diff --git a/.github/workflows/checks.yml b/.github/workflows/checks.yml
index 6202f32..575b25e 100644
--- a/.github/workflows/checks.yml
+++ b/.github/workflows/checks.yml
@@ -10,7 +10,6 @@ jobs:
       fail-fast: false
       matrix:
         php:
-          - "8.1"
           - "8.2"
           - "8.3"
         dependencies:
@@ -43,8 +42,8 @@ jobs:
       fail-fast: false
       matrix:
         php:
-          - "8.1"
           - "8.2"
+          - "8.3"
         dependencies:
           - ""
           - "--prefer-lowest"
@@ -74,7 +73,6 @@ jobs:
       fail-fast: false
       matrix:
         php:
-          - "8.1"
           - "8.2"
           - "8.3"
         dependencies:
@@ -106,7 +104,6 @@ jobs:
       fail-fast: false
       matrix:
         php:
-          - "8.1"
           - "8.2"
           - "8.3"
         dependencies:
@@ -140,7 +137,6 @@ jobs:
       fail-fast: false
       matrix:
         php:
-          - "8.1"
           - "8.2"
           - "8.3"
         dependencies:
@@ -171,9 +167,9 @@ jobs:
             --coverage-clover=build/coverage/clover.xml
 
       - name: Upload coverage
-        uses: actions/upload-artifact@v3
+        uses: actions/upload-artifact@v4
         with:
-          name: coverage-${{ matrix.php }}
+          name: coverage-${{ matrix.php }}-${{ matrix.dependencies }}
           path: build/coverage/
 
   infection:
@@ -185,7 +181,6 @@ jobs:
       fail-fast: false
       matrix:
         php:
-          - "8.1"
           - "8.2"
           - "8.3"
         dependencies:
@@ -211,9 +206,9 @@ jobs:
         run: composer update --no-progress --no-interaction ${{ matrix.dependencies }}
 
       - name: Download coverage
-        uses: actions/download-artifact@v3
+        uses: actions/download-artifact@v4
         with:
-          name: coverage-${{ matrix.php }}
+          name: coverage-${{ matrix.php }}-${{ matrix.dependencies }}
           path: build/coverage/
 
       - name: Infection coverage of changed lines
@@ -231,10 +226,10 @@ jobs:
             -jmax
 
       - name: Save Infection result
-        uses: actions/upload-artifact@v3
+        uses: actions/upload-artifact@v4
         if: always()
         with:
-          name: infection-log-${{ matrix.php }}.txt
+          name: infection-log-${{ matrix.php }}-${{ matrix.dependencies }}.txt
           path: infection-log.txt
 
   bc-breaks:
diff --git a/composer.json b/composer.json
index a1260fa..3c94de1 100644
--- a/composer.json
+++ b/composer.json
@@ -4,21 +4,22 @@
     "license": "MIT",
     "type": "library",
     "require": {
-        "php": ">=8.1",
+        "php": ">=8.2",
         "ext-ctype": "*"
     },
     "require-dev": {
-        "eventjet/coding-standard": "^3.12",
+        "eventjet/coding-standard": "^3.18",
+        "friendsofphp/php-cs-fixer": "^3.75",
         "infection/infection": "^0.27.0",
         "maglnet/composer-require-checker": "^4.6",
         "phpstan/extension-installer": "^1.3",
-        "phpstan/phpstan": "^1.10.34",
-        "phpstan/phpstan-phpunit": "^1.3",
-        "phpstan/phpstan-strict-rules": "^1.5",
+        "phpstan/phpstan": "^1.12.25",
+        "phpstan/phpstan-phpunit": "^1.4.2",
+        "phpstan/phpstan-strict-rules": "^1.6.2",
         "phpunit/phpunit": "^10.2",
         "psalm/plugin-phpunit": "^0.18.4",
         "roave/backward-compatibility-check": "^8.3",
-        "vimeo/psalm": "^5.16"
+        "vimeo/psalm": "^5.26.1"
     },
     "minimum-stability": "stable",
     "autoload": {
diff --git a/src/And_.php b/src/And_.php
index 4a2c65e..df031c7 100644
--- a/src/And_.php
+++ b/src/And_.php
@@ -5,6 +5,7 @@
 namespace Eventjet\Ausdruck;
 
 use Eventjet\Ausdruck\Parser\Span;
+use Override;
 
 use function get_debug_type;
 use function is_bool;
@@ -25,6 +26,7 @@ public function __toString(): string
         return sprintf('%s && %s', $this->left, $this->right);
     }
 
+    #[Override]
     public function evaluate(Scope $scope): bool
     {
         $left = $this->left->evaluate($scope);
@@ -37,6 +39,7 @@ public function evaluate(Scope $scope): bool
         return $left && $right;
     }
 
+    #[Override]
     public function equals(Expression $other): bool
     {
         return $other instanceof self
@@ -44,11 +47,13 @@ public function equals(Expression $other): bool
             && $this->right->equals($other->right);
     }
 
+    #[Override]
     public function getType(): Type
     {
         return Type::bool();
     }
 
+    #[Override]
     public function location(): Span
     {
         return $this->left->location()->to($this->right->location());
diff --git a/src/Call.php b/src/Call.php
index 83fcbbf..3b3777e 100644
--- a/src/Call.php
+++ b/src/Call.php
@@ -5,6 +5,7 @@
 namespace Eventjet\Ausdruck;
 
 use Eventjet\Ausdruck\Parser\Span;
+use Override;
 use Throwable;
 
 use function array_map;
@@ -57,6 +58,7 @@ public function __toString(): string
         return sprintf('%s.%s:%s(%s)', $this->target, $this->name, $this->type, implode(', ', $this->arguments));
     }
 
+    #[Override]
     public function evaluate(Scope $scope): mixed
     {
         $func = $scope->func($this->name);
@@ -72,6 +74,7 @@ public function evaluate(Scope $scope): mixed
         }
     }
 
+    #[Override]
     public function equals(Expression $other): bool
     {
         return $other instanceof self
@@ -81,6 +84,7 @@ public function equals(Expression $other): bool
             && self::compareArguments($this->arguments, $other->arguments);
     }
 
+    #[Override]
     public function getType(): Type
     {
         return $this->type;
diff --git a/src/Eq.php b/src/Eq.php
index 2d1eaed..dacd584 100644
--- a/src/Eq.php
+++ b/src/Eq.php
@@ -5,6 +5,7 @@
 namespace Eventjet\Ausdruck;
 
 use Eventjet\Ausdruck\Parser\Span;
+use Override;
 
 use function sprintf;
 
@@ -23,11 +24,13 @@ public function __toString(): string
         return sprintf('%s === %s', $this->left, $this->right);
     }
 
+    #[Override]
     public function evaluate(Scope $scope): bool
     {
         return $this->left->evaluate($scope) === $this->right->evaluate($scope);
     }
 
+    #[Override]
     public function equals(Expression $other): bool
     {
         return $other instanceof self
@@ -35,11 +38,13 @@ public function equals(Expression $other): bool
             && $this->right->equals($other->right);
     }
 
+    #[Override]
     public function getType(): Type
     {
         return Type::bool();
     }
 
+    #[Override]
     public function location(): Span
     {
         return $this->left->location()->to($this->right->location());
diff --git a/src/Expression.php b/src/Expression.php
index 735c3a8..d15cb3f 100644
--- a/src/Expression.php
+++ b/src/Expression.php
@@ -19,30 +19,22 @@ public function eq(self $other): Eq
 
     public function subtract(self $subtrahend): Subtract
     {
-        /** @var self $self */
-        $self = $this;
-        return Expr::subtract($self, $subtrahend);
+        return Expr::subtract($this, $subtrahend);
     }
 
     public function gt(self $right): Gt
     {
-        /** @var self $self */
-        $self = $this;
-        return Expr::gt($self, $right);
+        return Expr::gt($this, $right);
     }
 
     public function or_(self $other): Or_
     {
-        /** @var self $self */
-        $self = $this;
-        return Expr::or_($self, $other);
+        return Expr::or_($this, $other);
     }
 
     public function and_(self $other): self
     {
-        /** @var self $self */
-        $self = $this;
-        return Expr::and_($self, $other);
+        return Expr::and_($this, $other);
     }
 
     /**
diff --git a/src/Get.php b/src/Get.php
index 72d2b16..a6e882e 100644
--- a/src/Get.php
+++ b/src/Get.php
@@ -6,6 +6,7 @@
 
 use Eventjet\Ausdruck\Parser\Span;
 use Eventjet\Ausdruck\Parser\TypeHint;
+use Override;
 
 use function get_debug_type;
 use function sprintf;
@@ -34,6 +35,7 @@ public function __toString(): string
         return sprintf('%s%s', $this->name, $this->typeHint);
     }
 
+    #[Override]
     public function evaluate(Scope $scope): mixed
     {
         /** @psalm-suppress MixedAssignment */
@@ -57,6 +59,7 @@ public function evaluate(Scope $scope): mixed
         }
     }
 
+    #[Override]
     public function equals(Expression $other): bool
     {
         return $other instanceof self
@@ -64,6 +67,7 @@ public function equals(Expression $other): bool
             && $this->typeHint->type->equals($other->typeHint->type);
     }
 
+    #[Override]
     public function getType(): Type
     {
         return $this->typeHint->type;
diff --git a/src/Gt.php b/src/Gt.php
index 93c1f52..f38de1a 100644
--- a/src/Gt.php
+++ b/src/Gt.php
@@ -5,6 +5,7 @@
 namespace Eventjet\Ausdruck;
 
 use Eventjet\Ausdruck\Parser\Span;
+use Override;
 
 use function sprintf;
 
@@ -23,11 +24,13 @@ public function __toString(): string
         return sprintf('%s > %s', $this->left, $this->right);
     }
 
+    #[Override]
     public function evaluate(Scope $scope): bool
     {
         return $this->left->evaluate($scope) > $this->right->evaluate($scope);
     }
 
+    #[Override]
     public function equals(Expression $other): bool
     {
         return $other instanceof self
@@ -35,11 +38,13 @@ public function equals(Expression $other): bool
             && $this->right->equals($other->right);
     }
 
+    #[Override]
     public function getType(): Type
     {
         return Type::bool();
     }
 
+    #[Override]
     public function location(): Span
     {
         return $this->left->location()->to($this->right->location());
diff --git a/src/Lambda.php b/src/Lambda.php
index dfd1b1a..5eb41a5 100644
--- a/src/Lambda.php
+++ b/src/Lambda.php
@@ -5,6 +5,7 @@
 namespace Eventjet\Ausdruck;
 
 use Eventjet\Ausdruck\Parser\Span;
+use Override;
 
 use function array_map;
 use function implode;
@@ -34,6 +35,7 @@ public function __toString(): string
     /**
      * @return callable(Scope): mixed
      */
+    #[Override]
     public function evaluate(Scope $scope): callable
     {
         return function (mixed ...$params) use ($scope): mixed {
@@ -45,6 +47,7 @@ public function evaluate(Scope $scope): callable
         };
     }
 
+    #[Override]
     public function equals(Expression $other): bool
     {
         return $other instanceof self
@@ -52,6 +55,7 @@ public function equals(Expression $other): bool
             && $this->body->equals($other->body);
     }
 
+    #[Override]
     public function getType(): Type
     {
         return Type::func($this->body->getType(), array_map(static fn(string $_name) => Type::any(), $this->parameters));
diff --git a/src/ListLiteral.php b/src/ListLiteral.php
index 5c434c9..634d962 100644
--- a/src/ListLiteral.php
+++ b/src/ListLiteral.php
@@ -5,6 +5,7 @@
 namespace Eventjet\Ausdruck;
 
 use Eventjet\Ausdruck\Parser\Span;
+use Override;
 
 use function array_map;
 use function implode;
@@ -23,6 +24,7 @@ public function __toString()
         return '[' . implode(', ', $this->elements) . ']';
     }
 
+    #[Override]
     public function location(): Span
     {
         return $this->location;
@@ -31,6 +33,7 @@ public function location(): Span
     /**
      * @return list<mixed>
      */
+    #[Override]
     public function evaluate(Scope $scope): array
     {
         return array_map(
@@ -39,6 +42,7 @@ public function evaluate(Scope $scope): array
         );
     }
 
+    #[Override]
     public function equals(Expression $other): bool
     {
         if (!$other instanceof self) {
@@ -53,6 +57,7 @@ public function equals(Expression $other): bool
         return true;
     }
 
+    #[Override]
     public function getType(): Type
     {
         $elementType = null;
diff --git a/src/Literal.php b/src/Literal.php
index b0cde23..ae3de93 100644
--- a/src/Literal.php
+++ b/src/Literal.php
@@ -5,6 +5,7 @@
 namespace Eventjet\Ausdruck;
 
 use Eventjet\Ausdruck\Parser\Span;
+use Override;
 
 use function array_is_list;
 use function array_map;
@@ -65,17 +66,20 @@ public function __toString(): string
         return self::dumpValue($this->value);
     }
 
+    #[Override]
     public function evaluate(Scope $scope): mixed
     {
         return $this->value;
     }
 
+    #[Override]
     public function equals(Expression $other): bool
     {
         return $other instanceof self
             && $this->value === $other->value;
     }
 
+    #[Override]
     public function getType(): Type
     {
         return Type::fromValue($this->value);
diff --git a/src/Negative.php b/src/Negative.php
index 7e944d3..70f51d7 100644
--- a/src/Negative.php
+++ b/src/Negative.php
@@ -5,6 +5,7 @@
 namespace Eventjet\Ausdruck;
 
 use Eventjet\Ausdruck\Parser\Span;
+use Override;
 
 use function is_float;
 use function is_int;
@@ -24,6 +25,7 @@ public function __toString(): string
         return sprintf('-%s', $this->expression);
     }
 
+    #[Override]
     public function evaluate(Scope $scope): float|int
     {
         $value = $this->expression->evaluate($scope);
@@ -33,12 +35,14 @@ public function evaluate(Scope $scope): float|int
         return -$value;
     }
 
+    #[Override]
     public function equals(Expression $other): bool
     {
         return $other instanceof self
             && $this->expression->equals($other->expression);
     }
 
+    #[Override]
     public function getType(): Type
     {
         return $this->expression->getType();
diff --git a/src/Or_.php b/src/Or_.php
index edfa87e..205c378 100644
--- a/src/Or_.php
+++ b/src/Or_.php
@@ -5,6 +5,7 @@
 namespace Eventjet\Ausdruck;
 
 use Eventjet\Ausdruck\Parser\Span;
+use Override;
 
 use function get_debug_type;
 use function is_bool;
@@ -25,6 +26,7 @@ public function __toString(): string
         return sprintf('%s || %s', $this->left, $this->right);
     }
 
+    #[Override]
     public function evaluate(Scope $scope): bool
     {
         $left = $this->left->evaluate($scope);
@@ -37,6 +39,7 @@ public function evaluate(Scope $scope): bool
         return $left || $right;
     }
 
+    #[Override]
     public function equals(Expression $other): bool
     {
         return $other instanceof self
@@ -44,11 +47,13 @@ public function equals(Expression $other): bool
             && $this->right->equals($other->right);
     }
 
+    #[Override]
     public function getType(): Type
     {
         return Type::bool();
     }
 
+    #[Override]
     public function location(): Span
     {
         return $this->left->location()->to($this->right->location());
diff --git a/src/Parser/Literal.php b/src/Parser/Literal.php
index a99e520..58b8c31 100644
--- a/src/Parser/Literal.php
+++ b/src/Parser/Literal.php
@@ -4,6 +4,7 @@
 
 namespace Eventjet\Ausdruck\Parser;
 
+use Override;
 use Stringable;
 
 use function is_string;
@@ -23,6 +24,7 @@ public function __construct(public readonly string|int|float $value)
     {
     }
 
+    #[Override]
     public function __toString(): string
     {
         if (is_string($this->value)) {
diff --git a/src/Parser/Span.php b/src/Parser/Span.php
index d2d3219..4596cf2 100644
--- a/src/Parser/Span.php
+++ b/src/Parser/Span.php
@@ -4,6 +4,7 @@
 
 namespace Eventjet\Ausdruck\Parser;
 
+use Override;
 use Stringable;
 
 use function sprintf;
@@ -33,6 +34,7 @@ public static function char(int $line, int $column): self
         return new self($line, $column, $line, $column);
     }
 
+    #[Override]
     public function __toString(): string
     {
         return sprintf(
diff --git a/src/Parser/TypeHint.php b/src/Parser/TypeHint.php
index 4c825a7..84cea9b 100644
--- a/src/Parser/TypeHint.php
+++ b/src/Parser/TypeHint.php
@@ -5,6 +5,7 @@
 namespace Eventjet\Ausdruck\Parser;
 
 use Eventjet\Ausdruck\Type;
+use Override;
 use Stringable;
 
 use function sprintf;
@@ -15,6 +16,7 @@ public function __construct(public readonly Type $type, public readonly bool $ex
     {
     }
 
+    #[Override]
     public function __toString(): string
     {
         if (!$this->explicit) {
diff --git a/src/Parser/TypeNode.php b/src/Parser/TypeNode.php
index c9008de..42d5f4d 100644
--- a/src/Parser/TypeNode.php
+++ b/src/Parser/TypeNode.php
@@ -4,6 +4,7 @@
 
 namespace Eventjet\Ausdruck\Parser;
 
+use Override;
 use Stringable;
 
 use function implode;
@@ -25,6 +26,7 @@ public function __construct(
     ) {
     }
 
+    #[Override]
     public function __toString(): string
     {
         return $this->args === []
diff --git a/src/Subtract.php b/src/Subtract.php
index 46e82f0..aed892a 100644
--- a/src/Subtract.php
+++ b/src/Subtract.php
@@ -5,6 +5,7 @@
 namespace Eventjet\Ausdruck;
 
 use Eventjet\Ausdruck\Parser\Span;
+use Override;
 
 use function get_debug_type;
 use function gettype;
@@ -27,6 +28,7 @@ public function __toString(): string
         return sprintf('%s - %s', $this->minuend, $this->subtrahend);
     }
 
+    #[Override]
     public function evaluate(Scope $scope): int|float
     {
         /** @var mixed $minuend */
@@ -57,6 +59,7 @@ public function evaluate(Scope $scope): int|float
         );
     }
 
+    #[Override]
     public function equals(Expression $other): bool
     {
         return $other instanceof self
@@ -64,11 +67,13 @@ public function equals(Expression $other): bool
             && $this->subtrahend->equals($other->subtrahend);
     }
 
+    #[Override]
     public function getType(): Type
     {
         return $this->minuend->getType();
     }
 
+    #[Override]
     public function location(): Span
     {
         return $this->minuend->location()->to($this->subtrahend->location());
diff --git a/src/Type.php b/src/Type.php
index 28909e4..bd36369 100644
--- a/src/Type.php
+++ b/src/Type.php
@@ -5,12 +5,14 @@
 namespace Eventjet\Ausdruck;
 
 use InvalidArgumentException;
+use Override;
 use Stringable;
 
 use function array_is_list;
 use function array_key_first;
 use function array_shift;
 use function array_slice;
+use function assert;
 use function gettype;
 use function implode;
 use function in_array;
@@ -140,9 +142,11 @@ private static function keyAndValueTypeFromArray(array $value): array
         return [self::fromValue($firstKey), self::fromValue($value[$firstKey])];
     }
 
+    #[Override]
     public function __toString(): string
     {
         if ($this->name === 'Func') {
+            assert($this->args !== []);
             $args = $this->args;
             $returnType = array_shift($args);
             return sprintf('func(%s): %s', implode(', ', $args), $returnType);
diff --git a/tests/unit/Parser/ExpressionParserTest.php b/tests/unit/Parser/ExpressionParserTest.php
index 732ecfc..bb2c22e 100644
--- a/tests/unit/Parser/ExpressionParserTest.php
+++ b/tests/unit/Parser/ExpressionParserTest.php
@@ -334,15 +334,15 @@ public static function syntaxErrorLocationCases(): iterable
         yield [
             <<<'EXPR'
 
-              :list<int>
-            EXPR,
+                  :list<int>
+                EXPR,
             Span::char(2, 3),
         ];
         yield [
             <<<'EXPR'
-              foo:string
-                === :string
-            EXPR,
+                  foo:string
+                    === :string
+                EXPR,
             Span::char(2, 9),
         ];
     }
diff --git a/tests/unit/Parser/TypeParserTest.php b/tests/unit/Parser/TypeParserTest.php
index b29b5bb..a52588b 100644
--- a/tests/unit/Parser/TypeParserTest.php
+++ b/tests/unit/Parser/TypeParserTest.php
@@ -10,7 +10,6 @@
 use LogicException;
 use PHPUnit\Framework\TestCase;
 
-use function assert;
 use function explode;
 use function implode;
 use function preg_match;
@@ -37,9 +36,9 @@ public static function syntaxErrorCases(): iterable
         ];
         yield 'Empty string' => [
             <<<'AUSDRUCK'
-            
-            =
-            AUSDRUCK,
+                
+                =
+                AUSDRUCK,
             'Invalid type ""',
         ];
         yield 'Whitespace-only string' => [
@@ -48,9 +47,9 @@ public static function syntaxErrorCases(): iterable
         ];
         yield 'Arrow' => [
             <<<'AUSDRUCK'
-            ->
-            ==
-            AUSDRUCK,
+                ->
+                ==
+                AUSDRUCK,
             'Expected type, got ->',
         ];
     }
@@ -76,7 +75,7 @@ public function testSyntaxErrors(string $type, string $expectedMessage): void
             }
             $startCol = strlen($matches['indent']) + 1;
             $endCol = strlen($matches['indent']) + strlen($matches['marker']);
-            assert($endCol > 0, 'End column can\'t be lower than 1 because the marker is at least one character long');
+            /** @psalm-suppress InvalidArgument Psalm doesn't analyze regular expressions */
             $expectedSpan = new Span($lineNumber, $startCol, $lineNumber, $endCol);
             unset($lines[$lineIndex]);
         }