From b524bd455f672f9d709a7374d17ce137370df250 Mon Sep 17 00:00:00 2001
From: Kamil Listopad <listopadkamil@gmail.com>
Date: Mon, 15 Sep 2025 10:53:46 +0200
Subject: [PATCH 01/22] rename artifacts on draft release

---
 .github/workflows/release.yml | 145 ++++++++++++++++++++++------------
 1 file changed, 94 insertions(+), 51 deletions(-)

diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index ad56b69f5cf..71f232058e8 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -3,7 +3,7 @@ name: release
 on:
   push:
     tags:
-    - '*'
+      - "*"
   workflow_dispatch:
     # To test this workflow: Go to Actions -> release -> Run workflow
     # Or using the CLI: gh workflow run release --ref <branch> -f version=test-draft-release
@@ -11,7 +11,7 @@ on:
     # Remember to delete the draft release after testing!
     inputs:
       version:
-        description: 'Version for draft release (default: test-draft-release)'
+        description: "Version for draft release (default: test-draft-release)"
         required: false
         default: test-draft-release
         type: string
@@ -25,19 +25,34 @@ jobs:
       - name: Prepare release
         run: echo "Preparing release for version ${{ inputs.version || github.ref_name }}"
 
+      - name: Validate draft suffix (workflow_dispatch only)
+        if: ${{ github.event_name == 'workflow_dispatch' }}
+        run: |
+          set -eu
+          SUFFIX="${{ inputs.version }}"
+          if [ -z "${SUFFIX:-}" ]; then
+            echo "Error: inputs.version (draft suffix) is empty"
+            exit 1
+          fi
+          # Allow only letters and hyphens
+          if ! printf '%s' "${SUFFIX}" | grep -Eq '^[A-Za-z-]+$'; then
+            echo "Error: inputs.version must contain only letters and hyphens (e.g., experimental-stable-functions)"
+            exit 1
+          fi
+
   # Check that the changelog is in good order and extract the changelog.
   changelog:
     runs-on: ubuntu-latest
     needs: prepare
     steps:
-    - uses: actions/checkout@v5
-    - name: Extract changelog
-      # Skip this step for draft releases. Leave the release body empty.
-      if: ${{ github.event_name != 'workflow_dispatch' }}
-      id: read_changelog
-      uses: ./.github/actions/extract-changelog
-      with:
-        version: ${{ needs.prepare.outputs.version }}
+      - uses: actions/checkout@v5
+      - name: Extract changelog
+        # Skip this step for draft releases. Leave the release body empty.
+        if: ${{ github.event_name != 'workflow_dispatch' }}
+        id: read_changelog
+        uses: ./.github/actions/extract-changelog
+        with:
+          version: ${{ needs.prepare.outputs.version }}
     outputs:
       release_body: ${{ steps.read_changelog.outputs.release_body }}
 
@@ -45,59 +60,87 @@ jobs:
     needs: prepare
     strategy:
       matrix:
-        os: [ ubuntu-latest, macos-13, ubuntu-24.04-arm, macos-latest ]
+        os: [ubuntu-latest, macos-13, ubuntu-24.04-arm, macos-latest]
     concurrency:
       group: release-build-${{ matrix.os }}-${{ needs.prepare.outputs.version }}
       cancel-in-progress: true
     runs-on: ${{ matrix.os }}
     steps:
-    - uses: actions/checkout@v5
-    - uses: cachix/install-nix-action@v31
-    - uses: cachix/cachix-action@v16
-      with:
-        name: ic-hs-test
-        # NB: No auth token, we don't expect to push new stuff here
+      - uses: actions/checkout@v5
+      - uses: cachix/install-nix-action@v31
+      - uses: cachix/cachix-action@v16
+        with:
+          name: ic-hs-test
+          # NB: No auth token, we don't expect to push new stuff here
 
-    - name: Build platform-specific release files
-      run: nix build --max-jobs 1 '.#"release-files-${{ matrix.os }}"'
+      - name: Build platform-specific release files
+        run: nix build --max-jobs 1 '.#"release-files-${{ matrix.os }}"'
 
-    - name: Upload Release Artifacts
-      uses: actions/upload-artifact@v4
-      with:
-        name: release-files-${{ matrix.os }}
-        path: result/*
+      - name: Upload Release Artifacts
+        uses: actions/upload-artifact@v4
+        with:
+          name: release-files-${{ matrix.os }}
+          path: result/*
 
-    - name: Test release files
-      run: |
-        uname -s -m
-        moc="$(nix build --max-jobs 1 .#release.moc --print-out-paths)"
-        "$moc/bin/moc" --version
-        file "$moc/bin/moc"
-        ldd "$moc/bin/moc" || true
+      - name: Test release files
+        run: |
+          uname -s -m
+          moc="$(nix build --max-jobs 1 .#release.moc --print-out-paths)"
+          "$moc/bin/moc" --version
+          file "$moc/bin/moc"
+          ldd "$moc/bin/moc" || true
 
   publish:
     runs-on: ubuntu-latest
     needs: [prepare, changelog, build]
     steps:
-    - name: Download all release artifacts
-      uses: actions/download-artifact@v5
-      with:
-        path: release-assets
-        pattern: release-files-*
-        merge-multiple: true
+      - name: Download all release artifacts
+        uses: actions/download-artifact@v5
+        with:
+          path: release-assets
+          pattern: release-files-*
+          merge-multiple: true
+
+      - name: Rewrite artifact filenames with draft suffix
+        if: ${{ github.event_name == 'workflow_dispatch' }}
+        env:
+          DRAFT_SUFFIX: ${{ inputs.version }}
+        run: |
+          set -eu
+          echo "Applying draft suffix: ${DRAFT_SUFFIX}"
+          dir="release-assets"
+          # Extract numeric version from moc-<version>.js
+          version="$(ls "$dir"/moc-*.js 2>/dev/null | sed -n 's#.*moc-\([0-9.]\+\)\.js#\1#p' | head -n1 || true)"
+          if [ -z "${version}" ]; then
+            echo "Could not determine base version from moc-*.js; skipping rename."
+            exit 0
+          fi
+          echo "Detected base version: ${version}"
+          # Rename JS artifacts
+          if [ -f "$dir/moc-${version}.js" ]; then
+            mv "$dir/moc-${version}.js" "$dir/moc-${version}-${DRAFT_SUFFIX}.js"
+          fi
+          if [ -f "$dir/moc-interpreter-${version}.js" ]; then
+            mv "$dir/moc-interpreter-${version}.js" "$dir/moc-interpreter-${version}-${DRAFT_SUFFIX}.js"
+          fi
+          # Rename tarballs
+          for f in "$dir"/*-"${version}".tar.gz; do
+            [ -e "$f" ] || continue
+            mv "$f" "${f%.tar.gz}-${DRAFT_SUFFIX}.tar.gz"
+          done
 
-    - name: List downloaded files
-      run: |
-        echo "Contents of release-assets directory:"
-        find release-assets -type f -ls || true
+      - name: List downloaded files
+        run: |
+          echo "Contents of release-assets directory:"
+          find release-assets -type f -ls || true
 
-    - name: Upload Release Assets
-      uses: svenstaro/upload-release-action@v2
-      with:
-        repo_token: ${{ secrets.GITHUB_TOKEN }}
-        tag: ${{ needs.prepare.outputs.version }}
-        file: release-assets/*
-        file_glob: true
-        body: ${{ needs.changelog.outputs.release_body || 'Draft release created for testing purposes' }}
-        draft: ${{ github.event_name == 'workflow_dispatch' }}
-        prerelease: ${{ github.event_name == 'workflow_dispatch' }}
+      - name: Upload Release Assets
+        uses: svenstaro/upload-release-action@v2
+        with:
+          repo_token: ${{ secrets.GITHUB_TOKEN }}
+          tag: ${{ needs.prepare.outputs.version }}
+          file: release-assets/*
+          file_glob: true
+          body: ${{ needs.changelog.outputs.release_body || 'Draft release created for testing purposes' }}
+          draft: ${{ github.event_name == 'workflow_dispatch' }}
+          prerelease: ${{ github.event_name == 'workflow_dispatch' }}

From f65a429597ab4d336c8f2f8c4eb40e8c43777252 Mon Sep 17 00:00:00 2001
From: Kamil Listopad <listopadkamil@gmail.com>
Date: Mon, 15 Sep 2025 10:59:38 +0200
Subject: [PATCH 02/22] try to link motoko-core to luc/oo-data-structures

---
 flake.lock | 7 ++++---
 flake.nix  | 2 +-
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/flake.lock b/flake.lock
index d39bb2b6898..c6b156a6d51 100644
--- a/flake.lock
+++ b/flake.lock
@@ -137,15 +137,16 @@
     "motoko-core-src": {
       "flake": false,
       "locked": {
-        "lastModified": 1756913868,
-        "narHash": "sha256-zLJShje+X/+4yM0wTwNB9Bri00SH6G3vOvyUP56KdwU=",
+        "lastModified": 1757337895,
+        "narHash": "sha256-G5BlQfm/TJ0Trk5owOGDOTxoigcf5ErgnSEDyPe20fk=",
         "owner": "dfinity",
         "repo": "motoko-core",
-        "rev": "e397d7e577491703d94a1f82dc88ff01c59c0dbd",
+        "rev": "59310bfed843c072882ad48980a366fb87f19f03",
         "type": "github"
       },
       "original": {
         "owner": "dfinity",
+        "ref": "luc/oo-data-structures",
         "repo": "motoko-core",
         "type": "github"
       }
diff --git a/flake.nix b/flake.nix
index 0489f9d7e63..67843862985 100644
--- a/flake.nix
+++ b/flake.nix
@@ -46,7 +46,7 @@
       flake = false;
     };
     motoko-core-src = {
-      url = "github:dfinity/motoko-core";
+      url = "github:dfinity/motoko-core/luc/oo-data-structures";
       flake = false;
     };
     motoko-matchers-src = {

From cc4fab23814bd8857821ed84305a1b3433ae9c11 Mon Sep 17 00:00:00 2001
From: Kamil Listopad <listopadkamil@gmail.com>
Date: Mon, 15 Sep 2025 11:35:22 +0200
Subject: [PATCH 03/22] allow digits

---
 .github/workflows/release.yml | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index 71f232058e8..ddbd8ed0d53 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -34,9 +34,9 @@ jobs:
             echo "Error: inputs.version (draft suffix) is empty"
             exit 1
           fi
-          # Allow only letters and hyphens
-          if ! printf '%s' "${SUFFIX}" | grep -Eq '^[A-Za-z-]+$'; then
-            echo "Error: inputs.version must contain only letters and hyphens (e.g., experimental-stable-functions)"
+          # Allow only letters, digits, and hyphens
+          if ! printf '%s' "${SUFFIX}" | grep -Eq '^[A-Za-z0-9-]+$'; then
+            echo "Error: inputs.version must contain only letters, digits, and hyphens (e.g., experimental-foo-2)"
             exit 1
           fi
 

From 2a5e94e10f45c92ad5f40ddaa10c0259fa48be15 Mon Sep 17 00:00:00 2001
From: Kamil Listopad <listopadkamil@gmail.com>
Date: Mon, 15 Sep 2025 12:47:17 +0200
Subject: [PATCH 04/22] repro type inference needs fixing

---
 test/run/use-persistent-function.mo | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)
 create mode 100644 test/run/use-persistent-function.mo

diff --git a/test/run/use-persistent-function.mo b/test/run/use-persistent-function.mo
new file mode 100644
index 00000000000..f561345cb63
--- /dev/null
+++ b/test/run/use-persistent-function.mo
@@ -0,0 +1,25 @@
+import Prim "mo:⛔";
+
+type Order = { #less; #equal; #greater };
+
+module Array {
+  public func sort<T>(array : [T], compare : (T, T) -> Order) : [T] {
+    if (compare(array[0], array[1]) == #less) {
+      [array[0], array[1]];
+    } else {
+      array;
+    };
+  };
+};
+
+module Nat {
+  public persistent func compare(x : Nat, y : Nat) : Order {
+    if (x < y) { #less } else if (x == y) { #equal } else { #greater };
+  };
+};
+
+let a : [Nat] = [2, 1];
+let b : [Nat] = [1, 2];
+
+assert Array.sort(a, Nat.compare) == [1, 2];
+assert Array.sort(b, Nat.compare) == [1, 2];

From 9ccfb8caf191d1e32f1a2da1c3f9be0e2e583ac4 Mon Sep 17 00:00:00 2001
From: Kamil Listopad <listopadkamil@gmail.com>
Date: Mon, 15 Sep 2025 14:00:56 +0200
Subject: [PATCH 05/22] bug?

---
 test/run/use-persistent-function.mo | 2 --
 1 file changed, 2 deletions(-)

diff --git a/test/run/use-persistent-function.mo b/test/run/use-persistent-function.mo
index f561345cb63..5e5d9634517 100644
--- a/test/run/use-persistent-function.mo
+++ b/test/run/use-persistent-function.mo
@@ -1,5 +1,3 @@
-import Prim "mo:⛔";
-
 type Order = { #less; #equal; #greater };
 
 module Array {

From e016f2fe53c226757d41c9c5eab77b5336dec63e Mon Sep 17 00:00:00 2001
From: Kamil Listopad <listopadkamil@gmail.com>
Date: Mon, 15 Sep 2025 14:22:29 +0200
Subject: [PATCH 06/22] claudio bimatch repro

---
 test/run-drun/bimatch-persistent-func.mo | 7 +++++++
 1 file changed, 7 insertions(+)
 create mode 100644 test/run-drun/bimatch-persistent-func.mo

diff --git a/test/run-drun/bimatch-persistent-func.mo b/test/run-drun/bimatch-persistent-func.mo
new file mode 100644
index 00000000000..4e8648ac800
--- /dev/null
+++ b/test/run-drun/bimatch-persistent-func.mo
@@ -0,0 +1,7 @@
+persistent actor {
+   persistent func g<T>(x : T) : persistent () -> T {
+     persistent func h() : T { x };
+     h;
+   };
+   stable let h = g<persistent () -> ()>(func () {});
+}
\ No newline at end of file

From 1447d0f0214ca42778c6a08d76f4b4087970d1c5 Mon Sep 17 00:00:00 2001
From: Kamil Listopad <listopadkamil@gmail.com>
Date: Mon, 15 Sep 2025 20:39:00 +0200
Subject: [PATCH 07/22] missing error where assert was

---
 src/mo_frontend/typing.ml                          |  3 ++-
 test/run-drun/bimatch-persistent-func.mo           | 12 ++++++------
 test/run-drun/ok/bimatch-persistent-func.tc.ok     |  5 +++++
 test/run-drun/ok/bimatch-persistent-func.tc.ret.ok |  1 +
 4 files changed, 14 insertions(+), 7 deletions(-)
 create mode 100644 test/run-drun/ok/bimatch-persistent-func.tc.ok
 create mode 100644 test/run-drun/ok/bimatch-persistent-func.tc.ret.ok

diff --git a/src/mo_frontend/typing.ml b/src/mo_frontend/typing.ml
index cb577c71f35..333a3dafc62 100644
--- a/src/mo_frontend/typing.ml
+++ b/src/mo_frontend/typing.ml
@@ -2308,7 +2308,8 @@ and check_func_step in_actor env (shared_pat, pat, typ_opt, exp) (s, c, ts1, ts2
   if sort <> s then
     (match sort, s with
       | T.Local T.Stable, T.Local T.Flexible -> () (* okay *)
-      | T.Local _, T.Local _ -> assert false (* caught by sub-type check *)
+      | T.Local _, T.Local _ ->
+        error env exp.at "M0220" "this function should be declared `persistent`"
       | _, _ ->
         error env exp.at "M0094"
           "%sshared function does not match expected %sshared function type"
diff --git a/test/run-drun/bimatch-persistent-func.mo b/test/run-drun/bimatch-persistent-func.mo
index 4e8648ac800..feba3833f99 100644
--- a/test/run-drun/bimatch-persistent-func.mo
+++ b/test/run-drun/bimatch-persistent-func.mo
@@ -1,7 +1,7 @@
 persistent actor {
-   persistent func g<T>(x : T) : persistent () -> T {
-     persistent func h() : T { x };
-     h;
-   };
-   stable let h = g<persistent () -> ()>(func () {});
-}
\ No newline at end of file
+  persistent func g<T>(x : T) : persistent() -> T {
+    persistent func h() : T { x };
+    h;
+  };
+  stable let h = g<persistent() -> ()>(func() {});
+};
diff --git a/test/run-drun/ok/bimatch-persistent-func.tc.ok b/test/run-drun/ok/bimatch-persistent-func.tc.ok
new file mode 100644
index 00000000000..7c09f182921
--- /dev/null
+++ b/test/run-drun/ok/bimatch-persistent-func.tc.ok
@@ -0,0 +1,5 @@
+bimatch-persistent-func.mo:4.5-4.6: type error [M0096], expression of type
+  () -> T
+cannot produce expected type
+  persistent () -> T
+bimatch-persistent-func.mo:6.47-6.49: type error [M0220], this function should be declared `persistent`
diff --git a/test/run-drun/ok/bimatch-persistent-func.tc.ret.ok b/test/run-drun/ok/bimatch-persistent-func.tc.ret.ok
new file mode 100644
index 00000000000..69becfa16f9
--- /dev/null
+++ b/test/run-drun/ok/bimatch-persistent-func.tc.ret.ok
@@ -0,0 +1 @@
+Return code 1

From b309b935ff2e79087fb3f799ae763420c56e57a8 Mon Sep 17 00:00:00 2001
From: Kamil Listopad <listopadkamil@gmail.com>
Date: Tue, 16 Sep 2025 10:34:58 +0200
Subject: [PATCH 08/22] claudio test with module in test/fail

---
 .../ok/persistent-func-type-argument-and-return.tc.ok     | 1 +
 .../ok/persistent-func-type-argument-and-return.tc.ret.ok | 1 +
 test/fail/persistent-func-type-argument-and-return.mo     | 8 ++++++++
 3 files changed, 10 insertions(+)
 create mode 100644 test/fail/ok/persistent-func-type-argument-and-return.tc.ok
 create mode 100644 test/fail/ok/persistent-func-type-argument-and-return.tc.ret.ok
 create mode 100644 test/fail/persistent-func-type-argument-and-return.mo

diff --git a/test/fail/ok/persistent-func-type-argument-and-return.tc.ok b/test/fail/ok/persistent-func-type-argument-and-return.tc.ok
new file mode 100644
index 00000000000..81d632c9bc0
--- /dev/null
+++ b/test/fail/ok/persistent-func-type-argument-and-return.tc.ok
@@ -0,0 +1 @@
+persistent-func-type-argument-and-return.mo:6.40-6.42: type error [M0220], this function should be declared `persistent`
diff --git a/test/fail/ok/persistent-func-type-argument-and-return.tc.ret.ok b/test/fail/ok/persistent-func-type-argument-and-return.tc.ret.ok
new file mode 100644
index 00000000000..69becfa16f9
--- /dev/null
+++ b/test/fail/ok/persistent-func-type-argument-and-return.tc.ret.ok
@@ -0,0 +1 @@
+Return code 1
diff --git a/test/fail/persistent-func-type-argument-and-return.mo b/test/fail/persistent-func-type-argument-and-return.mo
new file mode 100644
index 00000000000..e0038ac4edd
--- /dev/null
+++ b/test/fail/persistent-func-type-argument-and-return.mo
@@ -0,0 +1,8 @@
+module {
+  persistent func g<T>(x : T) : persistent() -> T {
+    persistent func h() : T { x };
+    h; // TODO: non-eop should still typecheck here
+  };
+  // don't allow `func() {}` to typecheck as `persistent() -> ()` for now
+  let h = g<persistent() -> ()>(func() {});
+};

From ad5b9d1efb5c5688ba046aee77544f129f818268 Mon Sep 17 00:00:00 2001
From: Kamil Listopad <listopadkamil@gmail.com>
Date: Tue, 16 Sep 2025 10:41:48 +0200
Subject: [PATCH 09/22] eop only test, running

---
 test/run-drun/ok/bimatch-persistent-func.tc.ok               | 5 -----
 test/run-drun/ok/bimatch-persistent-func.tc.ret.ok           | 1 -
 ...with-persistent-funcs-in-type-args-and-return.drun-run.ok | 2 ++
 ...t-actor-with-persistent-funcs-in-type-args-and-return.mo} | 4 +++-
 4 files changed, 5 insertions(+), 7 deletions(-)
 delete mode 100644 test/run-drun/ok/bimatch-persistent-func.tc.ok
 delete mode 100644 test/run-drun/ok/bimatch-persistent-func.tc.ret.ok
 create mode 100644 test/run-drun/ok/persistent-actor-with-persistent-funcs-in-type-args-and-return.drun-run.ok
 rename test/run-drun/{bimatch-persistent-func.mo => persistent-actor-with-persistent-funcs-in-type-args-and-return.mo} (53%)

diff --git a/test/run-drun/ok/bimatch-persistent-func.tc.ok b/test/run-drun/ok/bimatch-persistent-func.tc.ok
deleted file mode 100644
index 7c09f182921..00000000000
--- a/test/run-drun/ok/bimatch-persistent-func.tc.ok
+++ /dev/null
@@ -1,5 +0,0 @@
-bimatch-persistent-func.mo:4.5-4.6: type error [M0096], expression of type
-  () -> T
-cannot produce expected type
-  persistent () -> T
-bimatch-persistent-func.mo:6.47-6.49: type error [M0220], this function should be declared `persistent`
diff --git a/test/run-drun/ok/bimatch-persistent-func.tc.ret.ok b/test/run-drun/ok/bimatch-persistent-func.tc.ret.ok
deleted file mode 100644
index 69becfa16f9..00000000000
--- a/test/run-drun/ok/bimatch-persistent-func.tc.ret.ok
+++ /dev/null
@@ -1 +0,0 @@
-Return code 1
diff --git a/test/run-drun/ok/persistent-actor-with-persistent-funcs-in-type-args-and-return.drun-run.ok b/test/run-drun/ok/persistent-actor-with-persistent-funcs-in-type-args-and-return.drun-run.ok
new file mode 100644
index 00000000000..a6f776f43c6
--- /dev/null
+++ b/test/run-drun/ok/persistent-actor-with-persistent-funcs-in-type-args-and-return.drun-run.ok
@@ -0,0 +1,2 @@
+ingress Completed: Reply: 0x4449444c016c01b3c4b1f204680100010a00000000000000000101
+ingress Completed: Reply: 0x4449444c0000
diff --git a/test/run-drun/bimatch-persistent-func.mo b/test/run-drun/persistent-actor-with-persistent-funcs-in-type-args-and-return.mo
similarity index 53%
rename from test/run-drun/bimatch-persistent-func.mo
rename to test/run-drun/persistent-actor-with-persistent-funcs-in-type-args-and-return.mo
index feba3833f99..64f2f986dd4 100644
--- a/test/run-drun/bimatch-persistent-func.mo
+++ b/test/run-drun/persistent-actor-with-persistent-funcs-in-type-args-and-return.mo
@@ -1,7 +1,9 @@
+//ENHANCED-ORTHOGONAL-PERSISTENCE-ONLY
 persistent actor {
   persistent func g<T>(x : T) : persistent() -> T {
     persistent func h() : T { x };
     h;
   };
-  stable let h = g<persistent() -> ()>(func() {});
+  let h = g<persistent() -> ()>(persistent func _anon() {});
+  h();
 };

From 4600bd3f34ddbfc2e8c49dcabf03f6e1eaf016df Mon Sep 17 00:00:00 2001
From: Kamil Listopad <listopadkamil@gmail.com>
Date: Tue, 16 Sep 2025 10:42:38 +0200
Subject: [PATCH 10/22] rel_sort, combine_sort

---
 src/mo_frontend/bi_match.ml |  2 +-
 src/mo_types/type.ml        | 17 +++++++++++++++--
 src/mo_types/type.mli       |  1 +
 3 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/src/mo_frontend/bi_match.ml b/src/mo_frontend/bi_match.ml
index 8fdaa24dcf4..60f2bc6a0a4 100644
--- a/src/mo_frontend/bi_match.ml
+++ b/src/mo_frontend/bi_match.ml
@@ -261,7 +261,7 @@ let bi_match_typs ctx =
     | Tup ts1, Tup ts2 ->
       bi_match_list bi_match_typ rel eq inst any ts1 ts2
     | Func (s1, c1, tbs1, t11, t12), Func (s2, c2, tbs2, t21, t22) ->
-      if s1 = s2 && c1 = c2 then
+      if rel_sort s1 s2 tbs1 && c1 = c2 then
       (match bi_match_binds rel eq inst any tbs1 tbs2 with
        | Some (inst, ts) ->
          let any' = List.fold_right
diff --git a/src/mo_types/type.ml b/src/mo_types/type.ml
index c749175a558..1c691ab50d2 100644
--- a/src/mo_types/type.ml
+++ b/src/mo_types/type.ml
@@ -1593,15 +1593,17 @@ let rec combine rel lubs glbs t1 t2 =
       (try Obj (s1, combine_fields rel lubs glbs tf1 tf2)
       with Mismatch -> assert (rel == glbs); Non)
     | Func (s1, c1, bs1, ts11, ts12), Func (s2, c2, bs2, ts21, ts22) when
-        s1 = s2 && c1 = c2 && eq_binds bs1 bs2 &&
+        combine_sort rel lubs glbs s1 s2 bs1 bs2 <> None &&
+        c1 = c2 && eq_binds bs1 bs2 &&
         List.(length ts11 = length ts21 && length ts12 = length ts22) ->
       let ts = open_binds bs1 in
       let cs = List.map (fun t -> fst (as_con t)) ts in
       let opened = List.map (open_ ts) in
       let closed = List.map (close cs) in
       let rel' = if rel == lubs then glbs else lubs in
+      let s = Option.get (combine_sort rel lubs glbs s1 s2 bs1 bs2) in
       Func (
-        s1, c1, bs1,
+        s, c1, bs1,
         closed (List.map2 (combine rel' lubs glbs) (opened ts11) (opened ts21)),
         closed (List.map2 (combine rel lubs glbs) (opened ts12) (opened ts22))
       )
@@ -1647,6 +1649,17 @@ let rec combine rel lubs glbs t1 t2 =
     | _, _ ->
       if rel == lubs then Any else Non
 
+and combine_sort rel lubs glbs s1 s2 bs1 bs2=
+  if s1 = s2 then Some s1 else
+  let both s = 
+    if rel_sort s1 s bs1 && rel_sort s2 s bs2 then Some s
+   else None
+  in
+  if rel == lubs then
+    both (Local Flexible)
+  else
+    both (Local Stable)
+
 and cons_if b x xs = if b then x::xs else xs
 
 and combine_fields rel lubs glbs fs1 fs2 =
diff --git a/src/mo_types/type.mli b/src/mo_types/type.mli
index 4d7e950dfac..ca420945b4b 100644
--- a/src/mo_types/type.mli
+++ b/src/mo_types/type.mli
@@ -276,6 +276,7 @@ val eq_kind : ?src_fields : Field_sources.t -> kind -> kind -> bool
 val sub : ?src_fields : Field_sources.t -> typ -> typ -> bool
 val sub_explained : ?src_fields : Field_sources.t -> context -> typ -> typ -> compatibility
 val compatible : typ -> typ -> bool
+val rel_sort : func_sort -> func_sort -> bind list -> bool
 
 exception PreEncountered
 val lub : ?src_fields : Field_sources.t -> typ -> typ -> typ

From f3cd87204cae8a3c476d718fe15b187b8e011e8b Mon Sep 17 00:00:00 2001
From: Kamil Listopad <listopadkamil@gmail.com>
Date: Tue, 16 Sep 2025 11:10:12 +0200
Subject: [PATCH 11/22] fix test

---
 test/run/use-persistent-function.mo | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/test/run/use-persistent-function.mo b/test/run/use-persistent-function.mo
index 5e5d9634517..0373b00de05 100644
--- a/test/run/use-persistent-function.mo
+++ b/test/run/use-persistent-function.mo
@@ -2,8 +2,8 @@ type Order = { #less; #equal; #greater };
 
 module Array {
   public func sort<T>(array : [T], compare : (T, T) -> Order) : [T] {
-    if (compare(array[0], array[1]) == #less) {
-      [array[0], array[1]];
+    if (compare(array[0], array[1]) == #greater) {
+      [array[1], array[0]];
     } else {
       array;
     };

From 66b6b957123514a8fcb0d9a2e48a2fd470129f29 Mon Sep 17 00:00:00 2001
From: Kamil Listopad <listopadkamil@gmail.com>
Date: Tue, 16 Sep 2025 11:27:05 +0200
Subject: [PATCH 12/22] line change

---
 test/fail/ok/persistent-func-type-argument-and-return.tc.ok | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/test/fail/ok/persistent-func-type-argument-and-return.tc.ok b/test/fail/ok/persistent-func-type-argument-and-return.tc.ok
index 81d632c9bc0..f1a932f5c7b 100644
--- a/test/fail/ok/persistent-func-type-argument-and-return.tc.ok
+++ b/test/fail/ok/persistent-func-type-argument-and-return.tc.ok
@@ -1 +1 @@
-persistent-func-type-argument-and-return.mo:6.40-6.42: type error [M0220], this function should be declared `persistent`
+persistent-func-type-argument-and-return.mo:7.40-7.42: type error [M0220], this function should be declared `persistent`

From 2832156aab779b06790d1839abb3c7334e86b3d3 Mon Sep 17 00:00:00 2001
From: Kamil Listopad <listopadkamil@gmail.com>
Date: Tue, 16 Sep 2025 11:27:53 +0200
Subject: [PATCH 13/22] try disabling implicit func conversion from Stable to
 Flexible when eop flag is off

---
 src/mo_frontend/typing.ml | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/mo_frontend/typing.ml b/src/mo_frontend/typing.ml
index 333a3dafc62..1665656fe73 100644
--- a/src/mo_frontend/typing.ml
+++ b/src/mo_frontend/typing.ml
@@ -1697,10 +1697,10 @@ and infer_exp'' env exp : T.typ =
     | _ -> ()
     end;
     let sort, ve = check_shared_pat env shared_pat in
-    let sort = match sort, !Mo_config.Flags.enhanced_orthogonal_persistence with
+    (* let sort = match sort, !Mo_config.Flags.enhanced_orthogonal_persistence with
     | T.Local T.Stable, false -> T.Local T.Flexible (* named local functions are flexible in classical mode *)
     | _ -> sort
-    in
+    in *)
     let is_async = match typ_opt with
       | Some { it = AsyncT _; _ } -> true
       | _ -> false
@@ -1769,7 +1769,7 @@ and infer_exp'' env exp : T.typ =
       end
     end;
     let ts1 = match pat.it with TupP _ -> T.seq_of_tup t1 | _ -> [t1] in
-    let sort = if is_flexible && sort = T.Local T.Stable then T.Local T.Flexible else sort in
+    (* let sort = if is_flexible && sort = T.Local T.Stable then T.Local T.Flexible else sort in *)
     T.Func (sort, c, T.close_binds cs tbs, List.map (T.close cs) ts1, List.map (T.close cs) ts2)
   | CallE (par_opt, exp1, inst, exp2) ->
     let t = infer_call env exp1 inst exp2 exp.at None in

From 64789bc17338dc4c14d45b26b2fc1e19495907fb Mon Sep 17 00:00:00 2001
From: Kamil Listopad <listopadkamil@gmail.com>
Date: Tue, 16 Sep 2025 12:43:56 +0200
Subject: [PATCH 14/22] script for replacing mops-cached moc, with backups and
 restore

---
 scripts/replace-mops-moc | 69 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 69 insertions(+)
 create mode 100755 scripts/replace-mops-moc

diff --git a/scripts/replace-mops-moc b/scripts/replace-mops-moc
new file mode 100755
index 00000000000..af2ab71cbd4
--- /dev/null
+++ b/scripts/replace-mops-moc
@@ -0,0 +1,69 @@
+#!/usr/bin/env bash
+# replace-mops-moc: Build moc via Nix and replace a mops-cached moc binary.
+# Usage: ./replace-mops-moc <mops-moc-version-dir> [restore]
+# - Without 'restore': builds .#release.moc, backs up existing 'moc' once as 'moc-backup' if absent,
+#   then installs the newly built 'moc' into the target version directory.
+# - With 'restore': moves 'moc-backup' back to 'moc' (overwriting current), then prints version.
+set -euo pipefail
+
+if [ "${1:-}" = "" ]; then
+  echo "Usage: $0 <mops-moc-version-dir> [restore]" >&2
+  echo "Example replace: $0 0.16.1" >&2
+  echo "Example restore: $0 0.16.1 restore" >&2
+  exit 2
+fi
+
+VERSION_DIR="$1"
+TARGET_DIR="${HOME}/Library/Caches/mops/moc/${VERSION_DIR}"
+TARGET="${TARGET_DIR}/moc"
+BACKUP="${TARGET}-backup"
+MODE="${2:-}"
+
+# Do not create directories; assume they exist as requested.
+if [ ! -d "${TARGET_DIR}" ]; then
+  echo "Error: Target directory does not exist: ${TARGET_DIR}" >&2
+  exit 1
+fi
+
+if [ "${MODE}" = "restore" ]; then
+  echo "Restoring backup for ${TARGET}"
+  if [ ! -f "${BACKUP}" ]; then
+    echo "Error: No backup found at ${BACKUP}" >&2
+    exit 1
+  fi
+  mv -f "${BACKUP}" "${TARGET}"
+  chmod +x "${TARGET}" || true
+  echo "Restored. Version:"
+  "${TARGET}" --version || true
+  exit 0
+fi
+
+echo "Building moc via Nix (.#release.moc)..."
+OUT_PATH="$(nix build --max-jobs 1 .#release.moc --print-out-paths)"
+SRC="${OUT_PATH}/bin/moc"
+
+echo "Using built moc at: ${SRC}"
+echo "Target directory: ${TARGET_DIR}"
+echo "Target binary: ${TARGET}"
+
+# Step 1: Backup existing moc if no backup exists yet
+if [ -f "${BACKUP}" ]; then
+  echo "Backup already exists at ${BACKUP}; skipping backup."
+else
+  if [ -f "${TARGET}" ]; then
+    echo "Creating backup at ${BACKUP}"
+    mv "${TARGET}" "${BACKUP}"
+  else
+    echo "No existing moc found at ${TARGET}; nothing to back up."
+  fi
+fi
+
+# Step 2: Replace moc with newly built one
+echo "Installing new moc to ${TARGET}"
+cp -f "${SRC}" "${TARGET}"
+chmod +x "${TARGET}"
+
+echo "Installed. Version:"
+"${TARGET}" --version || true
+
+

From 552f8344783ec7930dda102221da3ad450307014 Mon Sep 17 00:00:00 2001
From: Kamil Listopad <listopadkamil@gmail.com>
Date: Tue, 16 Sep 2025 13:02:43 +0200
Subject: [PATCH 15/22] fix draft tag to match the version + suffix

---
 .github/workflows/release.yml | 27 ++++++++++++++-------------
 1 file changed, 14 insertions(+), 13 deletions(-)

diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index ddbd8ed0d53..a9d124b7c05 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -6,12 +6,12 @@ on:
       - "*"
   workflow_dispatch:
     # To test this workflow: Go to Actions -> release -> Run workflow
-    # Or using the CLI: gh workflow run release --ref <branch> -f version=test-draft-release
+    # Or using the CLI: gh workflow run release --ref <branch> -f version_suffix=test-draft-release
     # This creates a draft release tagged with the specified version
     # Remember to delete the draft release after testing!
     inputs:
-      version:
-        description: "Version for draft release (default: test-draft-release)"
+      version_suffix:
+        description: "Suffix for draft release tag (e.g., experimental-foo-2)"
         required: false
         default: test-draft-release
         type: string
@@ -19,24 +19,22 @@ on:
 jobs:
   prepare:
     runs-on: ubuntu-latest
-    outputs:
-      version: ${{ inputs.version || github.ref_name }}
     steps:
       - name: Prepare release
-        run: echo "Preparing release for version ${{ inputs.version || github.ref_name }}"
+        run: echo "Preparing release ref=${{ github.ref_name }} suffix=${{ inputs.version_suffix }}"
 
       - name: Validate draft suffix (workflow_dispatch only)
         if: ${{ github.event_name == 'workflow_dispatch' }}
         run: |
           set -eu
-          SUFFIX="${{ inputs.version }}"
+          SUFFIX="${{ inputs.version_suffix }}"
           if [ -z "${SUFFIX:-}" ]; then
-            echo "Error: inputs.version (draft suffix) is empty"
+            echo "Error: inputs.version_suffix (draft suffix) is empty"
             exit 1
           fi
           # Allow only letters, digits, and hyphens
           if ! printf '%s' "${SUFFIX}" | grep -Eq '^[A-Za-z0-9-]+$'; then
-            echo "Error: inputs.version must contain only letters, digits, and hyphens (e.g., experimental-foo-2)"
+            echo "Error: inputs.version_suffix must contain only letters, digits, and hyphens (e.g., experimental-foo-2)"
             exit 1
           fi
 
@@ -52,7 +50,7 @@ jobs:
         id: read_changelog
         uses: ./.github/actions/extract-changelog
         with:
-          version: ${{ needs.prepare.outputs.version }}
+          version: ${{ github.ref_name }}
     outputs:
       release_body: ${{ steps.read_changelog.outputs.release_body }}
 
@@ -62,7 +60,7 @@ jobs:
       matrix:
         os: [ubuntu-latest, macos-13, ubuntu-24.04-arm, macos-latest]
     concurrency:
-      group: release-build-${{ matrix.os }}-${{ needs.prepare.outputs.version }}
+      group: release-build-${{ matrix.os }}-${{ github.ref_name }}
       cancel-in-progress: true
     runs-on: ${{ matrix.os }}
     steps:
@@ -102,9 +100,10 @@ jobs:
           merge-multiple: true
 
       - name: Rewrite artifact filenames with draft suffix
+        id: rewrite_draft_assets
         if: ${{ github.event_name == 'workflow_dispatch' }}
         env:
-          DRAFT_SUFFIX: ${{ inputs.version }}
+          DRAFT_SUFFIX: ${{ inputs.version_suffix }}
         run: |
           set -eu
           echo "Applying draft suffix: ${DRAFT_SUFFIX}"
@@ -128,6 +127,8 @@ jobs:
             [ -e "$f" ] || continue
             mv "$f" "${f%.tar.gz}-${DRAFT_SUFFIX}.tar.gz"
           done
+          # Expose computed draft tag as a step output
+          echo "tag=${version}-${DRAFT_SUFFIX}" >> "$GITHUB_OUTPUT"
 
       - name: List downloaded files
         run: |
@@ -138,7 +139,7 @@ jobs:
         uses: svenstaro/upload-release-action@v2
         with:
           repo_token: ${{ secrets.GITHUB_TOKEN }}
-          tag: ${{ needs.prepare.outputs.version }}
+          tag: ${{ github.event_name == 'workflow_dispatch' && steps.rewrite_draft_assets.outputs.tag || github.ref_name }}
           file: release-assets/*
           file_glob: true
           body: ${{ needs.changelog.outputs.release_body || 'Draft release created for testing purposes' }}

From c4d9368a915c5a5538862db7fb9659cd48ec976d Mon Sep 17 00:00:00 2001
From: Kamil Listopad <listopadkamil@gmail.com>
Date: Tue, 16 Sep 2025 14:03:02 +0200
Subject: [PATCH 16/22] refactor

---
 src/mo_frontend/typing.ml |  5 -----
 src/mo_types/type.ml      | 45 ++++++++++++++++++---------------------
 2 files changed, 21 insertions(+), 29 deletions(-)

diff --git a/src/mo_frontend/typing.ml b/src/mo_frontend/typing.ml
index 1665656fe73..294921e9934 100644
--- a/src/mo_frontend/typing.ml
+++ b/src/mo_frontend/typing.ml
@@ -1697,10 +1697,6 @@ and infer_exp'' env exp : T.typ =
     | _ -> ()
     end;
     let sort, ve = check_shared_pat env shared_pat in
-    (* let sort = match sort, !Mo_config.Flags.enhanced_orthogonal_persistence with
-    | T.Local T.Stable, false -> T.Local T.Flexible (* named local functions are flexible in classical mode *)
-    | _ -> sort
-    in *)
     let is_async = match typ_opt with
       | Some { it = AsyncT _; _ } -> true
       | _ -> false
@@ -1769,7 +1765,6 @@ and infer_exp'' env exp : T.typ =
       end
     end;
     let ts1 = match pat.it with TupP _ -> T.seq_of_tup t1 | _ -> [t1] in
-    (* let sort = if is_flexible && sort = T.Local T.Stable then T.Local T.Flexible else sort in *)
     T.Func (sort, c, T.close_binds cs tbs, List.map (T.close cs) ts1, List.map (T.close cs) ts2)
   | CallE (par_opt, exp1, inst, exp2) ->
     let t = infer_call env exp1 inst exp2 exp.at None in
diff --git a/src/mo_types/type.ml b/src/mo_types/type.ml
index 1c691ab50d2..ac53e517ce8 100644
--- a/src/mo_types/type.ml
+++ b/src/mo_types/type.ml
@@ -1592,21 +1592,22 @@ let rec combine rel lubs glbs t1 t2 =
     | Obj (s1, tf1), Obj (s2, tf2) when s1 = s2 ->
       (try Obj (s1, combine_fields rel lubs glbs tf1 tf2)
       with Mismatch -> assert (rel == glbs); Non)
-    | Func (s1, c1, bs1, ts11, ts12), Func (s2, c2, bs2, ts21, ts22) when
-        combine_sort rel lubs glbs s1 s2 bs1 bs2 <> None &&
-        c1 = c2 && eq_binds bs1 bs2 &&
-        List.(length ts11 = length ts21 && length ts12 = length ts22) ->
-      let ts = open_binds bs1 in
-      let cs = List.map (fun t -> fst (as_con t)) ts in
-      let opened = List.map (open_ ts) in
-      let closed = List.map (close cs) in
-      let rel' = if rel == lubs then glbs else lubs in
-      let s = Option.get (combine_sort rel lubs glbs s1 s2 bs1 bs2) in
-      Func (
-        s, c1, bs1,
-        closed (List.map2 (combine rel' lubs glbs) (opened ts11) (opened ts21)),
-        closed (List.map2 (combine rel lubs glbs) (opened ts12) (opened ts22))
-      )
+    | Func (s1, c1, bs1, ts11, ts12), Func (s2, c2, bs2, ts21, ts22) ->
+      begin match combine_sort rel lubs glbs s1 s2 bs1 bs2 with
+      | Some s when c1 = c2 && eq_binds bs1 bs2 &&
+          List.(length ts11 = length ts21 && length ts12 = length ts22) ->
+        let ts = open_binds bs1 in
+        let cs = List.map (fun t -> fst (as_con t)) ts in
+        let opened = List.map (open_ ts) in
+        let closed = List.map (close cs) in
+        let rel' = if rel == lubs then glbs else lubs in
+        Func (
+          s, c1, bs1,
+          closed (List.map2 (combine rel' lubs glbs) (opened ts11) (opened ts21)),
+          closed (List.map2 (combine rel lubs glbs) (opened ts12) (opened ts22))
+        )
+      | _ -> if rel == lubs then Any else Non
+      end
     | Async (s1, t11, t12), Async (s2, t21, t22) when s1 == s2 && eq t11 t21 ->
       Async (s1, t11, combine rel lubs glbs t12 t22)
     | Con _, _
@@ -1649,16 +1650,12 @@ let rec combine rel lubs glbs t1 t2 =
     | _, _ ->
       if rel == lubs then Any else Non
 
-and combine_sort rel lubs glbs s1 s2 bs1 bs2=
+and combine_sort rel lubs glbs s1 s2 bs1 bs2 =
   if s1 = s2 then Some s1 else
-  let both s = 
-    if rel_sort s1 s bs1 && rel_sort s2 s bs2 then Some s
-   else None
-  in
-  if rel == lubs then
-    both (Local Flexible)
-  else
-    both (Local Stable)
+  if rel == glbs then None else
+  let s = Local Flexible in
+  if rel_sort s1 s bs1 && rel_sort s2 s bs2 then Some s
+  else None
 
 and cons_if b x xs = if b then x::xs else xs
 

From 76c62d280ce7028981c5070ab327e1b06cb1a089 Mon Sep 17 00:00:00 2001
From: Kamil Listopad <listopadkamil@gmail.com>
Date: Tue, 16 Sep 2025 14:05:44 +0200
Subject: [PATCH 17/22] restore motoko-core branch

---
 flake.lock | 7 +++----
 flake.nix  | 2 +-
 2 files changed, 4 insertions(+), 5 deletions(-)

diff --git a/flake.lock b/flake.lock
index c6b156a6d51..d39bb2b6898 100644
--- a/flake.lock
+++ b/flake.lock
@@ -137,16 +137,15 @@
     "motoko-core-src": {
       "flake": false,
       "locked": {
-        "lastModified": 1757337895,
-        "narHash": "sha256-G5BlQfm/TJ0Trk5owOGDOTxoigcf5ErgnSEDyPe20fk=",
+        "lastModified": 1756913868,
+        "narHash": "sha256-zLJShje+X/+4yM0wTwNB9Bri00SH6G3vOvyUP56KdwU=",
         "owner": "dfinity",
         "repo": "motoko-core",
-        "rev": "59310bfed843c072882ad48980a366fb87f19f03",
+        "rev": "e397d7e577491703d94a1f82dc88ff01c59c0dbd",
         "type": "github"
       },
       "original": {
         "owner": "dfinity",
-        "ref": "luc/oo-data-structures",
         "repo": "motoko-core",
         "type": "github"
       }
diff --git a/flake.nix b/flake.nix
index 67843862985..0489f9d7e63 100644
--- a/flake.nix
+++ b/flake.nix
@@ -46,7 +46,7 @@
       flake = false;
     };
     motoko-core-src = {
-      url = "github:dfinity/motoko-core/luc/oo-data-structures";
+      url = "github:dfinity/motoko-core";
       flake = false;
     };
     motoko-matchers-src = {

From 11340ce82f77096efa5f5e01561e1c713d8eaf82 Mon Sep 17 00:00:00 2001
From: Kamil Listopad <listopadkamil@gmail.com>
Date: Tue, 16 Sep 2025 14:09:54 +0200
Subject: [PATCH 18/22] tmp disable macos-13

---
 .github/workflows/release.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index a9d124b7c05..8906f3afa93 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -58,7 +58,7 @@ jobs:
     needs: prepare
     strategy:
       matrix:
-        os: [ubuntu-latest, macos-13, ubuntu-24.04-arm, macos-latest]
+        os: [ubuntu-latest, ubuntu-24.04-arm, macos-latest]
     concurrency:
       group: release-build-${{ matrix.os }}-${{ github.ref_name }}
       cancel-in-progress: true

From 62131d6c4dc03790c1de280adca68b13cf5ec16c Mon Sep 17 00:00:00 2001
From: Kamil Listopad <listopadkamil@gmail.com>
Date: Tue, 16 Sep 2025 15:48:55 +0200
Subject: [PATCH 19/22] rel_func_sort ~eq and sub_func_sort

---
 src/mo_frontend/bi_match.ml |  2 +-
 src/mo_types/type.ml        | 13 ++++++++-----
 src/mo_types/type.mli       |  4 +++-
 3 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/src/mo_frontend/bi_match.ml b/src/mo_frontend/bi_match.ml
index 60f2bc6a0a4..bff5f308910 100644
--- a/src/mo_frontend/bi_match.ml
+++ b/src/mo_frontend/bi_match.ml
@@ -261,7 +261,7 @@ let bi_match_typs ctx =
     | Tup ts1, Tup ts2 ->
       bi_match_list bi_match_typ rel eq inst any ts1 ts2
     | Func (s1, c1, tbs1, t11, t12), Func (s2, c2, tbs2, t21, t22) ->
-      if rel_sort s1 s2 tbs1 && c1 = c2 then
+      if rel_func_sort ~eq:(rel == eq) s1 s2 tbs1 && c1 = c2 then
       (match bi_match_binds rel eq inst any tbs1 tbs2 with
        | Some (inst, ts) ->
          let any' = List.fold_right
diff --git a/src/mo_types/type.ml b/src/mo_types/type.ml
index ac53e517ce8..895ac9011d8 100644
--- a/src/mo_types/type.ml
+++ b/src/mo_types/type.ml
@@ -1223,7 +1223,7 @@ let rec rel_typ d rel eq t1 t2 =
   | Tup ts1, Tup ts2 ->
     rel_list "tuple arguments" d rel_typ rel eq ts1 ts2
   | Func (s1, c1, tbs1, t11, t12), Func (s2, c2, tbs2, t21, t22) ->
-    (rel_sort s1 s2 tbs1 || incompatible_func_sorts d t1 t2) &&
+    (rel_func_sort ~eq:(rel == eq) s1 s2 tbs1 || incompatible_func_sorts d t1 t2) &&
     (c1 = c2 || incompatible_bounds d t1 t2) &&
     (match rel_binds d eq eq tbs1 tbs2 with
      | Some ts ->
@@ -1238,7 +1238,10 @@ let rec rel_typ d rel eq t1 t2 =
   | _, _ -> incompatible_types d t1 t2
   end
 
-and rel_sort s1 s2 tbs1 =
+and rel_func_sort ~eq s1 s2 tbs1 =
+  if eq then s1 = s2 else sub_func_sort s1 s2 tbs1
+
+and sub_func_sort s1 s2 tbs1 =
   match s1, s2 with
   | Local Stable, Local Flexible -> 
     not (List.exists (fun b -> b.sort = Type) tbs1)
@@ -1593,7 +1596,7 @@ let rec combine rel lubs glbs t1 t2 =
       (try Obj (s1, combine_fields rel lubs glbs tf1 tf2)
       with Mismatch -> assert (rel == glbs); Non)
     | Func (s1, c1, bs1, ts11, ts12), Func (s2, c2, bs2, ts21, ts22) ->
-      begin match combine_sort rel lubs glbs s1 s2 bs1 bs2 with
+      begin match combine_func_sort rel lubs glbs s1 s2 bs1 bs2 with
       | Some s when c1 = c2 && eq_binds bs1 bs2 &&
           List.(length ts11 = length ts21 && length ts12 = length ts22) ->
         let ts = open_binds bs1 in
@@ -1650,11 +1653,11 @@ let rec combine rel lubs glbs t1 t2 =
     | _, _ ->
       if rel == lubs then Any else Non
 
-and combine_sort rel lubs glbs s1 s2 bs1 bs2 =
+and combine_func_sort rel lubs glbs s1 s2 bs1 bs2 =
   if s1 = s2 then Some s1 else
   if rel == glbs then None else
   let s = Local Flexible in
-  if rel_sort s1 s bs1 && rel_sort s2 s bs2 then Some s
+  if sub_func_sort s1 s bs1 && sub_func_sort s2 s bs2 then Some s
   else None
 
 and cons_if b x xs = if b then x::xs else xs
diff --git a/src/mo_types/type.mli b/src/mo_types/type.mli
index ca420945b4b..d7210c8090d 100644
--- a/src/mo_types/type.mli
+++ b/src/mo_types/type.mli
@@ -276,7 +276,9 @@ val eq_kind : ?src_fields : Field_sources.t -> kind -> kind -> bool
 val sub : ?src_fields : Field_sources.t -> typ -> typ -> bool
 val sub_explained : ?src_fields : Field_sources.t -> context -> typ -> typ -> compatibility
 val compatible : typ -> typ -> bool
-val rel_sort : func_sort -> func_sort -> bind list -> bool
+
+val rel_func_sort : eq:bool -> func_sort -> func_sort -> bind list -> bool
+val sub_func_sort : func_sort -> func_sort -> bind list -> bool
 
 exception PreEncountered
 val lub : ?src_fields : Field_sources.t -> typ -> typ -> typ

From 5028f5ada79466fe1e18d67a81813801843f681a Mon Sep 17 00:00:00 2001
From: Kamil Listopad <listopadkamil@gmail.com>
Date: Wed, 17 Sep 2025 10:10:43 +0200
Subject: [PATCH 20/22] remove done todo

---
 test/fail/persistent-func-type-argument-and-return.mo | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/test/fail/persistent-func-type-argument-and-return.mo b/test/fail/persistent-func-type-argument-and-return.mo
index e0038ac4edd..64deced5329 100644
--- a/test/fail/persistent-func-type-argument-and-return.mo
+++ b/test/fail/persistent-func-type-argument-and-return.mo
@@ -1,7 +1,7 @@
 module {
   persistent func g<T>(x : T) : persistent() -> T {
     persistent func h() : T { x };
-    h; // TODO: non-eop should still typecheck here
+    h;
   };
   // don't allow `func() {}` to typecheck as `persistent() -> ()` for now
   let h = g<persistent() -> ()>(func() {});

From b31e1a43b16c56d251e2ebd58fc30f9cfd315277 Mon Sep 17 00:00:00 2001
From: Kamil Listopad <listopadkamil@gmail.com>
Date: Wed, 17 Sep 2025 10:12:38 +0200
Subject: [PATCH 21/22] revert #5491, cleaunp

---
 .github/workflows/release.yml                 | 158 +++++++-----------
 scripts/replace-mops-moc                      |  69 --------
 ...-funcs-in-type-args-and-return.drun-run.ok |   2 -
 3 files changed, 57 insertions(+), 172 deletions(-)
 delete mode 100755 scripts/replace-mops-moc
 delete mode 100644 test/run-drun/ok/persistent-actor-with-persistent-funcs-in-type-args-and-return.drun-run.ok

diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index 8906f3afa93..ad56b69f5cf 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -3,15 +3,15 @@ name: release
 on:
   push:
     tags:
-      - "*"
+    - '*'
   workflow_dispatch:
     # To test this workflow: Go to Actions -> release -> Run workflow
-    # Or using the CLI: gh workflow run release --ref <branch> -f version_suffix=test-draft-release
+    # Or using the CLI: gh workflow run release --ref <branch> -f version=test-draft-release
     # This creates a draft release tagged with the specified version
     # Remember to delete the draft release after testing!
     inputs:
-      version_suffix:
-        description: "Suffix for draft release tag (e.g., experimental-foo-2)"
+      version:
+        description: 'Version for draft release (default: test-draft-release)'
         required: false
         default: test-draft-release
         type: string
@@ -19,38 +19,25 @@ on:
 jobs:
   prepare:
     runs-on: ubuntu-latest
+    outputs:
+      version: ${{ inputs.version || github.ref_name }}
     steps:
       - name: Prepare release
-        run: echo "Preparing release ref=${{ github.ref_name }} suffix=${{ inputs.version_suffix }}"
-
-      - name: Validate draft suffix (workflow_dispatch only)
-        if: ${{ github.event_name == 'workflow_dispatch' }}
-        run: |
-          set -eu
-          SUFFIX="${{ inputs.version_suffix }}"
-          if [ -z "${SUFFIX:-}" ]; then
-            echo "Error: inputs.version_suffix (draft suffix) is empty"
-            exit 1
-          fi
-          # Allow only letters, digits, and hyphens
-          if ! printf '%s' "${SUFFIX}" | grep -Eq '^[A-Za-z0-9-]+$'; then
-            echo "Error: inputs.version_suffix must contain only letters, digits, and hyphens (e.g., experimental-foo-2)"
-            exit 1
-          fi
+        run: echo "Preparing release for version ${{ inputs.version || github.ref_name }}"
 
   # Check that the changelog is in good order and extract the changelog.
   changelog:
     runs-on: ubuntu-latest
     needs: prepare
     steps:
-      - uses: actions/checkout@v5
-      - name: Extract changelog
-        # Skip this step for draft releases. Leave the release body empty.
-        if: ${{ github.event_name != 'workflow_dispatch' }}
-        id: read_changelog
-        uses: ./.github/actions/extract-changelog
-        with:
-          version: ${{ github.ref_name }}
+    - uses: actions/checkout@v5
+    - name: Extract changelog
+      # Skip this step for draft releases. Leave the release body empty.
+      if: ${{ github.event_name != 'workflow_dispatch' }}
+      id: read_changelog
+      uses: ./.github/actions/extract-changelog
+      with:
+        version: ${{ needs.prepare.outputs.version }}
     outputs:
       release_body: ${{ steps.read_changelog.outputs.release_body }}
 
@@ -58,90 +45,59 @@ jobs:
     needs: prepare
     strategy:
       matrix:
-        os: [ubuntu-latest, ubuntu-24.04-arm, macos-latest]
+        os: [ ubuntu-latest, macos-13, ubuntu-24.04-arm, macos-latest ]
     concurrency:
-      group: release-build-${{ matrix.os }}-${{ github.ref_name }}
+      group: release-build-${{ matrix.os }}-${{ needs.prepare.outputs.version }}
       cancel-in-progress: true
     runs-on: ${{ matrix.os }}
     steps:
-      - uses: actions/checkout@v5
-      - uses: cachix/install-nix-action@v31
-      - uses: cachix/cachix-action@v16
-        with:
-          name: ic-hs-test
-          # NB: No auth token, we don't expect to push new stuff here
+    - uses: actions/checkout@v5
+    - uses: cachix/install-nix-action@v31
+    - uses: cachix/cachix-action@v16
+      with:
+        name: ic-hs-test
+        # NB: No auth token, we don't expect to push new stuff here
 
-      - name: Build platform-specific release files
-        run: nix build --max-jobs 1 '.#"release-files-${{ matrix.os }}"'
+    - name: Build platform-specific release files
+      run: nix build --max-jobs 1 '.#"release-files-${{ matrix.os }}"'
 
-      - name: Upload Release Artifacts
-        uses: actions/upload-artifact@v4
-        with:
-          name: release-files-${{ matrix.os }}
-          path: result/*
+    - name: Upload Release Artifacts
+      uses: actions/upload-artifact@v4
+      with:
+        name: release-files-${{ matrix.os }}
+        path: result/*
 
-      - name: Test release files
-        run: |
-          uname -s -m
-          moc="$(nix build --max-jobs 1 .#release.moc --print-out-paths)"
-          "$moc/bin/moc" --version
-          file "$moc/bin/moc"
-          ldd "$moc/bin/moc" || true
+    - name: Test release files
+      run: |
+        uname -s -m
+        moc="$(nix build --max-jobs 1 .#release.moc --print-out-paths)"
+        "$moc/bin/moc" --version
+        file "$moc/bin/moc"
+        ldd "$moc/bin/moc" || true
 
   publish:
     runs-on: ubuntu-latest
     needs: [prepare, changelog, build]
     steps:
-      - name: Download all release artifacts
-        uses: actions/download-artifact@v5
-        with:
-          path: release-assets
-          pattern: release-files-*
-          merge-multiple: true
-
-      - name: Rewrite artifact filenames with draft suffix
-        id: rewrite_draft_assets
-        if: ${{ github.event_name == 'workflow_dispatch' }}
-        env:
-          DRAFT_SUFFIX: ${{ inputs.version_suffix }}
-        run: |
-          set -eu
-          echo "Applying draft suffix: ${DRAFT_SUFFIX}"
-          dir="release-assets"
-          # Extract numeric version from moc-<version>.js
-          version="$(ls "$dir"/moc-*.js 2>/dev/null | sed -n 's#.*moc-\([0-9.]\+\)\.js#\1#p' | head -n1 || true)"
-          if [ -z "${version}" ]; then
-            echo "Could not determine base version from moc-*.js; skipping rename."
-            exit 0
-          fi
-          echo "Detected base version: ${version}"
-          # Rename JS artifacts
-          if [ -f "$dir/moc-${version}.js" ]; then
-            mv "$dir/moc-${version}.js" "$dir/moc-${version}-${DRAFT_SUFFIX}.js"
-          fi
-          if [ -f "$dir/moc-interpreter-${version}.js" ]; then
-            mv "$dir/moc-interpreter-${version}.js" "$dir/moc-interpreter-${version}-${DRAFT_SUFFIX}.js"
-          fi
-          # Rename tarballs
-          for f in "$dir"/*-"${version}".tar.gz; do
-            [ -e "$f" ] || continue
-            mv "$f" "${f%.tar.gz}-${DRAFT_SUFFIX}.tar.gz"
-          done
-          # Expose computed draft tag as a step output
-          echo "tag=${version}-${DRAFT_SUFFIX}" >> "$GITHUB_OUTPUT"
+    - name: Download all release artifacts
+      uses: actions/download-artifact@v5
+      with:
+        path: release-assets
+        pattern: release-files-*
+        merge-multiple: true
 
-      - name: List downloaded files
-        run: |
-          echo "Contents of release-assets directory:"
-          find release-assets -type f -ls || true
+    - name: List downloaded files
+      run: |
+        echo "Contents of release-assets directory:"
+        find release-assets -type f -ls || true
 
-      - name: Upload Release Assets
-        uses: svenstaro/upload-release-action@v2
-        with:
-          repo_token: ${{ secrets.GITHUB_TOKEN }}
-          tag: ${{ github.event_name == 'workflow_dispatch' && steps.rewrite_draft_assets.outputs.tag || github.ref_name }}
-          file: release-assets/*
-          file_glob: true
-          body: ${{ needs.changelog.outputs.release_body || 'Draft release created for testing purposes' }}
-          draft: ${{ github.event_name == 'workflow_dispatch' }}
-          prerelease: ${{ github.event_name == 'workflow_dispatch' }}
+    - name: Upload Release Assets
+      uses: svenstaro/upload-release-action@v2
+      with:
+        repo_token: ${{ secrets.GITHUB_TOKEN }}
+        tag: ${{ needs.prepare.outputs.version }}
+        file: release-assets/*
+        file_glob: true
+        body: ${{ needs.changelog.outputs.release_body || 'Draft release created for testing purposes' }}
+        draft: ${{ github.event_name == 'workflow_dispatch' }}
+        prerelease: ${{ github.event_name == 'workflow_dispatch' }}
diff --git a/scripts/replace-mops-moc b/scripts/replace-mops-moc
deleted file mode 100755
index af2ab71cbd4..00000000000
--- a/scripts/replace-mops-moc
+++ /dev/null
@@ -1,69 +0,0 @@
-#!/usr/bin/env bash
-# replace-mops-moc: Build moc via Nix and replace a mops-cached moc binary.
-# Usage: ./replace-mops-moc <mops-moc-version-dir> [restore]
-# - Without 'restore': builds .#release.moc, backs up existing 'moc' once as 'moc-backup' if absent,
-#   then installs the newly built 'moc' into the target version directory.
-# - With 'restore': moves 'moc-backup' back to 'moc' (overwriting current), then prints version.
-set -euo pipefail
-
-if [ "${1:-}" = "" ]; then
-  echo "Usage: $0 <mops-moc-version-dir> [restore]" >&2
-  echo "Example replace: $0 0.16.1" >&2
-  echo "Example restore: $0 0.16.1 restore" >&2
-  exit 2
-fi
-
-VERSION_DIR="$1"
-TARGET_DIR="${HOME}/Library/Caches/mops/moc/${VERSION_DIR}"
-TARGET="${TARGET_DIR}/moc"
-BACKUP="${TARGET}-backup"
-MODE="${2:-}"
-
-# Do not create directories; assume they exist as requested.
-if [ ! -d "${TARGET_DIR}" ]; then
-  echo "Error: Target directory does not exist: ${TARGET_DIR}" >&2
-  exit 1
-fi
-
-if [ "${MODE}" = "restore" ]; then
-  echo "Restoring backup for ${TARGET}"
-  if [ ! -f "${BACKUP}" ]; then
-    echo "Error: No backup found at ${BACKUP}" >&2
-    exit 1
-  fi
-  mv -f "${BACKUP}" "${TARGET}"
-  chmod +x "${TARGET}" || true
-  echo "Restored. Version:"
-  "${TARGET}" --version || true
-  exit 0
-fi
-
-echo "Building moc via Nix (.#release.moc)..."
-OUT_PATH="$(nix build --max-jobs 1 .#release.moc --print-out-paths)"
-SRC="${OUT_PATH}/bin/moc"
-
-echo "Using built moc at: ${SRC}"
-echo "Target directory: ${TARGET_DIR}"
-echo "Target binary: ${TARGET}"
-
-# Step 1: Backup existing moc if no backup exists yet
-if [ -f "${BACKUP}" ]; then
-  echo "Backup already exists at ${BACKUP}; skipping backup."
-else
-  if [ -f "${TARGET}" ]; then
-    echo "Creating backup at ${BACKUP}"
-    mv "${TARGET}" "${BACKUP}"
-  else
-    echo "No existing moc found at ${TARGET}; nothing to back up."
-  fi
-fi
-
-# Step 2: Replace moc with newly built one
-echo "Installing new moc to ${TARGET}"
-cp -f "${SRC}" "${TARGET}"
-chmod +x "${TARGET}"
-
-echo "Installed. Version:"
-"${TARGET}" --version || true
-
-
diff --git a/test/run-drun/ok/persistent-actor-with-persistent-funcs-in-type-args-and-return.drun-run.ok b/test/run-drun/ok/persistent-actor-with-persistent-funcs-in-type-args-and-return.drun-run.ok
deleted file mode 100644
index a6f776f43c6..00000000000
--- a/test/run-drun/ok/persistent-actor-with-persistent-funcs-in-type-args-and-return.drun-run.ok
+++ /dev/null
@@ -1,2 +0,0 @@
-ingress Completed: Reply: 0x4449444c016c01b3c4b1f204680100010a00000000000000000101
-ingress Completed: Reply: 0x4449444c0000

From 636b15a44cd89072ce0d36a0e263d5d623e4d45d Mon Sep 17 00:00:00 2001
From: Kamil Listopad <listopadkamil@gmail.com>
Date: Wed, 17 Sep 2025 10:25:35 +0200
Subject: [PATCH 22/22] damn you run.sh and your extra moc args...

---
 ...or-with-persistent-funcs-in-type-args-and-return.drun-run.ok | 2 ++
 1 file changed, 2 insertions(+)
 create mode 100644 test/run-drun/ok/persistent-actor-with-persistent-funcs-in-type-args-and-return.drun-run.ok

diff --git a/test/run-drun/ok/persistent-actor-with-persistent-funcs-in-type-args-and-return.drun-run.ok b/test/run-drun/ok/persistent-actor-with-persistent-funcs-in-type-args-and-return.drun-run.ok
new file mode 100644
index 00000000000..a6f776f43c6
--- /dev/null
+++ b/test/run-drun/ok/persistent-actor-with-persistent-funcs-in-type-args-and-return.drun-run.ok
@@ -0,0 +1,2 @@
+ingress Completed: Reply: 0x4449444c016c01b3c4b1f204680100010a00000000000000000101
+ingress Completed: Reply: 0x4449444c0000