From 7a05912c3bc3a95ef0ec7379d215604b7ea7e521 Mon Sep 17 00:00:00 2001
From: Vladimir Davydov <vdavydov@tarantool.org>
Date: Wed, 2 Apr 2025 18:43:39 +0300
Subject: [PATCH 01/14] cmake: bump min version to 3.5

Compatibility with CMake < 3.5 has been removed from CMake.
---
 CMakeLists.txt | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 2025061..afae120 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 2.6 FATAL_ERROR)
+cmake_minimum_required(VERSION 3.5 FATAL_ERROR)
 
 project(checks NONE)
 

From 1c7a8346fe573f65172b522206b5940fe5a71e23 Mon Sep 17 00:00:00 2001
From: Alexey Potapenko <a.potapenko@vkteam.ru>
Date: Wed, 2 Apr 2025 09:33:45 +0300
Subject: [PATCH 02/14] ci: bump ubuntu version

This patch bumps actions to use ubuntu-24.04 for fixing the following GitHub
warning:

    The Ubuntu 20.04 Actions runner image will begin deprecation
    on 2025-02-01.

Part of #TNTP-1918
Closes #64
---
 .github/workflows/packaging.yml        | 10 ++++++----
 .github/workflows/push_rockspec.yml    |  6 +++---
 .github/workflows/reusable_testing.yml |  4 ++--
 .github/workflows/test.yml             | 12 ++++++------
 CMakeLists.txt                         |  2 +-
 debian/prebuild.sh                     | 11 ++++++++++-
 6 files changed, 28 insertions(+), 17 deletions(-)

diff --git a/.github/workflows/packaging.yml b/.github/workflows/packaging.yml
index 1bf02ea..8c6fee2 100644
--- a/.github/workflows/packaging.yml
+++ b/.github/workflows/packaging.yml
@@ -15,7 +15,7 @@ jobs:
     if: |
       github.event_name == 'push' ||
       github.event.pull_request.head.repo.full_name != github.repository
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-24.04
     steps:
       - name: Check module version
         if: ${{ github.event_name == 'push' && startsWith(github.ref, 'refs/tags/') }}
@@ -32,7 +32,7 @@ jobs:
       github.event_name == 'push' ||
       github.event.pull_request.head.repo.full_name != github.repository
     needs: version-check
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-24.04
 
     strategy:
       fail-fast: false
@@ -41,6 +41,7 @@ jobs:
           - { os: 'debian', dist: 'stretch' }
           - { os: 'debian', dist: 'buster' }
           - { os: 'debian', dist: 'bullseye' }
+          - { os: 'debian', dist: 'bookworm' }
           - { os: 'el', dist: '7' }
           - { os: 'el', dist: '8' }
           - { os: 'fedora', dist: '30' }
@@ -54,6 +55,7 @@ jobs:
           - { os: 'ubuntu', dist: 'bionic' }
           - { os: 'ubuntu', dist: 'focal' }
           - { os: 'ubuntu', dist: 'jammy' }
+          - { os: 'ubuntu', dist: 'noble' }
 
     env:
       OS: ${{ matrix.platform.os }}
@@ -61,12 +63,12 @@ jobs:
 
     steps:
       - name: Clone the module
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           fetch-depth: 0
 
       - name: Clone the packpack tool
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           repository: packpack/packpack
           path: packpack
diff --git a/.github/workflows/push_rockspec.yml b/.github/workflows/push_rockspec.yml
index ae3e383..381c689 100644
--- a/.github/workflows/push_rockspec.yml
+++ b/.github/workflows/push_rockspec.yml
@@ -17,7 +17,7 @@ jobs:
   version-check:
     # We need this job to run only on push with tag.
     if: ${{ github.event_name == 'push' && startsWith(github.ref, 'refs/tags/') }}
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-24.04
     steps:
       - name: Check module version
         uses: tarantool/actions/check-module-version@master
@@ -27,7 +27,7 @@ jobs:
             require('test.rock_utils').assert_nonbuiltin('checks')
 
   push-scm-rockspec:
-    runs-on: [ ubuntu-20.04 ]
+    runs-on: [ ubuntu-24.04 ]
     if: github.ref == 'refs/heads/master' && github.event.workflow_run.conclusion == 'success'
     steps:
       - uses: actions/checkout@master
@@ -38,7 +38,7 @@ jobs:
           files: ${{ env.ROCK_NAME }}-scm-1.rockspec
 
   push-tagged-rockspec:
-    runs-on: [ ubuntu-20.04 ]
+    runs-on: [ ubuntu-24.04 ]
     if: startsWith(github.ref, 'refs/tags')
     needs: version-check
     steps:
diff --git a/.github/workflows/reusable_testing.yml b/.github/workflows/reusable_testing.yml
index efe987f..518408a 100644
--- a/.github/workflows/reusable_testing.yml
+++ b/.github/workflows/reusable_testing.yml
@@ -5,13 +5,13 @@ on:
     inputs:
       artifact_name:
         description: The name of the tarantool build artifact
-        default: ubuntu-focal
+        default: ubuntu-jammy
         required: false
         type: string
 
 jobs:
   run_tests:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-24.04
     steps:
       - name: Clone the checks module
         uses: actions/checkout@v4
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 3e46f23..5c489c2 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -8,12 +8,12 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        tarantool: ['1.10', '2.5', '2.6', '2.7', '2.8', '2.10']
+        tarantool: ['1.10','2.11', '3.3']
 
-    runs-on: [ubuntu-20.04]
+    runs-on: [ubuntu-22.04]
     steps:
-      - uses: actions/checkout@v3
-      - uses: tarantool/setup-tarantool@v2
+      - uses: actions/checkout@v4
+      - uses: tarantool/setup-tarantool@v3
         with:
           tarantool-version: ${{ matrix.tarantool }}
 
@@ -36,9 +36,9 @@ jobs:
     strategy:
       fail-fast: false
 
-    runs-on: [ubuntu-20.04]
+    runs-on: [ubuntu-22.04]
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - name: Setup LuaJIT
         run: sudo apt install -y luajit
diff --git a/CMakeLists.txt b/CMakeLists.txt
index afae120..ff0de26 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.5 FATAL_ERROR)
+cmake_minimum_required(VERSION 3.20 FATAL_ERROR)
 
 project(checks NONE)
 
diff --git a/debian/prebuild.sh b/debian/prebuild.sh
index ecc64d2..3f2a4be 100755
--- a/debian/prebuild.sh
+++ b/debian/prebuild.sh
@@ -2,4 +2,13 @@
 
 set -e -o pipefail
 
-curl -LsSf https://www.tarantool.io/release/1.10/installer.sh | sudo bash
+if [[ $DIST == "noble" ]] || [[ $DIST == "bookworm" ]]; then
+  curl -LsSf https://www.tarantool.io/release/3/installer.sh | sudo bash
+elif [[ $DIST == "impish" ]] || [[ $DIST == "jammy" ]]; then
+  curl -LsSf https://www.tarantool.io/release/2/installer.sh | sudo bash
+else
+  curl -LsSf https://www.tarantool.io/release/1.10/installer.sh | sudo bash
+fi
+
+sudo apt install -y tt
+tt version

From 990334c2c6484806be17a70d44bd8d33f23bee63 Mon Sep 17 00:00:00 2001
From: Alexey Potapenko <a.potapenko@vkteam.ru>
Date: Fri, 4 Apr 2025 16:09:28 +0300
Subject: [PATCH 03/14] ci: set cmake policy version

---
 CMakeLists.txt | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index ff0de26..ef330dd 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.20 FATAL_ERROR)
+cmake_minimum_required(VERSION 3.10...3.31 FATAL_ERROR)
 
 project(checks NONE)
 

From c3641e71505c313b8f101ac0a0267d56f0e1b5ce Mon Sep 17 00:00:00 2001
From: Alexey Potapenko <a.potapenko@vkteam.ru>
Date: Tue, 21 Oct 2025 11:58:04 +0300
Subject: [PATCH 04/14] Release 3.4.0

---
 CHANGELOG.md       | 20 ++++++++++++++++++++
 checks/version.lua |  2 +-
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index b66ea7b..903bb80 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,25 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
 and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.html).
 
+## [Unreleased]
+
+### Added
+
+### Changed
+
+### Fixed
+
+### Removed
+
+## [3.4.0] - 2025-10-21
+
+This release introduces bumped CMake version to avoid compatibility
+problem with CMake 4.x.
+
+### Changed
+
+- Bump CMake version to avoid compatibility problem with CMake 4.x (#66).
+
 ## [3.3.0] - 2023-04-19
 
 ### Added
@@ -16,6 +35,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Override built-in checks, if installed.
 
 ## [3.2.0] - 2023-01-27
+
 ### Added
 
 - "error" type supported.
diff --git a/checks/version.lua b/checks/version.lua
index 37ef5c9..a37cd51 100644
--- a/checks/version.lua
+++ b/checks/version.lua
@@ -1,4 +1,4 @@
 -- Сontains the module version.
 -- Requires manual update in case of release commit.
 
-return '3.3.0'
+return '3.4.0'

From 70567395ba43ae58569c3184a358b17b192db937 Mon Sep 17 00:00:00 2001
From: Sergey Bronnikov <sergeyb@tarantool.org>
Date: Fri, 7 Aug 2026 17:21:41 +0300
Subject: [PATCH 05/14] test: update luacheckrc

The patch updates luacheckrc to suppress warnings.
Follows up the commit 49fa005dab08a1b206771e89e5231f779cccf914
("test: add linting stage").
---
 .luacheckrc | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/.luacheckrc b/.luacheckrc
index 57c02f0..7f11a70 100644
--- a/.luacheckrc
+++ b/.luacheckrc
@@ -2,3 +2,12 @@ include_files = {'**/*.lua', '*.luacheckrc', '*.rockspec'}
 exclude_files = {'.rocks/', 'tmp/', 'build/'}
 max_line_length = 120
 redefined = false
+globals = {
+    "box",
+}
+ignore = {
+    -- Accessing an undefined field of a global variable <table>.
+    "143/table",
+    -- Unused variable with `_` prefix.
+    "212/_.*",
+}

From 41af70f5fbf5100e7c580ca7567f6cc3a160b313 Mon Sep 17 00:00:00 2001
From: Sergey Bronnikov <sergeyb@tarantool.org>
Date: Fri, 7 Aug 2026 12:49:22 +0300
Subject: [PATCH 06/14] doc: document public Lua functions with EmmyLua

The patch adds comments for functions with descriptions
and argument types in EmmyLua format.

Needed for tarantool/tarantool#13020
---
 checks.lua | 111 +++++++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 103 insertions(+), 8 deletions(-)

diff --git a/checks.lua b/checks.lua
index 35060a8..434e1e4 100644
--- a/checks.lua
+++ b/checks.lua
@@ -1,3 +1,15 @@
+---The `checks` module provides the ability to check the types of arguments
+---passed to a Lua function. It is designed to reveal mistakes in code, not to
+---validate user input.
+---
+---The module table itself is callable: `checks(type_1, ...)` is equivalent to
+---`checks.checks(type_1, ...)`.
+---
+---@alias checks.qualifier string|table<any, checks.qualifier>
+---
+---@class checks
+---@field checks fun(...: checks.qualifier) Checks the arguments of the calling function.
+---@field _VERSION string The module version.
 local ffi = require('ffi')
 
 ffi.cdef[[
@@ -18,14 +30,14 @@ local _qualifiers_cache = {
     -- },
 }
 
---- Check that string (or substring) starts with given string
--- Optionally restricting the matching with the given offsets
--- @function startswith
--- @string    inp     original string
--- @string    head    the substring to check against
--- @int[opt]  _start  start index of matching boundary
--- @int[opt]  _end    end index of matching boundary
--- @returns           boolean
+---Check that the given string (or substring) starts with the given string,
+---optionally restricting the matching with the given offsets.
+---
+---@param inp string The original string.
+---@param head string The substring to check against.
+---@param _start? integer Start index of the matching boundary (default: `1`).
+---@param _end? integer End index of the matching boundary (default: `#inp`).
+---@return boolean `true` if `inp` starts with `head`, `false` otherwise.
 local function startswith(inp, head, _start, _end)
     if type(inp) ~= 'string' then
         error(err_string_arg:format(1, 'string.startswith', 'string',
@@ -69,6 +81,13 @@ local function startswith(inp, head, _start, _end)
 end
 
 
+---Check that a value conforms to the given string type qualifier.
+---
+---@param value any The value to check.
+---@param expected_type string The string type qualifier, e.g. `'string'`,
+---    `'?number|string'`, or `'?'` for any type.
+---@return boolean? `true` if the value conforms to the type qualifier.
+---@return string? error_message The formatted error message if the check fails.
 local function check_string_type(value, expected_type)
     -- 1. Check any value.
     if expected_type == '?' then
@@ -123,6 +142,11 @@ local function check_string_type(value, expected_type)
     )
 end
 
+---Format a table key for an error message: `.key` for strings and `[n]`
+---for numbers.
+---
+---@param key any The table key.
+---@return string The formatted key name.
 local function keyname_fmt(key)
     if type(key) == 'string' then
         return string.format('.%s', key)
@@ -133,6 +157,12 @@ local function keyname_fmt(key)
     end
 end
 
+---Check that a table conforms to the given table type qualifier.
+---
+---@param tbl table? The table to check.
+---@param expected_fields table<any, checks.qualifier> The table type qualifier.
+---@return boolean? `true` if the table conforms to the type qualifier.
+---@return string? error_message The formatted error message if the check fails.
 local function check_table_type(tbl, expected_fields)
     if tbl == nil then
         tbl = nil
@@ -187,6 +217,17 @@ local function check_table_type(tbl, expected_fields)
     return true
 end
 
+---Checks that the arguments of the calling function conform to the specified
+---types. Must be called at the top of the function being checked; each type
+---qualifier corresponds to the argument at the same position.
+---
+---String qualifiers check Lua types, Tarantool-specific types (`uint64`,
+---`int64`, `decimal`, `uuid`, etc.), metatable `__type` values, and custom
+---checker names; they can be combined into union types (`'number|string'`) and
+---made optional (`'?string'`). Table qualifiers validate the values of a table
+---argument.
+---
+---@param ... checks.qualifier Type qualifiers, one per argument to check.
 local function checks(...)
     local skip = 0
 
@@ -249,15 +290,41 @@ local function checks(...)
     end
 end
 
+---The `checks` function is also available as a global, so it can be used
+---without loading the module (Tarantool 2.11.0 and later).
 rawset(_G, 'checks', checks)
 
+---The `checkers` global table provides access to checkers for different types.
+---It can be extended with custom checkers that perform arbitrary validations.
+---
+---@class checks.checkers
+---@field datetime fun(arg: any): boolean Check that the value is a datetime object.
+---@field decimal fun(arg: any): boolean Check that the value has the decimal type.
+---@field error fun(arg: any): boolean Check that the value is an error object.
+---@field int64 fun(arg: any): boolean Check that the value is an int64 value.
+---@field interval fun(arg: any): boolean Check that the value is an interval object.
+---@field tuple fun(arg: any): boolean Check that the value is a tuple.
+---@field uint64 fun(arg: any): boolean Check that the value is a uint64 value.
+---@field uuid fun(arg: any): boolean Check that the value is a uuid object.
+---@field uuid_bin fun(arg: any): boolean Check that the value is a uuid as a 16-byte binary string.
+---@field uuid_str fun(arg: any): boolean Check that the value is a uuid as a 36-byte hexadecimal string.
 local checkers = rawget(_G, 'checkers') or {}
 rawset(_G, 'checkers', checkers)
 
+---When set to `true`, substitutes `nil` table arguments with empty tables for
+---backward compatibility with v2.1.
+---@type boolean
 local _checks_v2_compatible = rawget(_G, '_checks_v2_compatible') or false
 rawset(_G, '_checks_v2_compatible', _checks_v2_compatible)
 
 local ffi = require('ffi')
+
+---Check whether the specified value is a `uint64` value: an integer Lua number
+---in the range from 0 to 2^53-1 (inclusive), a cdata `ctype<uint64_t>`, or a
+---cdata `ctype<int64_t>` in the range from 0 to `LLONG_MAX`.
+---
+---@param arg any The value to check.
+---@return boolean `true` if the value is a `uint64` value, `false` otherwise.
 function checkers.uint64(arg)
     if type(arg) == 'number' then
         -- Double floating point format has 52 fraction bits
@@ -277,6 +344,13 @@ function checkers.uint64(arg)
     return false
 end
 
+---Check whether the specified value is an `int64` value: an integer Lua
+---number in the range from -2^53+1 to 2^53-1 (inclusive), a cdata
+---`ctype<int64_t>`, or a cdata `ctype<uint64_t>` in the range from 0 to
+---`LLONG_MAX`.
+---
+---@param arg any The value to check.
+---@return boolean `true` if the value is an `int64` value, `false` otherwise.
 function checkers.int64(arg)
     if type(arg) == 'number' then
         return (arg > -2^53) and (arg < 2^53) and (math.floor(arg) == arg)
@@ -293,6 +367,7 @@ function checkers.int64(arg)
     return false
 end
 
+---Check whether the specified value is a tuple.
 local has_box = rawget(_G, 'box') ~= nil
 if has_box and box.tuple ~= nil then
     checkers.tuple = box.tuple.is
@@ -303,11 +378,19 @@ if has_decimal then
     -- There is a decimal.is_decimal check since 2.4, but we
     -- reimplement it here to support older versions which have decimal.
     local cdata_t = ffi.typeof(decimal.new(0))
+    ---Check whether the specified value has the decimal type.
+    ---
+    ---@param arg any The value to check.
+    ---@return boolean `true` if the value has the decimal type, `false` otherwise.
     checkers.decimal = function(arg)
         return ffi.istype(cdata_t, arg)
     end
 end
 
+---Register a checker for a cdata type checked via FFI.
+---
+---@param checks_type string The name of the checker to register in `checkers`.
+---@param c_type string The C type name, e.g. `'struct tt_uuid'`.
 local function add_ffi_type_checker(checks_type, c_type)
     local has_cdata_t, cdata_t = pcall(ffi.typeof, c_type)
     if has_cdata_t then
@@ -322,6 +405,11 @@ end
 -- https://github.com/tarantool/tarantool/blob/7682d34162be34648172d91008e9185301bce8f6/src/lua/uuid.lua#L29
 add_ffi_type_checker('uuid', 'struct tt_uuid')
 
+---Check whether the specified value is a uuid represented by a 36-byte
+---hexadecimal string.
+---
+---@param arg any The value to check.
+---@return boolean `true` if the value is a uuid string, `false` otherwise.
 function checkers.uuid_str(arg)
     if type(arg) == 'string' and #arg == 36 then
         local match = arg:match(
@@ -339,6 +427,11 @@ function checkers.uuid_str(arg)
     end
 end
 
+---Check whether the specified value is a uuid represented by a 16-byte binary
+---string.
+---
+---@param arg any The value to check.
+---@return boolean `true` if the value is a uuid binary string, `false` otherwise.
 function checkers.uuid_bin(arg)
     if type(arg) == 'string' and #arg == 16 then
         return true
@@ -349,6 +442,7 @@ end
 
 add_ffi_type_checker('error', 'struct error')
 
+---Check whether the specified value is a datetime object.
 local has_datetime, datetime = pcall(require, 'datetime')
 if has_datetime then
     checkers.datetime = datetime.is_datetime
@@ -356,6 +450,7 @@ end
 
 add_ffi_type_checker('interval', 'struct interval')
 
+---@type checks
 return setmetatable(
     {
         checks = checks,

From 4cbbc929a3e619b4ac4629be4be3970cdd983ec2 Mon Sep 17 00:00:00 2001
From: Sergey Bronnikov <sergeyb@tarantool.org>
Date: Fri, 7 Aug 2026 12:54:11 +0300
Subject: [PATCH 07/14] emmyrc: initial config

The patch introduces an initial configuration file .emmyrc for
emmylua_check, it is a modern static analuzer for Lua.
The configuration file has the same excluded directories as in
.luacheckrc and config disables a number of rules. Most of them
will be enabled back in the following commits except the following
rules:
- "unresolved-require" (7 warnings) is disabled because most modules
  are Tarantool builtins: `json`, `log`, `uuid`; no source code is
  included in the project.
- "need-check-nil" (22 warnings) is disabled because these
  warnings are not critical and I don't want to add extra checks
  to the code.
- "redefined-local" is disabled because it was disabled for
  luacheck in the commit 49fa005dab08a1b206771e89e5231f779cccf914
  ("test: add linting stage").
---
 .emmyrc.json | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)
 create mode 100644 .emmyrc.json

diff --git a/.emmyrc.json b/.emmyrc.json
new file mode 100644
index 0000000..b5b80ab
--- /dev/null
+++ b/.emmyrc.json
@@ -0,0 +1,30 @@
+{
+  "$schema": "https://raw.githubusercontent.com/EmmyLuaLs/emmylua-analyzer-rust/refs/heads/main/crates/emmylua_code_analysis/resources/schema.json",
+  "workspace": {
+    "ignoreDir": [
+      ".rocks",
+      "build",
+      "tmp"
+    ]
+  },
+  "runtime": {
+    "version": "LuaJIT"
+  },
+  "diagnostics": {
+    "disable": [
+      "assign-type-mismatch",
+      "call-non-callable",
+      "duplicate-require",
+      "need-check-nil",
+      "param-type-mismatch",
+      "redefined-local",
+      "undefined-field",
+      "unnecessary-if",
+      "unresolved-require",
+      "unused"
+    ],
+    "globals": [
+      "box"
+    ]
+  }
+}

From 3430a0b462c09a32ced42ae25b3adc096a597fe8 Mon Sep 17 00:00:00 2001
From: Sergey Bronnikov <sergeyb@tarantool.org>
Date: Fri, 7 Aug 2026 13:22:43 +0300
Subject: [PATCH 08/14] emmyrc: fix assign-type-mismatch

The patch rule `assign-type-mismatch` in the .emmyrc and fixes
three warnings:

- @class checks moved to the module table - no longer sticks to
  local ffi.
- `checks(...)`: vararg typed as `checks.qualifier|number`, level
  annotated with ---@type number, stack level retrieved via
  narrowed local first.
- @field checks field consistent with type
  `fun(...: checks.qualifier|number)`.
---
 .emmyrc.json |  1 -
 checks.lua   | 21 ++++++++++++---------
 2 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/.emmyrc.json b/.emmyrc.json
index b5b80ab..435cd6d 100644
--- a/.emmyrc.json
+++ b/.emmyrc.json
@@ -12,7 +12,6 @@
   },
   "diagnostics": {
     "disable": [
-      "assign-type-mismatch",
       "call-non-callable",
       "duplicate-require",
       "need-check-nil",
diff --git a/checks.lua b/checks.lua
index 434e1e4..f4d07ff 100644
--- a/checks.lua
+++ b/checks.lua
@@ -6,10 +6,6 @@
 ---`checks.checks(type_1, ...)`.
 ---
 ---@alias checks.qualifier string|table<any, checks.qualifier>
----
----@class checks
----@field checks fun(...: checks.qualifier) Checks the arguments of the calling function.
----@field _VERSION string The module version.
 local ffi = require('ffi')
 
 ffi.cdef[[
@@ -227,13 +223,16 @@ end
 ---made optional (`'?string'`). Table qualifiers validate the values of a table
 ---argument.
 ---
----@param ... checks.qualifier Type qualifiers, one per argument to check.
+---@param ... checks.qualifier|number Type qualifiers, one per argument to
+---    check. The first argument may also be a stack level (used internally).
 local function checks(...)
     local skip = 0
 
+    ---@type number
     local level = 1
-    if type(...) == 'number' then
-        level = ...
+    local first = ...
+    if type(first) == 'number' then
+        level = first
         skip = 1
     end
     level = level + 1 -- escape the checks level
@@ -450,8 +449,10 @@ end
 
 add_ffi_type_checker('interval', 'struct interval')
 
----@type checks
-return setmetatable(
+---@class checks
+---@field checks fun(...: checks.qualifier|number) Checks the arguments of the calling function.
+---@field _VERSION string The module version.
+local M = setmetatable(
     {
         checks = checks,
         _VERSION = require('checks.version'),
@@ -463,3 +464,5 @@ return setmetatable(
         end
     }
 )
+
+return M

From 39f6abaccb0f5a5de22ad42f2ead5e11f8a4ffa6 Mon Sep 17 00:00:00 2001
From: Sergey Bronnikov <sergeyb@tarantool.org>
Date: Fri, 7 Aug 2026 13:55:31 +0300
Subject: [PATCH 09/14] emmyrc: fix call-non-callable

The patch enables rule `call-non-callable` and fixes warnings
produced by this rule: removed class checks/@field from the modul
table, now the `require('checks')` type is inferred from
setmetatable (callable via variadic `__call`, checks/_VERSION
fields are referenced). Field documentation has been moved to the
module header.
---
 .emmyrc.json | 1 -
 checks.lua   | 8 +++-----
 2 files changed, 3 insertions(+), 6 deletions(-)

diff --git a/.emmyrc.json b/.emmyrc.json
index 435cd6d..36de642 100644
--- a/.emmyrc.json
+++ b/.emmyrc.json
@@ -12,7 +12,6 @@
   },
   "diagnostics": {
     "disable": [
-      "call-non-callable",
       "duplicate-require",
       "need-check-nil",
       "param-type-mismatch",
diff --git a/checks.lua b/checks.lua
index f4d07ff..31fd1c8 100644
--- a/checks.lua
+++ b/checks.lua
@@ -2,8 +2,9 @@
 ---passed to a Lua function. It is designed to reveal mistakes in code, not to
 ---validate user input.
 ---
----The module table itself is callable: `checks(type_1, ...)` is equivalent to
----`checks.checks(type_1, ...)`.
+---The returned module table is callable: `checks(type_1, ...)` is equivalent
+---to `checks.checks(type_1, ...)`. It exposes the `checks` function and the
+---`_VERSION` string field.
 ---
 ---@alias checks.qualifier string|table<any, checks.qualifier>
 local ffi = require('ffi')
@@ -449,9 +450,6 @@ end
 
 add_ffi_type_checker('interval', 'struct interval')
 
----@class checks
----@field checks fun(...: checks.qualifier|number) Checks the arguments of the calling function.
----@field _VERSION string The module version.
 local M = setmetatable(
     {
         checks = checks,

From 6f0eb99da4bc76984cd4074e89165eba77c8736d Mon Sep 17 00:00:00 2001
From: Sergey Bronnikov <sergeyb@tarantool.org>
Date: Fri, 7 Aug 2026 13:59:04 +0300
Subject: [PATCH 10/14] emmyrc: fix duplicate-require

The patch enables rule `duplicate-require` in the .emmyrc
and removes duplicate require for `ffi` module.
---
 .emmyrc.json | 1 -
 checks.lua   | 2 --
 2 files changed, 3 deletions(-)

diff --git a/.emmyrc.json b/.emmyrc.json
index 36de642..9ae76a2 100644
--- a/.emmyrc.json
+++ b/.emmyrc.json
@@ -12,7 +12,6 @@
   },
   "diagnostics": {
     "disable": [
-      "duplicate-require",
       "need-check-nil",
       "param-type-mismatch",
       "redefined-local",
diff --git a/checks.lua b/checks.lua
index 31fd1c8..758cb04 100644
--- a/checks.lua
+++ b/checks.lua
@@ -317,8 +317,6 @@ rawset(_G, 'checkers', checkers)
 local _checks_v2_compatible = rawget(_G, '_checks_v2_compatible') or false
 rawset(_G, '_checks_v2_compatible', _checks_v2_compatible)
 
-local ffi = require('ffi')
-
 ---Check whether the specified value is a `uint64` value: an integer Lua number
 ---in the range from 0 to 2^53-1 (inclusive), a cdata `ctype<uint64_t>`, or a
 ---cdata `ctype<int64_t>` in the range from 0 to `LLONG_MAX`.

From 0e222a1e1e51eca7c957d3d3c6ad39453036f0e0 Mon Sep 17 00:00:00 2001
From: Sergey Bronnikov <sergeyb@tarantool.org>
Date: Fri, 7 Aug 2026 14:48:33 +0300
Subject: [PATCH 11/14] emmyrc: fix param-type-mismatch

The patch enables rule `param-type-mismatch` in the .emmyrc
and fixes 20 warnings produced by this rule.
---
 .emmyrc.json  |  1 -
 checks.lua    | 12 +++++++++++-
 test/test.lua |  2 ++
 3 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/.emmyrc.json b/.emmyrc.json
index 9ae76a2..8553638 100644
--- a/.emmyrc.json
+++ b/.emmyrc.json
@@ -13,7 +13,6 @@
   "diagnostics": {
     "disable": [
       "need-check-nil",
-      "param-type-mismatch",
       "redefined-local",
       "undefined-field",
       "unnecessary-if",
diff --git a/checks.lua b/checks.lua
index 758cb04..f1e2a44 100644
--- a/checks.lua
+++ b/checks.lua
@@ -171,11 +171,13 @@ local function check_table_type(tbl, expected_fields)
         if type(expected_type) == 'string' then
             local ok, efmt = check_string_type(value, expected_type)
             if not ok then
+                ---@cast efmt string
                 return nil, string.format(efmt, '%s'..keyname_fmt(expected_key), '%s')
             end
         elseif type(expected_type) == 'table' then
             local ok, efmt = check_string_type(value, '?table')
             if not ok then
+                ---@cast efmt string
                 return nil, string.format(efmt, '%s'..keyname_fmt(expected_key), '%s')
             end
 
@@ -186,6 +188,7 @@ local function check_table_type(tbl, expected_fields)
 
             local ok, efmt = check_table_type(value, expected_type)
             if not ok then
+                ---@cast efmt string
                 return nil, string.format(efmt, '%s'..keyname_fmt(expected_key), '%s')
             end
         else
@@ -229,10 +232,11 @@ end
 local function checks(...)
     local skip = 0
 
-    ---@type number
+    ---@type integer
     local level = 1
     local first = ...
     if type(first) == 'number' then
+        ---@cast first integer
         level = first
         skip = 1
     end
@@ -257,6 +261,7 @@ local function checks(...)
             local ok, efmt = check_string_type(value, expected_type)
             if not ok then
                 local info = debug.getinfo(level, 'nl')
+                ---@cast efmt string
                 local err = string.format(efmt, '#'..tostring(i), info.name)
                 error(err, level)
             end
@@ -265,18 +270,23 @@ local function checks(...)
             local ok, efmt = check_string_type(value, '?table')
             if not ok then
                 local info = debug.getinfo(level, 'nl')
+                ---@cast efmt string
                 local err = string.format(efmt, '#'..tostring(i), info.name)
                 error(err, level)
             end
 
             if rawget(_G, '_checks_v2_compatible') and value == nil then
                 value = {}
+                -- In emmylua-check 0.22.0 the debug.setlocal index
+                -- parameter is mistyped as `string`; it is an integer.
+                ---@diagnostic disable-next-line: param-type-mismatch
                 debug.setlocal(level, i, value)
             end
 
             local ok, efmt = check_table_type(value, expected_type)
             if not ok then
                 local info = debug.getinfo(level, 'nl')
+                ---@cast efmt string
                 local err = string.format(efmt, argname, info.name)
                 error(err, level)
             end
diff --git a/test/test.lua b/test/test.lua
index 1f55aa3..89ae5db 100755
--- a/test/test.lua
+++ b/test/test.lua
@@ -456,6 +456,7 @@ for _, case in pairs(err_cases) do
 
     g[name] = function(_)
         local fn = loadstring(case.code)
+        ---@cast fn function
         local ok, err = pcall(fn)
 
         if case.error == nil then
@@ -1095,6 +1096,7 @@ for _, case in pairs(ret_cases) do
         t.skip_if(case.skip, "type unsupported")
 
         local fn = loadstring(case.code)
+        ---@cast fn function
         local ok, err = pcall(fn)
         t.assert_equals(case.ok, ok, err)
     end

From 9c6a3682d77e957a69c244946e89d9cb50ed1cbb Mon Sep 17 00:00:00 2001
From: Sergey Bronnikov <sergeyb@tarantool.org>
Date: Fri, 7 Aug 2026 15:04:29 +0300
Subject: [PATCH 12/14] emmyrc: fix undefined-field

The patch enables rule `undefined-field` in the .emmyrc and fixes
errors produced by this rule. The error is in using `table.deepcopy()`
in test/test.lua because Tarantool API is unknown to the analyzer.
The patch created a definition for `table.deepcopy()` in a file
test/types.lua.
---
 .emmyrc.json   | 1 -
 test/types.lua | 6 ++++++
 2 files changed, 6 insertions(+), 1 deletion(-)
 create mode 100644 test/types.lua

diff --git a/.emmyrc.json b/.emmyrc.json
index 8553638..089c271 100644
--- a/.emmyrc.json
+++ b/.emmyrc.json
@@ -14,7 +14,6 @@
     "disable": [
       "need-check-nil",
       "redefined-local",
-      "undefined-field",
       "unnecessary-if",
       "unresolved-require",
       "unused"
diff --git a/test/types.lua b/test/types.lua
new file mode 100644
index 0000000..07e6b2b
--- /dev/null
+++ b/test/types.lua
@@ -0,0 +1,6 @@
+---@meta
+---
+--- Tarantool extensions to the standard Lua `table` library.
+---
+---@class tablelib
+---@field deepcopy fun(t: table): table Deep-copies a table.

From 6151c8dff419961ecbdba1e1279dfdc0eb77742b Mon Sep 17 00:00:00 2001
From: Sergey Bronnikov <sergeyb@tarantool.org>
Date: Fri, 7 Aug 2026 15:13:37 +0300
Subject: [PATCH 13/14] emmyrc: fix unnecessary-if

The patch enables `unnecessary-if` in the .emmyrc and fixes
a warning produced by this rule. The reason of warning is an
unknown type of variable `qualifier`. The analyzer infers the
`optional` field as literal `false` and doesn't track the assignment
`qualifier.optional = true` inside the `gmatch` loop, so
`unnecessary-if` considers the condition is always `false`. This
is a false positive - at runtime, the condition is reachable
(e.g., '?string').

The patch adds the annotation to the local variable `qualifier` -
the `optional` field is now typed as boolean, and the analyzer
no longer considers the condition to always be false.
---
 .emmyrc.json | 1 -
 checks.lua   | 1 +
 2 files changed, 1 insertion(+), 1 deletion(-)

diff --git a/.emmyrc.json b/.emmyrc.json
index 089c271..c418dba 100644
--- a/.emmyrc.json
+++ b/.emmyrc.json
@@ -14,7 +14,6 @@
     "disable": [
       "need-check-nil",
       "redefined-local",
-      "unnecessary-if",
       "unresolved-require",
       "unused"
     ],
diff --git a/checks.lua b/checks.lua
index f1e2a44..c61997b 100644
--- a/checks.lua
+++ b/checks.lua
@@ -92,6 +92,7 @@ local function check_string_type(value, expected_type)
     end
 
     -- 2. Parse type qualifier
+    ---@type { [integer]: string, optional: boolean }?
     local qualifier = _qualifiers_cache[expected_type]
     if qualifier == nil then
         qualifier = { optional = false }

From 35ed1d97294e81fca8e36fcbfea9d31eaabda4ac Mon Sep 17 00:00:00 2001
From: Sergey Bronnikov <sergeyb@tarantool.org>
Date: Fri, 7 Aug 2026 16:17:13 +0300
Subject: [PATCH 14/14] emmyrc: fix unused

The patch enables rule `unused` and fixes a warnings produced by
this rule by adding an underscore to the prefix of variables that
are not used.
---
 .emmyrc.json      |  3 +-
 test/perftest.lua |  2 +-
 test/test.lua     | 84 +++++++++++++++++++++++------------------------
 3 files changed, 44 insertions(+), 45 deletions(-)

diff --git a/.emmyrc.json b/.emmyrc.json
index c418dba..0e12414 100644
--- a/.emmyrc.json
+++ b/.emmyrc.json
@@ -14,8 +14,7 @@
     "disable": [
       "need-check-nil",
       "redefined-local",
-      "unresolved-require",
-      "unused"
+      "unresolved-require"
     ],
     "globals": [
       "box"
diff --git a/test/perftest.lua b/test/perftest.lua
index 13502e7..1a83176 100755
--- a/test/perftest.lua
+++ b/test/perftest.lua
@@ -134,7 +134,7 @@ for _, case in pairs(cases) do
     local name = ('test_%s_%s'):format(json.encode(case.check), case.argtype):gsub('%.', '_')
 
     g[name] = function(_)
-        local fn = function(arg) -- luacheck: no unused args
+        local fn = function(_arg)
             checks(case.check)
         end
 
diff --git a/test/test.lua b/test/test.lua
index 89ae5db..652d5b6 100755
--- a/test/test.lua
+++ b/test/test.lua
@@ -19,41 +19,41 @@ end
 local testdata = {}
 
 local _l_number_optstring = 2 + debug.getinfo(1).currentline
-function testdata.fn_number_optstring(arg1, arg2) -- luacheck: no unused args
+function testdata.fn_number_optstring(_arg1, _arg2)
     checks('number', '?string')
 end
 
 local _l_number_or_string = 2 + debug.getinfo(1).currentline
-function testdata.fn_number_or_string(arg1) -- luacheck: no unused args
+function testdata.fn_number_or_string(_arg1)
     checks('number|string')
 end
 
 local _l_positive_number = 2 + debug.getinfo(1).currentline
-function testdata.fn_positive_number(arg1) -- luacheck: no unused args
+function testdata.fn_positive_number(_arg1)
     checks('positive_number')
 end
 
-function testdata.fn_anytype(arg1) -- luacheck: no unused args
+function testdata.fn_anytype(_arg1)
     checks('?')
 end
 
 local _l_nil_or_number_or_string = 2 + debug.getinfo(1).currentline
-function testdata.fn_nil_or_number_or_string(arg1) -- luacheck: no unused args
+function testdata.fn_nil_or_number_or_string(_arg1)
     checks('nil|number|string')
 end
 
 local _l_optnumber_or_optstring = 2 + debug.getinfo(1).currentline
-function testdata.fn_optnumber_or_optstring(arg1) -- luacheck: no unused args
+function testdata.fn_optnumber_or_optstring(_arg1)
     checks('?number|?string')
 end
 
 local _l_varargs = 2 + debug.getinfo(1).currentline
-function testdata.fn_varargs(arg1, ...) -- luacheck: no unused args
+function testdata.fn_varargs(_arg1, ...) -- luacheck: ignore 212
     checks('string')
 end
 
 local _l_options = 2 + debug.getinfo(1).currentline
-function testdata.fn_options(options) -- luacheck: no unused args
+function testdata.fn_options(_options)
     checks({
         mystring = '?string',
         mynumber = '?number',
@@ -61,17 +61,17 @@ function testdata.fn_options(options) -- luacheck: no unused args
 end
 
 local _l_array = 2 + debug.getinfo(1).currentline
-function testdata.fn_array(array) -- luacheck: no unused args
+function testdata.fn_array(_array)
     checks({'number', 'number'})
 end
 
 local _l_table = 2 + debug.getinfo(1).currentline
-function testdata.fn_table(table) -- luacheck: no unused args
+function testdata.fn_table(_table)
     checks({mykey = 'number'})
 end
 
 local _l_inception = 2 + debug.getinfo(1).currentline
-function testdata.fn_inception(options) -- luacheck: no unused args
+function testdata.fn_inception(_options)
     checks({
         we = {
             need = {
@@ -90,27 +90,27 @@ local function deepchecks()
 end
 
 local _l_deepcheck = 2 + debug.getinfo(1).currentline
-function testdata.fn_deepcheck(arg1) -- luacheck: no unused args
+function testdata.fn_deepcheck(_arg1)
     deepchecks()
 end
 
 local _l_excess_checks = 2 + debug.getinfo(1).currentline
-function testdata.fn_excess_checks(arg1) -- luacheck: no unused args
+function testdata.fn_excess_checks(_arg1)
     checks('?number', '?string')
 end
 
 local _l_missing_checks = 2 + debug.getinfo(1).currentline
-function testdata.fn_missing_checks(arg1, arg2) -- luacheck: no unused args
+function testdata.fn_missing_checks(_arg1, _arg2)
     checks('?number')
 end
 
 local _l_bad_check_type_1 = 2 + debug.getinfo(1).currentline
-function testdata.bad_check_type_1(arg1, arg2) -- luacheck: no unused args
+function testdata.bad_check_type_1(_arg1, _arg2)
     checks("?string", 5)
 end
 
 local _l_bad_check_type_2 = 2 + debug.getinfo(1).currentline
-function testdata.bad_check_type_2(arg1, arg2) -- luacheck: no unused args
+function testdata.bad_check_type_2(_arg1, _arg2)
     checks({param = 5})
 end
 
@@ -294,12 +294,12 @@ local err_cases = {
     {
         code = 'fn_options({mynumber = "bad"})',
         line = _l_options,
-        error = 'bad argument options.mynumber to fn_options (?number expected, got string)',
+        error = 'bad argument _options.mynumber to fn_options (?number expected, got string)',
     },
     {
         code = 'fn_options({badfield = "bad"})',
         line = _l_options,
-        error = 'unexpected argument options.badfield to fn_options',
+        error = 'unexpected argument _options.badfield to fn_options',
     },
 
     -- fn_array
@@ -311,32 +311,32 @@ local err_cases = {
     {
         code = 'fn_array()',
         line = _l_array,
-        error = 'bad argument array[1] to fn_array (number expected, got nil)',
+        error = 'bad argument _array[1] to fn_array (number expected, got nil)',
     },
     {
         code = 'fn_array(nil)',
         line = _l_array,
-        error = 'bad argument array[1] to fn_array (number expected, got nil)',
+        error = 'bad argument _array[1] to fn_array (number expected, got nil)',
     },
     {
         code = 'fn_array(box.NULL)',
         line = _l_array,
-        error = 'bad argument array[1] to fn_array (number expected, got nil)',
+        error = 'bad argument _array[1] to fn_array (number expected, got nil)',
     },
     {
         code = 'fn_array({})',
         line = _l_array,
-        error = 'bad argument array[1] to fn_array (number expected, got nil)',
+        error = 'bad argument _array[1] to fn_array (number expected, got nil)',
     },
     {
         code = 'fn_array({"str1"})',
         line = _l_array,
-        error = 'bad argument array[1] to fn_array (number expected, got string)',
+        error = 'bad argument _array[1] to fn_array (number expected, got string)',
     },
     {
         code = 'fn_array({1})',
         line = _l_array,
-        error = 'bad argument array[2] to fn_array (number expected, got nil)',
+        error = 'bad argument _array[2] to fn_array (number expected, got nil)',
     },
     {
         code = 'fn_array({1, 2})',
@@ -344,7 +344,7 @@ local err_cases = {
     {
         code = 'fn_array({1, 2, 3})',
         line = _l_array,
-        error = 'unexpected argument array[3] to fn_array',
+        error = 'unexpected argument _array[3] to fn_array',
     },
 
     -- fn_table
@@ -356,17 +356,17 @@ local err_cases = {
     {
         code = 'fn_table()',
         line = _l_table,
-        error = 'bad argument table.mykey to fn_table (number expected, got nil)',
+        error = 'bad argument _table.mykey to fn_table (number expected, got nil)',
     },
     {
         code = 'fn_table({})',
         line = _l_table,
-        error = 'bad argument table.mykey to fn_table (number expected, got nil)',
+        error = 'bad argument _table.mykey to fn_table (number expected, got nil)',
     },
     {
         code = 'fn_table({mykey = "str"})',
         line = _l_table,
-        error = 'bad argument table.mykey to fn_table (number expected, got string)',
+        error = 'bad argument _table.mykey to fn_table (number expected, got string)',
     },
     {
         code = 'fn_table({mykey = 0})',
@@ -374,7 +374,7 @@ local err_cases = {
     {
         code = 'fn_table({mykey = 0, excess = 1})',
         line = _l_table,
-        error = 'unexpected argument table.excess to fn_table',
+        error = 'unexpected argument _table.excess to fn_table',
     },
 
     -- fn_inception
@@ -387,7 +387,7 @@ local err_cases = {
     {
         code = 'fn_inception({we = false})',
         line = _l_inception,
-        error = 'bad argument options.we to fn_inception (?table expected, got boolean)',
+        error = 'bad argument _options.we to fn_inception (?table expected, got boolean)',
     },
     {
         code = 'fn_inception({we = {}})',
@@ -407,7 +407,7 @@ local err_cases = {
     {
         code = 'fn_inception({we = {need = {to = {go = {deeper = {}}}}}})',
         line = _l_inception,
-        error = 'bad argument options.we.need.to.go.deeper to fn_inception (?number expected, got table)',
+        error = 'bad argument _options.we.need.to.go.deeper to fn_inception (?number expected, got table)',
     },
 
     -- fn_deepcheck
@@ -429,7 +429,7 @@ local err_cases = {
     {
         code = 'fn_missing_checks()',
         line = _l_missing_checks,
-        error = 'checks: argument "arg2" is not checked',
+        error = 'checks: argument "_arg2" is not checked',
     },
     {
         code = 'bad_check_type_1()',
@@ -583,34 +583,34 @@ for _, case in pairs(options_v2_cases) do
 end
 
 ------------------------------------------------------------------------------
-function testdata.fn_int64(arg) -- luacheck: no unused args
+function testdata.fn_int64(_arg)
     checks('int64')
 end
 
-function testdata.fn_uint64(arg) -- luacheck: no unused args
+function testdata.fn_uint64(_arg)
     checks('uint64')
 end
 
 local uuid = require('uuid')
 testdata.myid = uuid()
 
-function testdata.fn_uuid(arg) -- luacheck: no unused args
+function testdata.fn_uuid(_arg)
     checks('uuid')
 end
 
-function testdata.fn_uuid_str(arg) -- luacheck: no unused args
+function testdata.fn_uuid_str(_arg)
     checks('uuid_str')
 end
 
-function testdata.fn_uuid_bin(arg) -- luacheck: no unused args
+function testdata.fn_uuid_bin(_arg)
     checks('uuid_bin')
 end
 
-function testdata.fn_tuple(arg) -- luacheck: no unused args
+function testdata.fn_tuple(_arg)
     checks('tuple')
 end
 
-function testdata.fn_decimal(arg) -- luacheck: no unused args
+function testdata.fn_decimal(_arg)
     checks('decimal')
 end
 
@@ -619,13 +619,13 @@ if has_decimal then
     testdata.decimal = decimal
 end
 
-function testdata.fn_error(arg) -- luacheck: no unused args
+function testdata.fn_error(_arg)
     checks('error')
 end
 
 local has_error = (box.error ~= nil) and (box.error.new ~= nil)
 
-function testdata.fn_datetime(arg) -- luacheck: no unused args
+function testdata.fn_datetime(_arg)
     checks('datetime')
 end
 
@@ -634,7 +634,7 @@ if has_datetime then
     testdata.datetime = datetime
 end
 
-function testdata.fn_interval(arg) -- luacheck: no unused args
+function testdata.fn_interval(_arg)
     checks('interval')
 end