can accept additional constructors. To do this, make sure the type starts with [1;33m[>[0m instead of [1;33m[[0m
+  - Or add the missing constructor to it.
diff --git a/tests/build_tests/super_errors_multi/expected/Cross_private_constructor_pattern.expected b/tests/build_tests/super_errors_multi/expected/Cross_private_constructor_pattern.expected
@@ -0,0 +1,30 @@
+===== Result.res =====
+
+  [1;33mWarning number 37[0m
+  [36m/.../fixtures/Cross_private_constructor_pattern/Result.res[0m:[2m1:1-3:11[0m
+
+  [1;33m1[0m [2m│[0m [1;33mtype t =[0m
+  [1;33m2[0m [2m│[0m [1;33m  | Loaded(string)[0m
+  [1;33m3[0m [2m│[0m [1;33m  | Loading[0m
+  4 [2m│[0m 
+  5 [2m│[0m let loaded = s => Loaded(s)
+
+  constructor Loading is never used to build values.
+Its type is exported as a private type.
+
+
+===== User.res =====
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/Cross_private_constructor_pattern/User.res[0m:[2m1:9-21[0m
+
+  [1;31m1[0m [2m│[0m let x = [1;31mResult.Loaded[0m("hello")
+  2 [2m│[0m 
+
+  [1;33mThe variant constructor Result.Loaded can't be found.[0m
+
+  - If it's defined in another module or file, bring it into scope by:
+    - Prefixing it with said module name: [1;33mTheModule.Result.Loaded[0m
+    - Or specifying its type: [1;33mlet theValue: TheModule.theType = Result.Loaded[0m
+  - Constructors and modules are both capitalized. Did you want the latter?
+    Then instead of [2mlet foo = Bar[0m, try [1;33mmodule Foo = Bar[0m.
diff --git a/tests/build_tests/super_errors_multi/expected/Cross_qualified_constructor_mismatch.expected b/tests/build_tests/super_errors_multi/expected/Cross_qualified_constructor_mismatch.expected
@@ -0,0 +1,10 @@
+===== User.res =====
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/Cross_qualified_constructor_mismatch/User.res[0m:[2m1:18-26[0m
+
+  [1;31m1[0m [2m│[0m let v: Shape.t = [1;31mColor.Red[0m
+  2 [2m│[0m 
+
+  The constructor Color.Red belongs to the variant type Color.t
+  but a constructor was expected belonging to the variant type Shape.t
diff --git a/tests/build_tests/super_errors_multi/expected/Cross_record_extra_field.expected b/tests/build_tests/super_errors_multi/expected/Cross_record_extra_field.expected
@@ -0,0 +1,11 @@
+===== User.res =====
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/Cross_record_extra_field/User.res[0m:[2m1:30-34[0m
+
+  [1;31m1[0m [2m│[0m let r: Defs.t = {a: 1, b: 2, [1;31mextra[0m: 3}
+  2 [2m│[0m 
+
+  The field [1;31mextra[0m does not belong to type [1;33mDefs.t[0m
+
+  This record expression is expected to have type [1;33mDefs.t[0m
diff --git a/tests/build_tests/super_errors_multi/expected/Cross_uncurried_arity.expected b/tests/build_tests/super_errors_multi/expected/Cross_uncurried_arity.expected
@@ -0,0 +1,9 @@
+===== User.res =====
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/Cross_uncurried_arity/User.res[0m:[2m1:23-29[0m
+
+  [1;31m1[0m [2m│[0m let bad: int => int = [1;31mLib.add[0m
+  2 [2m│[0m 
+
+  This function is expected to have [1;33m1[0m argument, but has [1;31m3[0m
diff --git a/tests/build_tests/super_errors_multi/expected/Cross_unused_open.expected b/tests/build_tests/super_errors_multi/expected/Cross_unused_open.expected
@@ -0,0 +1,10 @@
+===== User.res =====
+
+  [1;33mWarning number 33[0m
+  [36m/.../fixtures/Cross_unused_open/User.res[0m:[2m1:1-12[0m
+
+  [1;33m1[0m [2m│[0m [1;33mopen Helpers[0m
+  2 [2m│[0m 
+  3 [2m│[0m let v = 42
+
+  unused open Helpers.
diff --git a/tests/build_tests/super_errors_multi/expected/Cross_variant_spread.expected b/tests/build_tests/super_errors_multi/expected/Cross_variant_spread.expected
@@ -0,0 +1,13 @@
+===== Ext.res =====
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/Cross_variant_spread/Ext.res[0m:[2m3:8-13[0m
+
+  1 [2m│[0m type t =
+  2 [2m│[0m   | A
+  [1;31m3[0m [2m│[0m   | ...[1;31mBase.t[0m
+  4 [2m│[0m   | C
+  5 [2m│[0m 
+
+  Variant Base.t has a constructor named A, but a constructor named A already exists in the variant it's spread into.
+  You cannot spread variants with overlapping constructors.