diff --git a/.editorconfig b/.editorconfig
new file mode 100644
index 0000000..5d66bc4
--- /dev/null
+++ b/.editorconfig
@@ -0,0 +1,27 @@
+root = true
+
+[*]
+end_of_line = lf
+insert_final_newline = true
+charset = utf-8
+trim_trailing_whitespace = true
+
+[*.{php,phpt}]
+indent_style = tab
+indent_size = 4
+
+[*.xml]
+indent_style = tab
+indent_size = 4
+
+[*.neon]
+indent_style = tab
+indent_size = 4
+
+[*.{yaml,yml}]
+indent_style = space
+indent_size = 2
+
+[composer.json]
+indent_style = tab
+indent_size = 4
diff --git a/.gitattributes b/.gitattributes
new file mode 100644
index 0000000..45a67c4
--- /dev/null
+++ b/.gitattributes
@@ -0,0 +1,10 @@
+*.php text eol=lf
+
+.github export-ignore
+tests export-ignore
+tmp export-ignore
+.gitattributes export-ignore
+.gitignore export-ignore
+Makefile export-ignore
+phpstan.neon export-ignore
+phpunit.xml export-ignore
diff --git a/.github/renovate.json b/.github/renovate.json
new file mode 100644
index 0000000..d3f5961
--- /dev/null
+++ b/.github/renovate.json
@@ -0,0 +1,19 @@
+{
+  "extends": [
+    "config:base",
+    "schedule:weekly"
+  ],
+  "rangeStrategy": "update-lockfile",
+  "packageRules": [
+    {
+      "matchPaths": ["+(composer.json)"],
+      "enabled": true,
+      "groupName": "root-composer"
+    },
+    {
+      "matchPaths": [".github/**"],
+      "enabled": true,
+      "groupName": "github-actions"
+    }
+  ]
+}
diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
new file mode 100644
index 0000000..2624592
--- /dev/null
+++ b/.github/workflows/build.yml
@@ -0,0 +1,149 @@
+# https://help.github.com/en/categories/automating-your-workflow-with-github-actions
+
+name: "Build"
+
+on:
+  pull_request:
+  push:
+    branches:
+      - "1.0.x"
+
+jobs:
+  lint:
+    name: "Lint"
+    runs-on: "ubuntu-latest"
+
+    strategy:
+      fail-fast: false
+      matrix:
+        php-version:
+          - "8.2"
+          - "8.3"
+          - "8.4"
+
+    steps:
+      - name: "Checkout"
+        uses: actions/checkout@v5
+
+      - name: "Install PHP"
+        uses: "shivammathur/setup-php@v2"
+        with:
+          coverage: "none"
+          php-version: "${{ matrix.php-version }}"
+          ini-file: development
+          extensions: "mongodb"
+
+      - name: "Validate Composer"
+        run: "composer validate"
+
+      - name: "Allow installing on PHP 8.4"
+        if: matrix.php-version == '8.4'
+        run: "composer config platform.php 8.3.99"
+
+      - name: "Install dependencies"
+        run: "composer install --no-interaction --no-progress"
+
+      - name: "Lint"
+        run: "make lint"
+
+  coding-standard:
+    name: "Coding Standard"
+
+    runs-on: "ubuntu-latest"
+
+    steps:
+      - name: "Checkout"
+        uses: actions/checkout@v5
+
+      - name: "Checkout build-cs"
+        uses: actions/checkout@v5
+        with:
+          repository: "phpstan/build-cs"
+          path: "build-cs"
+          ref: "2.x"
+
+      - name: "Install PHP"
+        uses: "shivammathur/setup-php@v2"
+        with:
+          coverage: "none"
+          php-version: "8.2"
+          ini-file: development
+
+      - name: "Validate Composer"
+        run: "composer validate"
+
+      - name: "Install dependencies"
+        run: "composer install --no-interaction --no-progress"
+
+      - name: "Install build-cs dependencies"
+        working-directory: "build-cs"
+        run: "composer install --no-interaction --no-progress"
+
+      - name: "Lint"
+        run: "make lint"
+
+      - name: "Coding Standard"
+        run: "make cs"
+
+  tests:
+    name: "Tests"
+    runs-on: "ubuntu-latest"
+
+    strategy:
+      fail-fast: false
+      matrix:
+        php-version:
+          - "8.2"
+          - "8.3"
+          - "8.4"
+
+    steps:
+      - name: "Checkout"
+        uses: actions/checkout@v5
+
+      - name: "Install PHP"
+        uses: "shivammathur/setup-php@v2"
+        with:
+          coverage: "xdebug"
+          php-version: "${{ matrix.php-version }}"
+          ini-file: development
+          extensions: "mongodb"
+
+      - name: "Allow installing on PHP 8.4"
+        if: matrix.php-version == '8.4'
+        run: "composer config platform.php 8.3.99"
+
+      - name: "Install dependencies"
+        run: "composer install --no-interaction --no-progress"
+
+      - name: "Tests"
+        run: "make tests"
+
+  static-analysis:
+    name: "PHPStan"
+    runs-on: "ubuntu-latest"
+
+    strategy:
+      fail-fast: false
+      matrix:
+        php-version:
+          - "8.2"
+          - "8.3"
+          - "8.4"
+
+    steps:
+      - name: "Checkout"
+        uses: actions/checkout@v5
+
+      - name: "Install PHP"
+        uses: "shivammathur/setup-php@v2"
+        with:
+          coverage: "none"
+          php-version: "${{ matrix.php-version }}"
+          ini-file: development
+
+      - name: "Install dependencies"
+        run: "composer install --no-interaction --no-progress"
+
+      - name: "PHPStan"
+        run: "make phpstan"
diff --git a/.github/workflows/create-tag.yml b/.github/workflows/create-tag.yml
new file mode 100644
index 0000000..fd91816
--- /dev/null
+++ b/.github/workflows/create-tag.yml
@@ -0,0 +1,53 @@
+# https://help.github.com/en/categories/automating-your-workflow-with-github-actions
+
+name: "Create tag"
+
+on:
+  # https://docs.github.com/en/actions/using-workflows/events-that-trigger-workflows#workflow_dispatch
+  workflow_dispatch:
+    inputs:
+      version:
+        description: 'Next version'
+        required: true
+        default: 'patch'
+        type: choice
+        options:
+          - patch
+          - minor
+
+jobs:
+  create-tag:
+    name: "Create tag"
+    runs-on: "ubuntu-latest"
+    steps:
+      - name: "Checkout"
+        uses: actions/checkout@v5
+        with:
+          fetch-depth: 0
+          token: ${{ secrets.PHPSTAN_BOT_TOKEN }}
+
+      - name: 'Get Previous tag'
+        id: previoustag
+        uses: "WyriHaximus/github-action-get-previous-tag@v1"
+        env:
+          GITHUB_TOKEN: "${{ secrets.GITHUB_TOKEN }}"
+
+      - name: 'Get next versions'
+        id: semvers
+        uses: "WyriHaximus/github-action-next-semvers@v1"
+        with:
+          version: ${{ steps.previoustag.outputs.tag }}
+
+      - name: "Create new minor tag"
+        uses: rickstaa/action-create-tag@v1
+        if: inputs.version == 'minor'
+        with:
+          tag: ${{ steps.semvers.outputs.minor }}
+          message: ${{ steps.semvers.outputs.minor }}
+
+      - name: "Create new patch tag"
+        uses: rickstaa/action-create-tag@v1
+        if: inputs.version == 'patch'
+        with:
+          tag: ${{ steps.semvers.outputs.patch }}
+          message: ${{ steps.semvers.outputs.patch }}
diff --git a/.github/workflows/release-toot.yml b/.github/workflows/release-toot.yml
new file mode 100644
index 0000000..1ba4fd7
--- /dev/null
+++ b/.github/workflows/release-toot.yml
@@ -0,0 +1,21 @@
+name: Toot release
+
+# More triggers
+# https://docs.github.com/en/actions/learn-github-actions/events-that-trigger-workflows#release
+on:
+  release:
+    types: [published]
+
+jobs:
+  toot:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: cbrgm/mastodon-github-action@v2
+        if: ${{ !github.event.repository.private }}
+        with:
+          # GitHub event payload
+          # https://docs.github.com/en/developers/webhooks-and-events/webhooks/webhook-events-and-payloads#release
+          message: "New release: ${{ github.event.repository.name }} ${{ github.event.release.tag_name }} ${{ github.event.release.html_url }} #phpstan"
+        env:
+          MASTODON_URL: https://phpc.social
+          MASTODON_ACCESS_TOKEN: ${{ secrets.MASTODON_ACCESS_TOKEN }}
diff --git a/.github/workflows/release-tweet.yml b/.github/workflows/release-tweet.yml
new file mode 100644
index 0000000..d81f34c
--- /dev/null
+++ b/.github/workflows/release-tweet.yml
@@ -0,0 +1,24 @@
+name: Tweet release
+
+# More triggers
+# https://docs.github.com/en/actions/learn-github-actions/events-that-trigger-workflows#release
+on:
+  release:
+    types: [published]
+
+jobs:
+  tweet:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: Eomm/why-don-t-you-tweet@v2
+        if: ${{ !github.event.repository.private }}
+        with:
+          # GitHub event payload
+          # https://docs.github.com/en/developers/webhooks-and-events/webhooks/webhook-events-and-payloads#release
+          tweet-message: "New release: ${{ github.event.repository.name }} ${{ github.event.release.tag_name }} ${{ github.event.release.html_url }} #phpstan"
+        env:
+          # Get your tokens from https://developer.twitter.com/apps
+          TWITTER_CONSUMER_API_KEY: ${{ secrets.TWITTER_CONSUMER_API_KEY }}
+          TWITTER_CONSUMER_API_SECRET: ${{ secrets.TWITTER_CONSUMER_API_SECRET }}
+          TWITTER_ACCESS_TOKEN: ${{ secrets.TWITTER_ACCESS_TOKEN }}
+          TWITTER_ACCESS_TOKEN_SECRET: ${{ secrets.TWITTER_ACCESS_TOKEN_SECRET }}
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
new file mode 100644
index 0000000..ed7e51a
--- /dev/null
+++ b/.github/workflows/release.yml
@@ -0,0 +1,33 @@
+# https://help.github.com/en/categories/automating-your-workflow-with-github-actions
+
+name: "Create release"
+
+on:
+  push:
+    tags:
+      - '*'
+
+jobs:
+  deploy:
+    name: "Deploy"
+    runs-on: "ubuntu-latest"
+
+    steps:
+      - name: "Checkout"
+        uses: actions/checkout@v5
+
+      - name: Generate changelog
+        id: changelog
+        uses: metcalfc/changelog-generator@v4.6.2
+        with:
+          myToken: ${{ secrets.PHPSTAN_BOT_TOKEN }}
+
+      - name: "Create release"
+        id: create-release
+        uses: actions/create-release@v1
+        env:
+          GITHUB_TOKEN: ${{ secrets.PHPSTAN_BOT_TOKEN }}
+        with:
+          tag_name: ${{ github.ref }}
+          release_name: ${{ github.ref }}
+          body: ${{ steps.changelog.outputs.changelog }}
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..e3d740a
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,6 @@
+/tests/tmp
+/build-cs
+/vendor
+/composer.lock
+/.env
+.phpunit.result.cache
diff --git a/LICENSE b/LICENSE
new file mode 100644
index 0000000..e5f34e6
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,22 @@
+MIT License
+
+Copyright (c) 2016 Ondřej Mirtes
+Copyright (c) 2025 PHPStan s.r.o.
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..8c11203
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,34 @@
+.PHONY: check
+check: lint cs tests phpstan
+
+.PHONY: tests
+tests:
+	php vendor/bin/phpunit
+
+.PHONY: lint
+lint:
+	php vendor/bin/parallel-lint --colors \
+		--exclude tests/Rules/DeadCode/data/bug-383.php \
+		src tests
+
+.PHONY: cs-install
+cs-install:
+	git clone https://github.com/phpstan/build-cs.git || true
+	git -C build-cs fetch origin && git -C build-cs reset --hard origin/2.x
+	composer install --working-dir build-cs
+
+.PHONY: cs
+cs:
+	php build-cs/vendor/bin/phpcs --standard=build-cs/phpcs.xml src tests
+
+.PHONY: cs-fix
+cs-fix:
+	php build-cs/vendor/bin/phpcbf --standard=build-cs/phpcs.xml src tests
+
+.PHONY: phpstan
+phpstan:
+	php vendor/bin/phpstan analyse -c phpstan.neon
+
+.PHONY: phpstan-generate-baseline
+phpstan-generate-baseline:
+	php vendor/bin/phpstan analyse -c phpstan.neon -b phpstan-baseline.neon
diff --git a/composer.json b/composer.json
new file mode 100644
index 0000000..b89d689
--- /dev/null
+++ b/composer.json
@@ -0,0 +1,37 @@
+{
+	"name": "phpstan/build-infection",
+	"description": "Infection extensions for PHPStan",
+	"license": [
+		"MIT"
+	],
+	"require": {
+		"php": "^7.4 || ^8.0",
+		"infection/infection": "^0.31.6"
+	},
+	"require-dev": {
+		"php-parallel-lint/php-parallel-lint": "^1.2",
+		"phpstan/phpstan": "^2.1.13",
+		"phpstan/phpstan-deprecation-rules": "^2.0.2",
+		"phpstan/phpstan-phpunit": "^2.0",
+		"phpstan/phpstan-strict-rules": "^2.0",
+		"phpunit/phpunit": "^11.5.23"
+	},
+	"config": {
+		"sort-packages": true,
+		"allow-plugins": {
+			"infection/extension-installer": true
+		}
+	},
+	"autoload": {
+		"psr-4": {
+			"PHPStan\\": "src/"
+		}
+	},
+	"autoload-dev": {
+		"classmap": [
+			"tests/"
+		]
+	},
+	"minimum-stability": "dev",
+	"prefer-stable": true
+}
diff --git a/infection.json5 b/infection.json5
new file mode 100644
index 0000000..7afd723
--- /dev/null
+++ b/infection.json5
@@ -0,0 +1,17 @@
+{
+  "$schema": "vendor/infection/infection/resources/schema.json",
+  "timeout": 30,
+  "source": {
+    "directories": [
+      "src"
+    ]
+  },
+  "staticAnalysisTool": "phpstan",
+  "logs": {
+    "text": "tmp/infection.log"
+  },
+  "mutators": {
+    "@default": false,
+    "PHPStan\\Infection\\TrinaryLogicMutator": true
+  }
+}
diff --git a/phpstan.neon b/phpstan.neon
new file mode 100644
index 0000000..6d7c0fd
--- /dev/null
+++ b/phpstan.neon
@@ -0,0 +1,7 @@
+parameters:
+	level: 8
+	paths:
+		- src
+		- tests
+
+	resultCachePath: tmp/resultCache.php
diff --git a/phpunit.xml b/phpunit.xml
new file mode 100644
index 0000000..4674938
--- /dev/null
+++ b/phpunit.xml
@@ -0,0 +1,19 @@
+<?xml version="1.0"?>
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         colors="true"
+		 bootstrap="./vendor/autoload.php"
+         beStrictAboutChangesToGlobalState="true"
+         beStrictAboutOutputDuringTests="true"
+         failOnRisky="true"
+         failOnWarning="true"
+         xsi:noNamespaceSchemaLocation="vendor/phpunit/phpunit/phpunit.xsd"
+         executionOrder="random"
+>
+    <testsuites>
+        <testsuite name="Infection for PHPStan">
+            <directory suffix="Test.php">tests</directory>
+        </testsuite>
+    </testsuites>
+
+    <logging/>
+</phpunit>
diff --git a/src/Infection/TrinaryLogicMutator.php b/src/Infection/TrinaryLogicMutator.php
new file mode 100644
index 0000000..eb527a2
--- /dev/null
+++ b/src/Infection/TrinaryLogicMutator.php
@@ -0,0 +1,69 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Infection;
+
+use Infection\Mutator\Definition;
+use Infection\Mutator\Mutator;
+use Infection\Mutator\MutatorCategory;
+use LogicException;
+use PhpParser\Node;
+use function in_array;
+
+/**
+ * @implements Mutator<Node\Expr\MethodCall>
+ */
+final class TrinaryLogicMutator implements Mutator
+{
+
+	public static function getDefinition(): Definition
+	{
+		return new Definition(
+			<<<'TXT'
+				Replaces TrinaryLogic->yes() with !TrinaryLogic->no() and vice versa.
+				TXT
+			,
+			MutatorCategory::ORTHOGONAL_REPLACEMENT,
+			null,
+			<<<'DIFF'
+				- $type->isBoolean()->yes();
+				+ !$type->isBoolean()->no();
+			DIFF,
+		);
+	}
+
+	public function getName(): string
+	{
+		return self::class;
+	}
+
+	public function canMutate(Node $node): bool
+	{
+		if (!$node instanceof Node\Expr\MethodCall) {
+			return false;
+		}
+
+		if (!$node->name instanceof Node\Identifier) {
+			return false;
+		}
+
+		if (!in_array($node->name->name, ['yes', 'no'], true)) {
+			return false;
+		}
+
+		return true;
+	}
+
+	public function mutate(Node $node): iterable
+	{
+		if (!$node->name instanceof Node\Identifier) {
+			throw new LogicException();
+		}
+
+		if ($node->name->name === 'yes') {
+			yield new Node\Expr\BooleanNot(new Node\Expr\MethodCall($node->var, 'no'));
+		} else {
+			yield new Node\Expr\BooleanNot(new Node\Expr\MethodCall($node->var, 'yes'));
+		}
+	}
+
+}
diff --git a/tests/Infection/TrinaryLogicMutatorTest.php b/tests/Infection/TrinaryLogicMutatorTest.php
new file mode 100644
index 0000000..8f1e734
--- /dev/null
+++ b/tests/Infection/TrinaryLogicMutatorTest.php
@@ -0,0 +1,74 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Infection;
+
+use Infection\Testing\BaseMutatorTestCase;
+use PHPUnit\Framework\Attributes\CoversClass;
+use PHPUnit\Framework\Attributes\DataProvider;
+
+#[CoversClass(TrinaryLogicMutator::class)]
+final class TrinaryLogicMutatorTest extends BaseMutatorTestCase
+{
+
+	/**
+	 * @param string|string[] $expected
+	 */
+	#[DataProvider('mutationsProvider')]
+	public function testMutator(string $input, $expected = []): void
+	{
+		$this->assertMutatesInput($input, $expected);
+	}
+
+	/**
+	 * @return iterable<string, array{0: string, 1?: string}>
+	 */
+	public static function mutationsProvider(): iterable
+	{
+		yield 'It mutates trinary yes' => [
+			<<<'PHP'
+				<?php
+				$trinary = \PHPStan\TrinaryLogic::createYes();
+				$trinary->yes();
+				PHP
+,
+			<<<'PHP'
+				<?php
+
+				$trinary = \PHPStan\TrinaryLogic::createYes();
+				!$trinary->no();
+				PHP
+,
+		];
+
+		yield 'It mutates trinary no' => [
+			<<<'PHP'
+				<?php
+				$trinary = \PHPStan\TrinaryLogic::createYes();
+				$trinary->no();
+				PHP
+,
+			<<<'PHP'
+				<?php
+
+				$trinary = \PHPStan\TrinaryLogic::createYes();
+				!$trinary->yes();
+				PHP
+,
+		];
+
+		yield 'It skips maybe' => [
+			<<<'PHP'
+				<?php
+				$trinary = \PHPStan\TrinaryLogic::createYes();
+				$trinary->maybe();
+				PHP
+,
+		];
+	}
+
+	protected function getTestedMutatorClassName(): string
+	{
+		return TrinaryLogicMutator::class;
+	}
+
+}
diff --git a/tmp/.gitignore b/tmp/.gitignore
new file mode 100644
index 0000000..37890ca
--- /dev/null
+++ b/tmp/.gitignore
@@ -0,0 +1,3 @@
+*
+!cache
+!.*