From 5aafa890b0d1a47b982a144794db046a52bd8dea Mon Sep 17 00:00:00 2001
From: Christoph Knittel <ck@cca.io>
Date: Wed, 19 Aug 2026 11:17:25 +0200
Subject: [PATCH 01/10] Fix rewatch warning replay after early compile errors
 (#8408)

Backport the fix by tracking modules that actually recompiled, so stored warnings are replayed for dependents skipped after an earlier error.

(cherry picked from commit 56d4ed5fe678bef15e9828fe60e2e91643e589ed)

Signed-off-by: Christoph Knittel <ck@cca.io>
---
 CHANGELOG.md                 |  6 ++++++
 rewatch/src/build/compile.rs | 10 ++++++----
 rewatch/tests/watch.sh       | 36 +++++++++++++++++++++++++++++++++++-
 3 files changed, 47 insertions(+), 5 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 5c0aa152dca..22949a89a9c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,6 +10,12 @@
 > - :nail_care: [Polish]
 > - :house: [Internal]
 
+# 12.3.1 (Unreleased)
+
+#### :bug: Bug fix
+
+- Fix rewatch warning replay after early compile errors. https://github.com/rescript-lang/rescript/pull/8408
+
 # 12.3.0
 
 No changes compared to 12.3.0-beta.1.
diff --git a/rewatch/src/build/compile.rs b/rewatch/src/build/compile.rs
index 4c735df6218..827bc322e59 100644
--- a/rewatch/src/build/compile.rs
+++ b/rewatch/src/build/compile.rs
@@ -113,6 +113,7 @@ pub fn compile(
     let mut compile_errors = "".to_string();
     let mut compile_warnings = "".to_string();
     let mut num_compiled_modules = 0;
+    let mut recompiled_modules = AHashSet::<String>::new();
     let mut sorted_modules = build_state.module_names.iter().collect::<Vec<&String>>();
     sorted_modules.sort();
 
@@ -271,6 +272,7 @@ pub fn compile(
 
             if *is_compiled {
                 num_compiled_modules += 1;
+                recompiled_modules.insert(module_name.to_string());
             }
 
             files_current_loop_count += 1;
@@ -443,11 +445,11 @@ pub fn compile(
         };
     }
 
-    // Collect warnings from modules that were not recompiled in this build
-    // but still have stored warnings from a previous compilation.
-    // This ensures warnings are not lost during incremental builds in watch mode.
+    // Collect warnings from modules that were not recompiled in this build but still have stored
+    // warnings from a previous compilation. This includes modules in the compile universe that
+    // were never reached because an earlier module failed.
     for (module_name, module) in build_state.modules.iter() {
-        if compile_universe.contains(module_name) {
+        if recompiled_modules.contains(module_name) {
             continue;
         }
         if let SourceType::SourceFile(ref source_file) = module.source_type {
diff --git a/rewatch/tests/watch.sh b/rewatch/tests/watch.sh
index bcd0158956e..f5898a4e47e 100755
--- a/rewatch/tests/watch.sh
+++ b/rewatch/tests/watch.sh
@@ -39,6 +39,40 @@ else
   exit 1
 fi
 
+bold "Test: Stored warnings are replayed after an early compile error"
+warning_count=$(grep -c "unusedValue" rewatch.log || true)
+echo 'B.world()' >> ./packages/watch-warnings/src/ModuleA.res
+timeout=20
+while [ "$(grep -c "unusedValue" rewatch.log || true)" -le "$warning_count" ] && [ "$timeout" -gt 0 ]; do
+  sleep 1
+  timeout=$((timeout - 1))
+done
+if [ "$timeout" -eq 0 ]; then
+  error "Expected warning was not emitted before the error test"
+  git checkout -- ./packages/watch-warnings/src/ModuleA.res
+  exit_watcher
+  exit 1
+fi
+
+error_log_start=$(($(wc -l < rewatch.log) + 1))
+echo 'let broken: int = "broken"' >> ./packages/watch-warnings/src/B.res
+timeout=20
+while ! tail -n +"$error_log_start" rewatch.log | grep -q 'let broken' && [ "$timeout" -gt 0 ]; do
+  sleep 1
+  timeout=$((timeout - 1))
+done
+warning_replay_output=$(tail -n +"$error_log_start" rewatch.log)
+if [[ "$warning_replay_output" == *"unusedValue"* ]]; then
+  success "Stored warning was replayed"
+else
+  error "Stored warning was not replayed"
+  printf "%s\n" "$warning_replay_output" >&2
+  git checkout -- ./packages/watch-warnings/src/ModuleA.res ./packages/watch-warnings/src/B.res
+  exit_watcher
+  exit 1
+fi
+git checkout -- ./packages/watch-warnings/src/ModuleA.res ./packages/watch-warnings/src/B.res
+
 sleep 1
 
 replace '/Js.log("added-by-test")/d' ./packages/main/src/Main.res;
@@ -54,4 +88,4 @@ else
   exit 1
 fi
 
-exit_watcher
\ No newline at end of file
+exit_watcher

From 96e18fb589667444b8a74a4d66b051e4bbe3c1ec Mon Sep 17 00:00:00 2001
From: Florian Hammerschmidt <florianh89@gmail.com>
Date: Tue, 26 May 2026 15:17:01 +0200
Subject: [PATCH 02/10] Fix formatting of trailing comments before equals
 (#8444)

---
 CHANGELOG.md                                  |  1 +
 compiler/syntax/src/res_printer.ml            | 26 ++++++++++++-------
 .../comments/expected/valueBindings.res.txt   |  8 ++++++
 .../data/printer/comments/valueBindings.res   |  8 ++++++
 4 files changed, 33 insertions(+), 10 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 22949a89a9c..40c7ad606d4 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -15,6 +15,7 @@
 #### :bug: Bug fix
 
 - Fix rewatch warning replay after early compile errors. https://github.com/rescript-lang/rescript/pull/8408
+- Fix formatting of trailing comments before `=` in let bindings. https://github.com/rescript-lang/rescript/pull/8444
 
 # 12.3.0
 
diff --git a/compiler/syntax/src/res_printer.ml b/compiler/syntax/src/res_printer.ml
index 2010d23f6dd..40c2b33fcf7 100644
--- a/compiler/syntax/src/res_printer.ml
+++ b/compiler/syntax/src/res_printer.ml
@@ -70,6 +70,11 @@ let has_trailing_single_line_comment tbl loc =
   | Some (comment :: _) -> Comment.is_single_line_comment comment
   | _ -> false
 
+let has_any_trailing_line_comment tbl loc =
+  match Hashtbl.find_opt tbl.CommentTable.trailing loc with
+  | Some comments -> List.exists Comment.is_single_line_comment comments
+  | None -> false
+
 let has_comment_below tbl loc =
   match Hashtbl.find tbl.CommentTable.trailing loc with
   | comment :: _ ->
@@ -2230,7 +2235,15 @@ and print_value_binding ~state ~rec_flag (vb : Parsetree.value_binding) cmt_tbl
       | Braced braces -> print_braces doc expr braces
       | Nothing -> doc
     in
+    let pattern_has_trailing_line_comment =
+      has_any_trailing_line_comment cmt_tbl vb.pvb_pat.ppat_loc
+    in
     let pattern_doc = print_pattern ~state vb.pvb_pat cmt_tbl in
+    let equal_doc =
+      if pattern_has_trailing_line_comment then
+        Doc.indent (Doc.concat [Doc.hard_line; Doc.equal])
+      else Doc.text " ="
+    in
     (*
      * we want to optimize the layout of one pipe:
      *   let tbl = data->Js.Array2.reduce((map, curr) => {
@@ -2248,21 +2261,14 @@ and print_value_binding ~state ~rec_flag (vb : Parsetree.value_binding) cmt_tbl
         [
           Doc.group
             (Doc.concat
-               [
-                 attrs;
-                 header;
-                 pattern_doc;
-                 Doc.text " =";
-                 Doc.space;
-                 printed_expr;
-               ]);
+               [attrs; header; pattern_doc; equal_doc; Doc.space; printed_expr]);
           Doc.group
             (Doc.concat
                [
                  attrs;
                  header;
                  pattern_doc;
-                 Doc.text " =";
+                 equal_doc;
                  Doc.indent (Doc.concat [Doc.line; printed_expr]);
                ]);
         ]
@@ -2294,7 +2300,7 @@ and print_value_binding ~state ~rec_flag (vb : Parsetree.value_binding) cmt_tbl
              attrs;
              header;
              pattern_doc;
-             Doc.text " =";
+             equal_doc;
              (if should_indent then
                 Doc.indent (Doc.concat [Doc.line; printed_expr])
               else Doc.concat [Doc.space; printed_expr]);
diff --git a/tests/syntax_tests/data/printer/comments/expected/valueBindings.res.txt b/tests/syntax_tests/data/printer/comments/expected/valueBindings.res.txt
index c87a9530b1e..e5cac613d77 100644
--- a/tests/syntax_tests/data/printer/comments/expected/valueBindings.res.txt
+++ b/tests/syntax_tests/data/printer/comments/expected/valueBindings.res.txt
@@ -10,6 +10,14 @@ let walkList: 'node. unit = comments => {
   let x /* comment */ = 0
 }
 
+let x // comment before equals
+  = 1
+
+let multilineString // comment before equals
+  = "
+multiline
+"
+
 let walkList: 'node. (
   ~prevLoc: Location.t=?,
   ~getLoc: 'node => Location.t,
diff --git a/tests/syntax_tests/data/printer/comments/valueBindings.res b/tests/syntax_tests/data/printer/comments/valueBindings.res
index c47f0276e6b..b575aee5f4b 100644
--- a/tests/syntax_tests/data/printer/comments/valueBindings.res
+++ b/tests/syntax_tests/data/printer/comments/valueBindings.res
@@ -10,6 +10,14 @@ let walkList: 'node. unit = comments => {
   let x /* comment */ = 0
 }
 
+let x // comment before equals
+= 1
+
+let multilineString // comment before equals
+= "
+multiline
+"
+
 let walkList: 'node. (
   ~prevLoc: Location.t=?,
   ~getLoc: 'node => Location.t,

From 5560f61de28ec9cd1f4075d82be800a87ebba549 Mon Sep 17 00:00:00 2001
From: Benjamin Thomas <benjamin.guy.thomas@gmail.com>
Date: Tue, 2 Jun 2026 00:35:42 +0200
Subject: [PATCH 03/10] analysis: fix namespaced reference lookup (#8455)

* analysis: fix namespaced reference lookup

* analysis: demonstrate incremental CMT lookup
---
 CHANGELOG.md                                  |  1 +
 analysis/src/Cmt.ml                           | 60 ++++++++++++-------
 analysis/src/References.ml                    | 31 +++++++---
 tests/analysis_tests/Makefile                 |  2 +
 .../tests-namespaced-references/.gitignore    |  2 +
 .../tests-namespaced-references/Makefile      | 20 +++++++
 .../tests-namespaced-references/package.json  | 11 ++++
 .../tests-namespaced-references/rescript.json | 17 ++++++
 .../src/MyModule1.res                         |  6 ++
 .../src/MyModule2.res                         |  2 +
 .../src/expected/MyModule1.res.txt            |  9 +++
 .../src/expected/MyModule2.res.txt            |  5 ++
 .../tests-namespaced-references/test.sh       | 30 ++++++++++
 .../ounit_analysis_references_tests.ml        | 25 ++++++++
 tests/ounit_tests/ounit_tests_main.ml         |  1 +
 yarn.lock                                     |  8 +++
 16 files changed, 203 insertions(+), 27 deletions(-)
 create mode 100644 tests/analysis_tests/tests-namespaced-references/.gitignore
 create mode 100644 tests/analysis_tests/tests-namespaced-references/Makefile
 create mode 100644 tests/analysis_tests/tests-namespaced-references/package.json
 create mode 100644 tests/analysis_tests/tests-namespaced-references/rescript.json
 create mode 100644 tests/analysis_tests/tests-namespaced-references/src/MyModule1.res
 create mode 100644 tests/analysis_tests/tests-namespaced-references/src/MyModule2.res
 create mode 100644 tests/analysis_tests/tests-namespaced-references/src/expected/MyModule1.res.txt
 create mode 100644 tests/analysis_tests/tests-namespaced-references/src/expected/MyModule2.res.txt
 create mode 100755 tests/analysis_tests/tests-namespaced-references/test.sh
 create mode 100644 tests/ounit_tests/ounit_analysis_references_tests.ml

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 40c7ad606d4..d0e49fcf8d2 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -16,6 +16,7 @@
 
 - Fix rewatch warning replay after early compile errors. https://github.com/rescript-lang/rescript/pull/8408
 - Fix formatting of trailing comments before `=` in let bindings. https://github.com/rescript-lang/rescript/pull/8444
+- Fix namespaced reference lookup in editor analysis. https://github.com/rescript-lang/rescript/pull/8455
 
 # 12.3.0
 
diff --git a/analysis/src/Cmt.ml b/analysis/src/Cmt.ml
index ac1d5ae595f..72753b3040a 100644
--- a/analysis/src/Cmt.ml
+++ b/analysis/src/Cmt.ml
@@ -8,6 +8,32 @@ let fullForCmt ~moduleName ~package ~uri cmt =
     let extra = ProcessExtra.getExtra ~file ~infos in
     Some {file; extra; package}
 
+let fullForIncrementalCmt ~package ~moduleName ~uri =
+  if !Cfg.inIncrementalTypecheckingMode then
+    let path = Uri.toPath uri in
+    let incrementalCmtPath =
+      package.rootPath ^ "/lib/bs/___incremental" ^ "/" ^ moduleName
+      ^
+      match Files.classifySourceFile path with
+      | Resi -> ".cmti"
+      | _ -> ".cmt"
+    in
+    match fullForCmt ~moduleName ~package ~uri incrementalCmtPath with
+    | Some cmtInfo ->
+      if Debug.verbose () then
+        Printf.printf "[cmt] Found incremental cmt: %s\n"
+          (Filename.basename incrementalCmtPath);
+      Some cmtInfo
+    | None -> None
+  else None
+
+let fullFromModuleUri ~package ~moduleName ~uri ~paths =
+  match fullForIncrementalCmt ~package ~moduleName ~uri with
+  | Some cmtInfo -> Some cmtInfo
+  | None ->
+    let cmt = getCmtPath ~uri paths in
+    fullForCmt ~moduleName ~package ~uri cmt
+
 let fullFromUri ~uri =
   let path = Uri.toPath uri in
   match Packages.getPackage ~uri with
@@ -16,22 +42,8 @@ let fullFromUri ~uri =
     let moduleName =
       BuildSystem.namespacedName package.namespace (FindFiles.getName path)
     in
-    let incremental =
-      if !Cfg.inIncrementalTypecheckingMode then
-        let incrementalCmtPath =
-          package.rootPath ^ "/lib/bs/___incremental" ^ "/" ^ moduleName
-          ^
-          match Files.classifySourceFile path with
-          | Resi -> ".cmti"
-          | _ -> ".cmt"
-        in
-        fullForCmt ~moduleName ~package ~uri incrementalCmtPath
-      else None
-    in
-    match incremental with
-    | Some cmtInfo ->
-      if Debug.verbose () then Printf.printf "[cmt] Found incremental cmt\n";
-      Some cmtInfo
+    match fullForIncrementalCmt ~package ~moduleName ~uri with
+    | Some cmtInfo -> Some cmtInfo
     | None -> (
       match Hashtbl.find_opt package.pathsForModule moduleName with
       | Some paths ->
@@ -41,12 +53,20 @@ let fullFromUri ~uri =
         prerr_endline ("can't find module " ^ moduleName);
         None))
 
+let fullFromModule ~package ~moduleName =
+  Option.bind (Hashtbl.find_opt package.pathsForModule moduleName)
+  @@ fun paths ->
+  let uri = getUri paths in
+  fullFromModuleUri ~package ~moduleName ~uri ~paths
+
 let fullsFromModule ~package ~moduleName =
-  if Hashtbl.mem package.pathsForModule moduleName then
-    let paths = Hashtbl.find package.pathsForModule moduleName in
+  match Hashtbl.find_opt package.pathsForModule moduleName with
+  | None -> []
+  | Some paths ->
     let uris = getUris paths in
-    uris |> List.filter_map (fun uri -> fullFromUri ~uri)
-  else []
+    uris
+    |> List.filter_map (fun uri ->
+           fullFromModuleUri ~package ~moduleName ~uri ~paths)
 
 let loadFullCmtFromPath ~path =
   let uri = Uri.fromPath path in
diff --git a/analysis/src/References.ml b/analysis/src/References.ml
index e047a2ba182..142cbfa2f89 100644
--- a/analysis/src/References.ml
+++ b/analysis/src/References.ml
@@ -18,6 +18,20 @@ let locItemsForPos ~extra pos =
 
 let lineColToCmtLoc ~pos:(line, col) = (line + 1, col)
 
+(** External references in namespaced projects are indexed by the public
+  * namespace path, e.g. MyNamespace.MyModule1.myFunc1, while definitions live
+  * in hidden compiled modules like MyModule1-MyNamespace.
+  * We return the lookup key pair used by the external reference index.
+  *)
+let normalizeExternalReferenceKey ~namespace ~moduleName ~path =
+  match namespace with
+  | Some namespace when Utils.endsWith moduleName ("-" ^ namespace) ->
+    let suffixLen = String.length namespace + 1 in
+    let sourceModuleLen = String.length moduleName - suffixLen in
+    let sourceModule = String.sub moduleName 0 sourceModuleLen in
+    (namespace, sourceModule :: path)
+  | _ -> (moduleName, path)
+
 let getLocItem ~full ~pos ~debug =
   let log n msg = if debug then Printf.printf "getLocItem #%d: %s\n" n msg in
   let pos = lineColToCmtLoc ~pos in
@@ -485,6 +499,10 @@ let forLocalStamp ~full:{file; extra; package} stamp (tip : Tip.t) =
             in
             maybeLog ("Now checking path " ^ pathToString path);
             let thisModuleName = file.moduleName in
+            let normalizedModuleName, normalizedPath =
+              normalizeExternalReferenceKey ~namespace:package.namespace
+                ~moduleName:thisModuleName ~path
+            in
             let externals =
               package.projectFiles |> FileSet.elements
               |> List.filter (fun name -> name <> file.moduleName)
@@ -493,14 +511,15 @@ let forLocalStamp ~full:{file; extra; package} stamp (tip : Tip.t) =
                      |> List.map (fun {file; extra} ->
                             match
                               Hashtbl.find_opt extra.externalReferences
-                                thisModuleName
+                                normalizedModuleName
                             with
                             | None -> []
                             | Some refs ->
                               let locs =
                                 refs
                                 |> Utils.filterMap (fun (p, t, locs) ->
-                                       if p = path && t = tip then Some locs
+                                       if p = normalizedPath && t = tip then
+                                         Some locs
                                        else None)
                               in
                               locs
@@ -522,10 +541,8 @@ let allReferencesForLocItem ~full:({file; package} as full) locItem =
   | TopLevelModule moduleName ->
     let otherModulesReferences =
       package.projectFiles |> FileSet.elements
-      |> Utils.filterMap (fun name ->
-             match ProcessCmt.fileForModule ~package name with
-             | None -> None
-             | Some file -> Cmt.fullFromUri ~uri:file.uri)
+      |> Utils.filterMap (fun moduleName ->
+             Cmt.fullFromModule ~package ~moduleName)
       |> List.map (fun full ->
              match Hashtbl.find_opt full.extra.fileReferences moduleName with
              | None -> []
@@ -563,7 +580,7 @@ let allReferencesForLocItem ~full:({file; package} as full) locItem =
       match exportedForTip ~env ~path ~package ~tip with
       | None -> []
       | Some (env, _name, stamp) -> (
-        match Cmt.fullFromUri ~uri:env.file.uri with
+        match Cmt.fullFromModule ~package ~moduleName:env.file.moduleName with
         | None -> []
         | Some full ->
           maybeLog
diff --git a/tests/analysis_tests/Makefile b/tests/analysis_tests/Makefile
index 0fd0226e6a0..741c90403ec 100644
--- a/tests/analysis_tests/Makefile
+++ b/tests/analysis_tests/Makefile
@@ -4,6 +4,7 @@ test-analysis-binary:
 	make -C tests test
 	make -C tests-generic-jsx-transform test
 	make -C tests-incremental-typechecking test
+	make -C tests-namespaced-references test
 	make -C tests-sourcedirs-dependency test
 
 test-reanalyze:
@@ -15,6 +16,7 @@ clean:
 	make -C tests clean
 	make -C tests-generic-jsx-transform clean
 	make -C tests-incremental-typechecking clean
+	make -C tests-namespaced-references clean
 	make -C tests-sourcedirs-dependency clean
 	make -C tests-reanalyze clean
 
diff --git a/tests/analysis_tests/tests-namespaced-references/.gitignore b/tests/analysis_tests/tests-namespaced-references/.gitignore
new file mode 100644
index 00000000000..3b4e8dcf930
--- /dev/null
+++ b/tests/analysis_tests/tests-namespaced-references/.gitignore
@@ -0,0 +1,2 @@
+lib/
+node_modules/
diff --git a/tests/analysis_tests/tests-namespaced-references/Makefile b/tests/analysis_tests/tests-namespaced-references/Makefile
new file mode 100644
index 00000000000..2b663dd3475
--- /dev/null
+++ b/tests/analysis_tests/tests-namespaced-references/Makefile
@@ -0,0 +1,20 @@
+SHELL = /bin/bash
+
+build:
+	yarn build
+
+	# Simulate editor-written incremental CMTs
+	mkdir -p lib/bs/___incremental
+	cp lib/bs/src/MyModule1-MyNamespace.cmt lib/bs/___incremental/MyModule1-MyNamespace.cmt
+	cp lib/bs/src/MyModule2-MyNamespace.cmt lib/bs/___incremental/MyModule2-MyNamespace.cmt
+	cp lib/bs/MyNamespace.cmt lib/bs/___incremental/MyNamespace.cmt
+
+test: build
+	./test.sh
+
+clean:
+	yarn clean
+
+.DEFAULT_GOAL := test
+
+.PHONY: build clean test
diff --git a/tests/analysis_tests/tests-namespaced-references/package.json b/tests/analysis_tests/tests-namespaced-references/package.json
new file mode 100644
index 00000000000..596b324a429
--- /dev/null
+++ b/tests/analysis_tests/tests-namespaced-references/package.json
@@ -0,0 +1,11 @@
+{
+  "name": "@tests/namespaced-references",
+  "private": true,
+  "scripts": {
+    "build": "rescript build",
+    "clean": "rescript clean"
+  },
+  "dependencies": {
+    "rescript": "workspace:^"
+  }
+}
diff --git a/tests/analysis_tests/tests-namespaced-references/rescript.json b/tests/analysis_tests/tests-namespaced-references/rescript.json
new file mode 100644
index 00000000000..283f6934730
--- /dev/null
+++ b/tests/analysis_tests/tests-namespaced-references/rescript.json
@@ -0,0 +1,17 @@
+{
+  "name": "@tests/namespaced-references",
+  "namespace": "my-namespace",
+  "sources": [
+    {
+      "dir": "src",
+      "subdirs": true
+    }
+  ],
+  "package-specs": [
+    {
+      "module": "commonjs",
+      "in-source": false
+    }
+  ],
+  "suffix": ".res.js"
+}
diff --git a/tests/analysis_tests/tests-namespaced-references/src/MyModule1.res b/tests/analysis_tests/tests-namespaced-references/src/MyModule1.res
new file mode 100644
index 00000000000..d51b53b56f4
--- /dev/null
+++ b/tests/analysis_tests/tests-namespaced-references/src/MyModule1.res
@@ -0,0 +1,6 @@
+// ^in+
+// ^dv+
+let myFunc1 = () => MyModule2.myFunc2()
+//                            ^ref
+// ^dv-
+// ^in-
diff --git a/tests/analysis_tests/tests-namespaced-references/src/MyModule2.res b/tests/analysis_tests/tests-namespaced-references/src/MyModule2.res
new file mode 100644
index 00000000000..4e7d3930e1e
--- /dev/null
+++ b/tests/analysis_tests/tests-namespaced-references/src/MyModule2.res
@@ -0,0 +1,2 @@
+let myFunc2 = () => 42
+//  ^ref
diff --git a/tests/analysis_tests/tests-namespaced-references/src/expected/MyModule1.res.txt b/tests/analysis_tests/tests-namespaced-references/src/expected/MyModule1.res.txt
new file mode 100644
index 00000000000..ba415fdf9d3
--- /dev/null
+++ b/tests/analysis_tests/tests-namespaced-references/src/expected/MyModule1.res.txt
@@ -0,0 +1,9 @@
+References src/MyModule1.res 2:30
+[cmt] Found incremental cmt: MyModule1-MyNamespace.cmt
+[cmt] Found incremental cmt: MyModule2-MyNamespace.cmt
+[cmt] Found incremental cmt: MyModule1-MyNamespace.cmt
+[cmt] Found incremental cmt: MyNamespace.cmt
+[
+{"uri": "MyModule1.res", "range": {"start": {"line": 2, "character": 30}, "end": {"line": 2, "character": 37}}},
+{"uri": "MyModule2.res", "range": {"start": {"line": 0, "character": 4}, "end": {"line": 0, "character": 11}}}
+]
diff --git a/tests/analysis_tests/tests-namespaced-references/src/expected/MyModule2.res.txt b/tests/analysis_tests/tests-namespaced-references/src/expected/MyModule2.res.txt
new file mode 100644
index 00000000000..9a42ce08712
--- /dev/null
+++ b/tests/analysis_tests/tests-namespaced-references/src/expected/MyModule2.res.txt
@@ -0,0 +1,5 @@
+References src/MyModule2.res 0:4
+[
+{"uri": "MyModule1.res", "range": {"start": {"line": 2, "character": 30}, "end": {"line": 2, "character": 37}}},
+{"uri": "MyModule2.res", "range": {"start": {"line": 0, "character": 4}, "end": {"line": 0, "character": 11}}}
+]
diff --git a/tests/analysis_tests/tests-namespaced-references/test.sh b/tests/analysis_tests/tests-namespaced-references/test.sh
new file mode 100755
index 00000000000..32801fb411f
--- /dev/null
+++ b/tests/analysis_tests/tests-namespaced-references/test.sh
@@ -0,0 +1,30 @@
+for file in src/*.res; do
+  output="$(dirname $file)/expected/$(basename $file).txt"
+  ../../../_build/install/default/bin/rescript-editor-analysis test $file &> $output
+  # CI. We use LF, and the CI OCaml fork prints CRLF. Convert.
+  if [ "$RUNNER_OS" == "Windows" ]; then
+    perl -pi -e 's/\r\n/\n/g' -- $output
+  fi
+
+  # Remove unwanted output (machine-specific path)
+  perl -ni -e 'print unless /^\[getRuntimeDir\]/' -- $output
+
+  # Strip leading newlines caused by ^in+ and ^dv+ marker usage.
+  perl -0pi -e 's/\A\n+//' -- $output
+
+  # Strip trailing newlines caused by ^dv- and ^in- marker usage.
+  perl -0pi -e 's/\n+\z/\n/' -- $output
+done
+
+warningYellow='\033[0;33m'
+successGreen='\033[0;32m'
+reset='\033[0m'
+
+diff=$(git ls-files --modified src/expected)
+if [[ $diff = "" ]]; then
+  printf "${successGreen}✅ No unstaged tests difference.${reset}\n"
+else
+  printf "${warningYellow}⚠️ There are unstaged differences in tests/! Did you break a test?\n${diff}\n${reset}"
+  git --no-pager diff src/expected
+  exit 1
+fi
diff --git a/tests/ounit_tests/ounit_analysis_references_tests.ml b/tests/ounit_tests/ounit_analysis_references_tests.ml
new file mode 100644
index 00000000000..a81e69764e1
--- /dev/null
+++ b/tests/ounit_tests/ounit_analysis_references_tests.ml
@@ -0,0 +1,25 @@
+open OUnit
+
+let show_reference (module_name, path) =
+  Printf.sprintf "%s:%s" module_name (String.concat "." path)
+
+let assert_ref_key_eq ~expected ~actual =
+  assert_equal ~printer:show_reference expected actual
+
+let suites =
+  __FILE__
+  >::: [
+         ( "without namespace, external reference is unchanged" >:: fun _ ->
+           assert_ref_key_eq ~expected:("MyModule2", ["myFunc2"])
+             ~actual:
+               (Analysis.References.normalizeExternalReferenceKey
+                  ~namespace:None ~moduleName:"MyModule2" ~path:["myFunc2"]) );
+         ( "with namespace, hidden module resolves to public namespace path"
+         >:: fun _ ->
+           assert_ref_key_eq
+             ~expected:("MyNamespace", ["MyModule2"; "myFunc2"])
+             ~actual:
+               (Analysis.References.normalizeExternalReferenceKey
+                  ~namespace:(Some "MyNamespace")
+                  ~moduleName:"MyModule2-MyNamespace" ~path:["myFunc2"]) );
+       ]
diff --git a/tests/ounit_tests/ounit_tests_main.ml b/tests/ounit_tests/ounit_tests_main.ml
index ee39b4a37f3..f5a676e5fa8 100644
--- a/tests/ounit_tests/ounit_tests_main.ml
+++ b/tests/ounit_tests/ounit_tests_main.ml
@@ -22,6 +22,7 @@ let suites =
       Ounit_bsb_pkg_tests.suites;
       Ounit_util_tests.suites;
       Ounit_jsx_loc_tests.suites;
+      Ounit_analysis_references_tests.suites;
     ]
 
 let _ = OUnit.run_test_tt_main suites
diff --git a/yarn.lock b/yarn.lock
index 64582a26b57..2f447e924d1 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -773,6 +773,14 @@ __metadata:
   languageName: unknown
   linkType: soft
 
+"@tests/namespaced-references@workspace:tests/analysis_tests/tests-namespaced-references":
+  version: 0.0.0-use.local
+  resolution: "@tests/namespaced-references@workspace:tests/analysis_tests/tests-namespaced-references"
+  dependencies:
+    rescript: "workspace:^"
+  languageName: unknown
+  linkType: soft
+
 "@tests/reanalyze-benchmark@workspace:tests/analysis_tests/tests-reanalyze/deadcode-benchmark":
   version: 0.0.0-use.local
   resolution: "@tests/reanalyze-benchmark@workspace:tests/analysis_tests/tests-reanalyze/deadcode-benchmark"

From 5e11d18a4cd948705b7d4c1af426e5f9ce97a5db Mon Sep 17 00:00:00 2001
From: Nathan Tranquilla <n1tranquilla@gmail.com>
Date: Wed, 19 Aug 2026 11:20:26 +0200
Subject: [PATCH 04/10] Fix build crash when compiler output is not valid UTF-8
 (#8482)

Adapted from 7f15521f2337ce338d536ab206ae6718a9d41873 for the 12.3.x Rewatch test layout.
---
 CHANGELOG.md                 |  1 +
 rewatch/src/build/compile.rs | 23 ++++++++++++++++++++---
 2 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index d0e49fcf8d2..f733c87f50b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -17,6 +17,7 @@
 - Fix rewatch warning replay after early compile errors. https://github.com/rescript-lang/rescript/pull/8408
 - Fix formatting of trailing comments before `=` in let bindings. https://github.com/rescript-lang/rescript/pull/8444
 - Fix namespaced reference lookup in editor analysis. https://github.com/rescript-lang/rescript/pull/8455
+- Fix build crash when the compiler emits output that is not valid UTF-8, such as a truncated multibyte character in a code frame. https://github.com/rescript-lang/rescript/pull/8482
 
 # 12.3.0
 
diff --git a/rewatch/src/build/compile.rs b/rewatch/src/build/compile.rs
index 827bc322e59..2aa4c264a15 100644
--- a/rewatch/src/build/compile.rs
+++ b/rewatch/src/build/compile.rs
@@ -21,6 +21,12 @@ use std::process::Command;
 use std::sync::OnceLock;
 use std::time::SystemTime;
 
+/// Decode captured compiler output without crashing if a code frame truncates a
+/// multi-byte character.
+fn compiler_output_to_string(bytes: &[u8]) -> String {
+    String::from_utf8_lossy(bytes).to_string()
+}
+
 /// Execute js-post-build command for a compiled JavaScript file.
 /// The command runs in the directory containing the rescript.json that defines it.
 /// The absolute path to the JS file is passed as an argument.
@@ -789,9 +795,7 @@ fn compile_file(
             "Could not compile file. Error: {e}. Path to AST: {ast_path:?}"
         )),
         Ok(x) => {
-            let err = std::str::from_utf8(&x.stderr)
-                .expect("stdout should be non-null")
-                .to_string();
+            let err = compiler_output_to_string(&x.stderr);
 
             let dir = Path::new(implementation_file_path).parent().unwrap();
 
@@ -962,6 +966,19 @@ pub fn mark_modules_with_deleted_deps_dirty(build_state: &mut BuildState) {
     });
 }
 
+#[cfg(test)]
+mod tests {
+    use super::compiler_output_to_string;
+
+    #[test]
+    fn compiler_output_to_string_handles_invalid_utf8() {
+        // Start of an em dash (U+2014), with its third byte missing.
+        let truncated = [b'W', b'a', b'r', b'n', b'i', b'n', b'g', b' ', 0xe2, 0x80];
+        let decoded = compiler_output_to_string(&truncated);
+        assert!(decoded.starts_with("Warning "));
+    }
+}
+
 // this happens when a compile is not completed successfully in some way
 // a dependent module could be compiled with a new interface, but the dependent
 // modules have not finished compiling. This can cause a stale build.

From d0c1f42e0bbce61b3e451d4273e1155cddacd6d6 Mon Sep 17 00:00:00 2001
From: Florian Hammerschmidt <florianh89@gmail.com>
Date: Mon, 27 Jul 2026 16:27:33 +0200
Subject: [PATCH 05/10] Preserve multibyte characters when wrapping long source
 lines (#8520)

* Preserve multibyte characters when wrapping long source lines in compiler code frames

* Changelog
---
 CHANGELOG.md                         |  1 +
 compiler/ml/code_frame.ml            | 19 ++++++++++++++-----
 tests/ounit_tests/ounit_utf8_test.ml |  3 +++
 3 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index f733c87f50b..335c0bdb1c4 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -18,6 +18,7 @@
 - Fix formatting of trailing comments before `=` in let bindings. https://github.com/rescript-lang/rescript/pull/8444
 - Fix namespaced reference lookup in editor analysis. https://github.com/rescript-lang/rescript/pull/8455
 - Fix build crash when the compiler emits output that is not valid UTF-8, such as a truncated multibyte character in a code frame. https://github.com/rescript-lang/rescript/pull/8482
+- Preserve multibyte characters when wrapping long source lines in compiler code frames. https://github.com/rescript-lang/rescript/pull/8520
 
 # 12.3.0
 
diff --git a/compiler/ml/code_frame.ml b/compiler/ml/code_frame.ml
index 9f75c765ac4..b14b7007af9 100644
--- a/compiler/ml/code_frame.ml
+++ b/compiler/ml/code_frame.ml
@@ -37,14 +37,23 @@ let leading_space_count str =
   loop 0 0
 
 let break_long_line max_width line =
+  let line_length = String.length line in
+  let rec find_chunk_end pos remaining_width =
+    if pos = line_length || remaining_width = 0 then pos
+    else
+      let char_length =
+        String.get_utf_8_uchar line pos |> Uchar.utf_decode_length
+      in
+      find_chunk_end (pos + char_length) (remaining_width - 1)
+  in
   let rec loop pos accum =
-    if pos = String.length line then accum
+    if pos = line_length then List.rev accum
     else
-      let chunk_length = min max_width (String.length line - pos) in
-      let chunk = String.sub line pos chunk_length in
-      loop (pos + chunk_length) (chunk :: accum)
+      let chunk_end = find_chunk_end pos max_width in
+      let chunk = String.sub line pos (chunk_end - pos) in
+      loop chunk_end (chunk :: accum)
   in
-  loop 0 [] |> List.rev
+  loop 0 []
 
 let filter_mapi f l =
   let rec loop f l i accum =
diff --git a/tests/ounit_tests/ounit_utf8_test.ml b/tests/ounit_tests/ounit_utf8_test.ml
index 42846b6d049..b94babc4ea1 100644
--- a/tests/ounit_tests/ounit_utf8_test.ml
+++ b/tests/ounit_tests/ounit_utf8_test.ml
@@ -4,6 +4,7 @@
 let ( >:: ), ( >::: ) = OUnit.(( >:: ), ( >::: ))
 
 let ( =~ ) = OUnit.assert_equal
+
 let suites =
   __FILE__
   >::: [
@@ -29,4 +30,6 @@ let suites =
                 105;
               ] );
          (__LOC__ >:: fun _ -> Ext_utf8.decode_utf8_string "" =~ []);
+         ( __LOC__ >:: fun _ ->
+           Code_frame.break_long_line 4 "abc—def" =~ ["abc—"; "def"] );
        ]

From b69ed1bd2dfa0ae2a83fc89fc22240569bac2110 Mon Sep 17 00:00:00 2001
From: Christoph Knittel <ck@cca.io>
Date: Sat, 15 Aug 2026 13:28:37 +0200
Subject: [PATCH 06/10] Fix exponentiation precedence for compound exponents
 (#8550)

* Fix exponentiation right operand precedence

Signed-off-by: Christoph Knittel <ck@cca.io>

* Update changelog for exponentiation precedence fix

Signed-off-by: Christoph Knittel <ck@cca.io>

---------

Signed-off-by: Christoph Knittel <ck@cca.io>
---
 CHANGELOG.md                            |  1 +
 compiler/core/js_op_util.ml             |  2 +-
 tests/tests/src/exponentiation_test.mjs | 48 ++++++++++++++++++-------
 tests/tests/src/exponentiation_test.res | 11 ++++++
 4 files changed, 49 insertions(+), 13 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 335c0bdb1c4..c83d6972079 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -19,6 +19,7 @@
 - Fix namespaced reference lookup in editor analysis. https://github.com/rescript-lang/rescript/pull/8455
 - Fix build crash when the compiler emits output that is not valid UTF-8, such as a truncated multibyte character in a code frame. https://github.com/rescript-lang/rescript/pull/8482
 - Preserve multibyte characters when wrapping long source lines in compiler code frames. https://github.com/rescript-lang/rescript/pull/8520
+- Preserve parentheses around multiplication, division, and modulo expressions used as exponents. https://github.com/rescript-lang/rescript/pull/8550
 
 # 12.3.0
 
diff --git a/compiler/core/js_op_util.ml b/compiler/core/js_op_util.ml
index 8d2d8636396..1ac99090215 100644
--- a/compiler/core/js_op_util.ml
+++ b/compiler/core/js_op_util.ml
@@ -41,7 +41,7 @@ let op_prec (op : Js_op.binop) =
   | Lsl | Lsr | Asr -> (10, 10, 11)
   | Bnot | Plus | Minus -> (11, 11, 12)
   | Mul | Div | Mod -> (12, 12, 13)
-  | Pow -> (13, 14, 12)
+  | Pow -> (13, 14, 13)
 
 let op_int_prec (op : Js_op.int_op) =
   match op with
diff --git a/tests/tests/src/exponentiation_test.mjs b/tests/tests/src/exponentiation_test.mjs
index c39ea9465db..debb6adbc00 100644
--- a/tests/tests/src/exponentiation_test.mjs
+++ b/tests/tests/src/exponentiation_test.mjs
@@ -7,25 +7,49 @@ let intPow = ((a, b) => Math.pow(a, b) | 0);
 
 let four = 4;
 
+function floatPowDiv(base, numerator, denominator) {
+  return base ** (numerator / denominator);
+}
+
+function floatPowMul(base, left, right) {
+  return base ** (left * right);
+}
+
+function floatPowMod(base, value, modulus) {
+  return base ** (value % modulus);
+}
+
+function bigintPowMul(base, left, right) {
+  return base ** (left * right);
+}
+
 Mocha.describe("Exponentiation_test", () => {
   Mocha.test("exponentiation operations", () => {
-    Test_utils.eq("File \"exponentiation_test.res\", line 11, characters 7-14", 2 ** 3 ** 2, Math.pow(2, Math.pow(3, 2)));
-    Test_utils.eq("File \"exponentiation_test.res\", line 12, characters 7-14", 2 ** (-3) ** 2, Math.pow(2, Math.pow(-3, 2)));
-    Test_utils.eq("File \"exponentiation_test.res\", line 13, characters 7-14", (2 ** 3) ** 2, Math.pow(Math.pow(2, 3), 2));
-    Test_utils.eq("File \"exponentiation_test.res\", line 14, characters 7-14", (-2) ** 2, Math.pow(-2, 2));
-    Test_utils.eq("File \"exponentiation_test.res\", line 16, characters 7-14", 512, intPow(2, intPow(3, 2)));
-    Test_utils.eq("File \"exponentiation_test.res\", line 17, characters 7-14", 512, intPow(2, intPow(-3, 2)));
-    Test_utils.eq("File \"exponentiation_test.res\", line 18, characters 7-14", 64, intPow(intPow(2, 3), 2));
-    Test_utils.eq("File \"exponentiation_test.res\", line 19, characters 7-14", -2147483648, intPow(-2, 31));
-    Test_utils.eq("File \"exponentiation_test.res\", line 20, characters 7-14", 0, intPow(2, 32));
-    Test_utils.eq("File \"exponentiation_test.res\", line 21, characters 7-14", 0, intPow(2147483647, 2));
-    Test_utils.eq("File \"exponentiation_test.res\", line 22, characters 7-14", 0, intPow(-2147483648, 2));
-    Test_utils.eq("File \"exponentiation_test.res\", line 24, characters 7-14", 256, four ** four | 0);
+    Test_utils.eq("File \"exponentiation_test.res\", line 17, characters 7-14", 2 ** 3 ** 2, Math.pow(2, Math.pow(3, 2)));
+    Test_utils.eq("File \"exponentiation_test.res\", line 18, characters 7-14", 2 ** (-3) ** 2, Math.pow(2, Math.pow(-3, 2)));
+    Test_utils.eq("File \"exponentiation_test.res\", line 19, characters 7-14", (2 ** 3) ** 2, Math.pow(Math.pow(2, 3), 2));
+    Test_utils.eq("File \"exponentiation_test.res\", line 20, characters 7-14", (-2) ** 2, Math.pow(-2, 2));
+    Test_utils.eq("File \"exponentiation_test.res\", line 22, characters 7-14", 512, intPow(2, intPow(3, 2)));
+    Test_utils.eq("File \"exponentiation_test.res\", line 23, characters 7-14", 512, intPow(2, intPow(-3, 2)));
+    Test_utils.eq("File \"exponentiation_test.res\", line 24, characters 7-14", 64, intPow(intPow(2, 3), 2));
+    Test_utils.eq("File \"exponentiation_test.res\", line 25, characters 7-14", -2147483648, intPow(-2, 31));
+    Test_utils.eq("File \"exponentiation_test.res\", line 26, characters 7-14", 0, intPow(2, 32));
+    Test_utils.eq("File \"exponentiation_test.res\", line 27, characters 7-14", 0, intPow(2147483647, 2));
+    Test_utils.eq("File \"exponentiation_test.res\", line 28, characters 7-14", 0, intPow(-2147483648, 2));
+    Test_utils.eq("File \"exponentiation_test.res\", line 30, characters 7-14", 256, four ** four | 0);
+    Test_utils.eq("File \"exponentiation_test.res\", line 32, characters 7-14", 2 ** (0 / 10000), 1);
+    Test_utils.eq("File \"exponentiation_test.res\", line 33, characters 7-14", 2 ** (3 * 4), 4096);
+    Test_utils.eq("File \"exponentiation_test.res\", line 34, characters 7-14", 2 ** (5 % 3), 4);
+    Test_utils.eq("File \"exponentiation_test.res\", line 35, characters 7-14", 2n ** (3n * 2n), 64n);
   });
 });
 
 export {
   intPow,
   four,
+  floatPowDiv,
+  floatPowMul,
+  floatPowMod,
+  bigintPowMul,
 }
 /*  Not a pure module */
diff --git a/tests/tests/src/exponentiation_test.res b/tests/tests/src/exponentiation_test.res
index 19fb9cb7b44..216de749954 100644
--- a/tests/tests/src/exponentiation_test.res
+++ b/tests/tests/src/exponentiation_test.res
@@ -6,6 +6,12 @@ external jsPow: (float, float) => float = "Math.pow"
 let intPow: (int, int) => int = %raw(`(a, b) => Math.pow(a, b) | 0`)
 let four: int = %raw(`4`)
 
+let floatPowDiv = (base: float, numerator: float, denominator: float) =>
+  base ** (numerator /. denominator)
+let floatPowMul = (base: float, left: float, right: float) => base ** (left *. right)
+let floatPowMod = (base: float, value: float, modulus: float) => base ** (value % modulus)
+let bigintPowMul = (base: bigint, left: bigint, right: bigint) => base ** (left * right)
+
 describe(__MODULE__, () => {
   test("exponentiation operations", () => {
     eq(__LOC__, 2. ** 3. ** 2., jsPow(2., jsPow(3., 2.)))
@@ -22,5 +28,10 @@ describe(__MODULE__, () => {
     eq(__LOC__, -2147483648 ** 2, intPow(-2147483648, 2))
 
     eq(__LOC__, 4 ** 4, four ** four)
+
+    eq(__LOC__, floatPowDiv(2., 0., 10000.), 1.)
+    eq(__LOC__, floatPowMul(2., 3., 4.), 4096.)
+    eq(__LOC__, floatPowMod(2., 5., 3.), 4.)
+    eq(__LOC__, bigintPowMul(2n, 3n, 2n), 64n)
   })
 })

From 05f816982dcc3e070477f1b0da30cfc56fad41f4 Mon Sep 17 00:00:00 2001
From: Cristiano Calcagno <cristianoc@users.noreply.github.com>
Date: Wed, 19 Aug 2026 12:47:08 +0200
Subject: [PATCH 07/10] Enforce function arity in inclusion, type equality, and
 coercion (#8559)

Backport only the three type-system guards and focused regressions from 8fafaf916de17925afa3a20e42673f0b5bbbeaf7; omit the larger diagnostic-reporting refactor.
---
 CHANGELOG.md                                  |  1 +
 compiler/ml/ctype.ml                          | 12 ++++----
 .../coercion_arity_mismatch.res.expected      |  9 ++++++
 ...dule_sig_value_arity_mismatch.res.expected | 28 +++++++++++++++++++
 ..._decl_function_arity_mismatch.res.expected | 28 +++++++++++++++++++
 .../fixtures/coercion_arity_mismatch.res      |  2 ++
 .../module_sig_value_arity_mismatch.res       |  5 ++++
 .../type_decl_function_arity_mismatch.res     |  5 ++++
 8 files changed, 84 insertions(+), 6 deletions(-)
 create mode 100644 tests/build_tests/super_errors/expected/coercion_arity_mismatch.res.expected
 create mode 100644 tests/build_tests/super_errors/expected/module_sig_value_arity_mismatch.res.expected
 create mode 100644 tests/build_tests/super_errors/expected/type_decl_function_arity_mismatch.res.expected
 create mode 100644 tests/build_tests/super_errors/fixtures/coercion_arity_mismatch.res
 create mode 100644 tests/build_tests/super_errors/fixtures/module_sig_value_arity_mismatch.res
 create mode 100644 tests/build_tests/super_errors/fixtures/type_decl_function_arity_mismatch.res

diff --git a/CHANGELOG.md b/CHANGELOG.md
index c83d6972079..687ba0584de 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -20,6 +20,7 @@
 - Fix build crash when the compiler emits output that is not valid UTF-8, such as a truncated multibyte character in a code frame. https://github.com/rescript-lang/rescript/pull/8482
 - Preserve multibyte characters when wrapping long source lines in compiler code frames. https://github.com/rescript-lang/rescript/pull/8520
 - Preserve parentheses around multiplication, division, and modulo expressions used as exponents. https://github.com/rescript-lang/rescript/pull/8550
+- Enforce function arity in interface/module inclusion, type equality, and coercion. https://github.com/rescript-lang/rescript/pull/8559
 
 # 12.3.0
 
diff --git a/compiler/ml/ctype.ml b/compiler/ml/ctype.ml
index e15adf31b43..23c95d03394 100644
--- a/compiler/ml/ctype.ml
+++ b/compiler/ml/ctype.ml
@@ -2914,8 +2914,8 @@ let rec moregen inst_nongen type_pairs env t1 t2 =
               | Tvar _, _ when may_instantiate inst_nongen t1' ->
                 moregen_occur env t1'.level t2;
                 link_type t1' t2
-              | Tarrow (arg1, ret1, _, _), Tarrow (arg2, ret2, _, _)
-                when Asttypes.same_arg_label arg1.lbl arg2.lbl ->
+              | Tarrow (arg1, ret1, _, a1), Tarrow (arg2, ret2, _, a2)
+                when a1 = a2 && Asttypes.same_arg_label arg1.lbl arg2.lbl ->
                 moregen inst_nongen type_pairs env arg1.typ arg2.typ;
                 moregen inst_nongen type_pairs env ret1 ret2
               | Ttuple tl1, Ttuple tl2 ->
@@ -3184,8 +3184,8 @@ let rec eqtype rename type_pairs subst env t1 t2 =
                   if List.exists (fun (_, t) -> t == t2') !subst then
                     raise (Unify []);
                   subst := (t1', t2') :: !subst)
-              | Tarrow (arg1, ret1, _, _), Tarrow (arg2, ret2, _, _)
-                when Asttypes.same_arg_label arg1.lbl arg2.lbl ->
+              | Tarrow (arg1, ret1, _, a1), Tarrow (arg2, ret2, _, a2)
+                when a1 = a2 && Asttypes.same_arg_label arg1.lbl arg2.lbl ->
                 eqtype rename type_pairs subst env arg1.typ arg2.typ;
                 eqtype rename type_pairs subst env ret1 ret2
               | Ttuple tl1, Ttuple tl2 ->
@@ -3597,8 +3597,8 @@ let rec subtype_rec env trace t1 t2 cstrs =
       TypePairs.add subtypes (t1, t2) ();
       match (t1.desc, t2.desc) with
       | Tvar _, _ | _, Tvar _ -> (trace, t1, t2, !univar_pairs, None) :: cstrs
-      | Tarrow (arg1, ret1, _, _), Tarrow (arg2, ret2, _, _)
-        when Asttypes.same_arg_label arg1.lbl arg2.lbl ->
+      | Tarrow (arg1, ret1, _, a1), Tarrow (arg2, ret2, _, a2)
+        when a1 = a2 && Asttypes.same_arg_label arg1.lbl arg2.lbl ->
         let cstrs =
           subtype_rec env
             ((arg2.typ, arg1.typ) :: trace)
diff --git a/tests/build_tests/super_errors/expected/coercion_arity_mismatch.res.expected b/tests/build_tests/super_errors/expected/coercion_arity_mismatch.res.expected
new file mode 100644
index 00000000000..6fd77c58aa4
--- /dev/null
+++ b/tests/build_tests/super_errors/expected/coercion_arity_mismatch.res.expected
@@ -0,0 +1,9 @@
+
+  We've found a bug for you!
+  /.../fixtures/coercion_arity_mismatch.res:2:10-31
+
+  1 │ let f = (x: int) => (y: int) => x + y
+  2 │ let g = (f :> (int, int) => int)
+  3 │ 
+
+  Type int => int => int is not a subtype of (int, int) => int
\ No newline at end of file
diff --git a/tests/build_tests/super_errors/expected/module_sig_value_arity_mismatch.res.expected b/tests/build_tests/super_errors/expected/module_sig_value_arity_mismatch.res.expected
new file mode 100644
index 00000000000..f491e37f771
--- /dev/null
+++ b/tests/build_tests/super_errors/expected/module_sig_value_arity_mismatch.res.expected
@@ -0,0 +1,28 @@
+
+  We've found a bug for you!
+  /.../fixtures/module_sig_value_arity_mismatch.res:3:5-5:1
+
+  1 │ module M: {
+  2 │   let f: (int, int) => int
+  3 │ } = {
+  4 │   let f = (x: int) => (y: int) => x + y
+  5 │ }
+  6 │ 
+
+  Signature mismatch:
+  Modules do not match:
+    {
+  let f: int => int => int
+}
+  is not included in
+    {
+  let f: (int, int) => int
+}
+  Values do not match:
+    let f: int => int => int
+  is not included in
+    let f: (int, int) => int
+  /.../fixtures/module_sig_value_arity_mismatch.res:2:3-26:
+    Expected declaration
+  /.../fixtures/module_sig_value_arity_mismatch.res:4:7:
+    Actual declaration
\ No newline at end of file
diff --git a/tests/build_tests/super_errors/expected/type_decl_function_arity_mismatch.res.expected b/tests/build_tests/super_errors/expected/type_decl_function_arity_mismatch.res.expected
new file mode 100644
index 00000000000..14e91bcf247
--- /dev/null
+++ b/tests/build_tests/super_errors/expected/type_decl_function_arity_mismatch.res.expected
@@ -0,0 +1,28 @@
+
+  We've found a bug for you!
+  /.../fixtures/type_decl_function_arity_mismatch.res:3:5-5:1
+
+  1 │ module M: {
+  2 │   type t = (int, int) => int
+  3 │ } = {
+  4 │   type t = int => int => int
+  5 │ }
+  6 │ 
+
+  Signature mismatch:
+  Modules do not match:
+    {
+  type t = int => int => int
+}
+  is not included in
+    {
+  type t = (int, int) => int
+}
+  Type declarations do not match:
+    type t = int => int => int
+  is not included in
+    type t = (int, int) => int
+  /.../fixtures/type_decl_function_arity_mismatch.res:2:3-28:
+    Expected declaration
+  /.../fixtures/type_decl_function_arity_mismatch.res:4:3-28:
+    Actual declaration
\ No newline at end of file
diff --git a/tests/build_tests/super_errors/fixtures/coercion_arity_mismatch.res b/tests/build_tests/super_errors/fixtures/coercion_arity_mismatch.res
new file mode 100644
index 00000000000..93d9111360e
--- /dev/null
+++ b/tests/build_tests/super_errors/fixtures/coercion_arity_mismatch.res
@@ -0,0 +1,2 @@
+let f = (x: int) => (y: int) => x + y
+let g = (f :> (int, int) => int)
diff --git a/tests/build_tests/super_errors/fixtures/module_sig_value_arity_mismatch.res b/tests/build_tests/super_errors/fixtures/module_sig_value_arity_mismatch.res
new file mode 100644
index 00000000000..a335585ac0a
--- /dev/null
+++ b/tests/build_tests/super_errors/fixtures/module_sig_value_arity_mismatch.res
@@ -0,0 +1,5 @@
+module M: {
+  let f: (int, int) => int
+} = {
+  let f = (x: int) => (y: int) => x + y
+}
diff --git a/tests/build_tests/super_errors/fixtures/type_decl_function_arity_mismatch.res b/tests/build_tests/super_errors/fixtures/type_decl_function_arity_mismatch.res
new file mode 100644
index 00000000000..4a831f446dd
--- /dev/null
+++ b/tests/build_tests/super_errors/fixtures/type_decl_function_arity_mismatch.res
@@ -0,0 +1,5 @@
+module M: {
+  type t = (int, int) => int
+} = {
+  type t = int => int => int
+}

From 1f2caf0fe8304d0212ede02de98a8bc446e611fe Mon Sep 17 00:00:00 2001
From: Cristiano Calcagno <cristianoc@users.noreply.github.com>
Date: Wed, 19 Aug 2026 12:48:18 +0200
Subject: [PATCH 08/10] Record arity for bare labeled arrow types (#8563)

Backport only the independent bare labeled-arrow fix from 110534a62abcd3cc24b70403351bfaaa7f96ce88; omit the broader external phantom-argument parser/printer rewrite.
---
 CHANGELOG.md                                     |  1 +
 compiler/syntax/src/res_core.ml                  |  2 +-
 .../errors/typexpr/expected/arrow.res.txt        |  2 +-
 .../grammar/typexpr/expected/es6Arrow.res.txt    | 16 ++++++++--------
 4 files changed, 11 insertions(+), 10 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 687ba0584de..1a47d36b4af 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -21,6 +21,7 @@
 - Preserve multibyte characters when wrapping long source lines in compiler code frames. https://github.com/rescript-lang/rescript/pull/8520
 - Preserve parentheses around multiplication, division, and modulo expressions used as exponents. https://github.com/rescript-lang/rescript/pull/8550
 - Enforce function arity in interface/module inclusion, type equality, and coercion. https://github.com/rescript-lang/rescript/pull/8559
+- Fix bare labeled arrow types (`~x: int => string`) getting no arity and failing to unify with their parenthesized form. https://github.com/rescript-lang/rescript/pull/8563
 
 # 12.3.0
 
diff --git a/compiler/syntax/src/res_core.ml b/compiler/syntax/src/res_core.ml
index 0d7ef55e960..419a2180ea7 100644
--- a/compiler/syntax/src/res_core.ml
+++ b/compiler/syntax/src/res_core.ml
@@ -4726,7 +4726,7 @@ and parse_es6_arrow_type ~attrs p =
     Parser.expect EqualGreater p;
     let return_type = parse_typ_expr ~alias:false p in
     let loc = mk_loc start_pos p.prev_end_pos in
-    Ast_helper.Typ.arrow ~loc ~arity:None {attrs; lbl; typ} return_type
+    Ast_helper.Typ.arrow ~loc ~arity:(Some 1) {attrs; lbl; typ} return_type
   | DocComment _ -> assert false
   | _ ->
     let parameters = parse_type_parameters p in
diff --git a/tests/syntax_tests/data/parsing/errors/typexpr/expected/arrow.res.txt b/tests/syntax_tests/data/parsing/errors/typexpr/expected/arrow.res.txt
index c621d68f7f0..31e172542b1 100644
--- a/tests/syntax_tests/data/parsing/errors/typexpr/expected/arrow.res.txt
+++ b/tests/syntax_tests/data/parsing/errors/typexpr/expected/arrow.res.txt
@@ -46,5 +46,5 @@ module Error3 =
     type nonrec observation =
       {
       observed: int ;
-      onStep: currentValue:unit -> [%rescript.typehole ] }
+      onStep: currentValue:unit -> [%rescript.typehole ] (a:1) }
   end
\ No newline at end of file
diff --git a/tests/syntax_tests/data/parsing/grammar/typexpr/expected/es6Arrow.res.txt b/tests/syntax_tests/data/parsing/grammar/typexpr/expected/es6Arrow.res.txt
index 47f23df4998..f302e57ce11 100644
--- a/tests/syntax_tests/data/parsing/grammar/typexpr/expected/es6Arrow.res.txt
+++ b/tests/syntax_tests/data/parsing/grammar/typexpr/expected/es6Arrow.res.txt
@@ -12,15 +12,15 @@ let (t : a:int -> b:int -> int (a:2)) = xf
 let (t : ?a:int -> ?b:int -> int (a:2)) = xf
 let (t : int -> int -> int -> int (a:1) (a:1) (a:1)) = xf
 let (t : a:int -> b:int -> c:int -> int (a:1) (a:1) (a:1)) = xf
-type nonrec t = f:int -> string
-type nonrec t = ?f:int -> string
-let (f : f:int -> string) = fx
-let (f : ?f:int -> string) = fx
 type nonrec t = f:int -> string (a:1)
-type nonrec t = f:int -> string
+type nonrec t = ?f:int -> string (a:1)
+let (f : f:int -> string (a:1)) = fx
+let (f : ?f:int -> string (a:1)) = fx
+type nonrec t = f:int -> string (a:1)
+type nonrec t = f:int -> string (a:1)
+type nonrec t = f:(int -> string (a:1)) -> float (a:1)
 type nonrec t = f:(int -> string (a:1)) -> float (a:1)
-type nonrec t = f:(int -> string (a:1)) -> float
-type nonrec t = f:int -> string -> float (a:1)
+type nonrec t = f:int -> string -> float (a:1) (a:1)
 type nonrec t =
   a:int[@attrBeforeLblA ] ->
     b:int[@attrBeforeLblB ] -> ((float)[@attr ]) -> unit (a:3)
@@ -28,7 +28,7 @@ type nonrec t =
   ((a:int ->
       ((b:int -> ((float)[@attr ]) -> unit (a:1) (a:1))[@attrBeforeLblB ]) (a:1))
   [@attrBeforeLblA ])
-type nonrec t = a:int[@attr ] -> unit
+type nonrec t = a:int[@attr ] -> unit (a:1)
 type nonrec 'a getInitialPropsFn =
   < query: string dict  ;req: 'a Js.t Js.Nullable.t   >  ->
     'a Js.t Js.Promise.t (a:1)
\ No newline at end of file

From aba63a00731e86786eab5f2b256f193d22e3f3a3 Mon Sep 17 00:00:00 2001
From: Christoph Knittel <ck@cca.io>
Date: Wed, 19 Aug 2026 12:49:00 +0200
Subject: [PATCH 09/10] Set version to 12.3.1

---
 compiler/common/bs_version.ml                  | 2 +-
 package.json                                   | 2 +-
 packages/@rescript/darwin-arm64/package.json   | 2 +-
 packages/@rescript/darwin-x64/package.json     | 2 +-
 packages/@rescript/linux-arm64/package.json    | 2 +-
 packages/@rescript/linux-x64/package.json      | 2 +-
 packages/@rescript/runtime/package.json        | 2 +-
 packages/@rescript/win32-x64/package.json      | 2 +-
 rewatch/Cargo.lock                             | 2 +-
 rewatch/Cargo.toml                             | 2 +-
 tests/dependencies/rescript-react/package.json | 2 +-
 yarn.config.cjs                                | 2 +-
 12 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/compiler/common/bs_version.ml b/compiler/common/bs_version.ml
index 9a7ea1c30fd..ef3033dbef5 100644
--- a/compiler/common/bs_version.ml
+++ b/compiler/common/bs_version.ml
@@ -21,5 +21,5 @@
  * You should have received a copy of the GNU Lesser General Public License
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. *)
-let version = "12.3.0"
+let version = "12.3.1"
 let header = "// Generated by ReScript, PLEASE EDIT WITH CARE"
diff --git a/package.json b/package.json
index 84d4ac69d9f..1148b49edb4 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "rescript",
-  "version": "12.3.0",
+  "version": "12.3.1",
   "description": "ReScript toolchain",
   "type": "module",
   "keywords": [
diff --git a/packages/@rescript/darwin-arm64/package.json b/packages/@rescript/darwin-arm64/package.json
index f76e3b499c0..b649eb29348 100644
--- a/packages/@rescript/darwin-arm64/package.json
+++ b/packages/@rescript/darwin-arm64/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@rescript/darwin-arm64",
-  "version": "12.3.0",
+  "version": "12.3.1",
   "description": "ReScript binaries for MacOS ARM64",
   "type": "module",
   "license": "(LGPL-3.0-or-later AND MIT)",
diff --git a/packages/@rescript/darwin-x64/package.json b/packages/@rescript/darwin-x64/package.json
index 34848583cb3..7a1187151fd 100644
--- a/packages/@rescript/darwin-x64/package.json
+++ b/packages/@rescript/darwin-x64/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@rescript/darwin-x64",
-  "version": "12.3.0",
+  "version": "12.3.1",
   "description": "ReScript binaries for MacOS x86_64",
   "type": "module",
   "license": "(LGPL-3.0-or-later AND MIT)",
diff --git a/packages/@rescript/linux-arm64/package.json b/packages/@rescript/linux-arm64/package.json
index 3486e6144f1..e2bae4c28f0 100644
--- a/packages/@rescript/linux-arm64/package.json
+++ b/packages/@rescript/linux-arm64/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@rescript/linux-arm64",
-  "version": "12.3.0",
+  "version": "12.3.1",
   "description": "ReScript binaries for Linux ARM64",
   "type": "module",
   "license": "(LGPL-3.0-or-later AND MIT)",
diff --git a/packages/@rescript/linux-x64/package.json b/packages/@rescript/linux-x64/package.json
index efcbcdb344a..8b336059459 100644
--- a/packages/@rescript/linux-x64/package.json
+++ b/packages/@rescript/linux-x64/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@rescript/linux-x64",
-  "version": "12.3.0",
+  "version": "12.3.1",
   "description": "ReScript binaries for Linux x86_64",
   "type": "module",
   "license": "(LGPL-3.0-or-later AND MIT)",
diff --git a/packages/@rescript/runtime/package.json b/packages/@rescript/runtime/package.json
index 6020ea0d00d..d2a74bfcf22 100644
--- a/packages/@rescript/runtime/package.json
+++ b/packages/@rescript/runtime/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@rescript/runtime",
-  "version": "12.3.0",
+  "version": "12.3.1",
   "description": "ReScript runtime modules",
   "type": "module",
   "license": "MIT",
diff --git a/packages/@rescript/win32-x64/package.json b/packages/@rescript/win32-x64/package.json
index 8a9857c672e..f7fa1c09414 100644
--- a/packages/@rescript/win32-x64/package.json
+++ b/packages/@rescript/win32-x64/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@rescript/win32-x64",
-  "version": "12.3.0",
+  "version": "12.3.1",
   "description": "ReScript binaries for Windows x86_64",
   "type": "module",
   "license": "(LGPL-3.0-or-later AND MIT)",
diff --git a/rewatch/Cargo.lock b/rewatch/Cargo.lock
index 1397372d1c5..a81293a385d 100644
--- a/rewatch/Cargo.lock
+++ b/rewatch/Cargo.lock
@@ -768,7 +768,7 @@ checksum = "2b15c43186be67a4fd63bee50d0303afffcef381492ebe2c5d87f324e1b8815c"
 
 [[package]]
 name = "rescript"
-version = "12.3.0"
+version = "12.3.1"
 dependencies = [
  "ahash",
  "anyhow",
diff --git a/rewatch/Cargo.toml b/rewatch/Cargo.toml
index 35576d57196..c05014cb728 100644
--- a/rewatch/Cargo.toml
+++ b/rewatch/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "rescript"
-version = "12.3.0"
+version = "12.3.1"
 edition = "2024"
 rust-version = "1.91"
 
diff --git a/tests/dependencies/rescript-react/package.json b/tests/dependencies/rescript-react/package.json
index 6271f397f34..8a863b8ad51 100644
--- a/tests/dependencies/rescript-react/package.json
+++ b/tests/dependencies/rescript-react/package.json
@@ -1,7 +1,7 @@
 {
   "name": "@rescript/react",
   "private": true,
-  "version": "12.3.0",
+  "version": "12.3.1",
   "homepage": "https://rescript-lang.org",
   "bugs": "https://github.com/rescript-lang/rescript/issues",
   "repository": {
diff --git a/yarn.config.cjs b/yarn.config.cjs
index d0a45b60606..631382a105f 100644
--- a/yarn.config.cjs
+++ b/yarn.config.cjs
@@ -14,7 +14,7 @@ const execPromise = util.promisify(exec);
  * @param {Yarn.Constraints.Context} ctx
  */
 async function enforceCompilerMeta({ Yarn }) {
-  const EXPECTED_VERSION = "12.3.0";
+  const EXPECTED_VERSION = "12.3.1";
 
   for (const workspace of Yarn.workspaces()) {
     const { ident } = workspace.pkg;

From a1ad1df6e3f5d070410661bb647b56e32109b57c Mon Sep 17 00:00:00 2001
From: Christoph Knittel <ck@cca.io>
Date: Wed, 19 Aug 2026 13:05:37 +0200
Subject: [PATCH 10/10] Move Rewatch test module after production items

---
 rewatch/src/build/compile.rs | 26 +++++++++++++-------------
 1 file changed, 13 insertions(+), 13 deletions(-)

diff --git a/rewatch/src/build/compile.rs b/rewatch/src/build/compile.rs
index 2aa4c264a15..6052d0c0dbf 100644
--- a/rewatch/src/build/compile.rs
+++ b/rewatch/src/build/compile.rs
@@ -966,19 +966,6 @@ pub fn mark_modules_with_deleted_deps_dirty(build_state: &mut BuildState) {
     });
 }
 
-#[cfg(test)]
-mod tests {
-    use super::compiler_output_to_string;
-
-    #[test]
-    fn compiler_output_to_string_handles_invalid_utf8() {
-        // Start of an em dash (U+2014), with its third byte missing.
-        let truncated = [b'W', b'a', b'r', b'n', b'i', b'n', b'g', b' ', 0xe2, 0x80];
-        let decoded = compiler_output_to_string(&truncated);
-        assert!(decoded.starts_with("Warning "));
-    }
-}
-
 // this happens when a compile is not completed successfully in some way
 // a dependent module could be compiled with a new interface, but the dependent
 // modules have not finished compiling. This can cause a stale build.
@@ -1067,3 +1054,16 @@ pub fn mark_modules_with_expired_deps_dirty(build_state: &mut BuildCommandState)
         }
     });
 }
+
+#[cfg(test)]
+mod tests {
+    use super::compiler_output_to_string;
+
+    #[test]
+    fn compiler_output_to_string_handles_invalid_utf8() {
+        // Start of an em dash (U+2014), with its third byte missing.
+        let truncated = [b'W', b'a', b'r', b'n', b'i', b'n', b'g', b' ', 0xe2, 0x80];
+        let decoded = compiler_output_to_string(&truncated);
+        assert!(decoded.starts_with("Warning "));
+    }
+}