Chore

phpstan.neon

@@ -5,4 +5,6 @@ parameters:
         - src
     level: max
     inferPrivatePropertyTypeFromConstructor: true
-    checkUninitializedProperties: true
+    checkUninitializedProperties: true
+    ignoreErrors:
+        - '#Binary operation .* between mixed and mixed results in an error\.#'

src/Evaluator/EvalCallExpression.php

@@ -5,7 +5,6 @@
 namespace Monkey\Evaluator;
 
 use Monkey\Ast\Expressions\CallExpression;
-use Monkey\Ast\Expressions\IdentifierExpression;
 use Monkey\Object\BuiltinFunctionObject;
 use Monkey\Object\ErrorObject;
 use Monkey\Object\FunctionObject;
@@ -57,6 +56,7 @@ public function applyFunction(
         }
 
         if ($monkeyObject instanceof BuiltinFunctionObject) {
+            /** @phpstan-ignore-next-line */
             return call_user_func($monkeyObject->value, ...$args);
         }
 
@@ -70,7 +70,6 @@ public function extendFunctionEnv(FunctionObject $functionObject, array $args):
     {
         $environment = new Environment($functionObject->environment);
 
-        /** @var IdentifierExpression $identifierExpression */
         foreach ($functionObject->parameters as $index => $identifierExpression) {
             $environment->set($identifierExpression->value, $args[$index]);
         }

src/Lexer/Lexer.php

@@ -58,12 +58,21 @@ public function nextToken(): Token
 
             $this->curChar->is('"') => $this->makeTokenAndAdvance(TokenType::STRING, $this->readString()),
 
-            $this->curChar->isLetter() => Token::from(
-                TokenType::fromChar($identifier = $this->readIdentifier()) ?? TokenType::IDENT,
-                $identifier,
-            ),
+            $this->curChar->isLetter() => (function (): Token {
+                $identifier = $this->readIdentifier();
+
+                $type = TokenType::fromChar($identifier) ?? TokenType::IDENT;
+
+                return Token::from($type, $identifier);
+            })(),
+
+            $this->curChar->isDigit() => (function (): Token {
+                $number = $this->readNumber();
+
+                $type = ctype_digit($number) ? TokenType::INT : TokenType::FLOAT;
 
-            $this->curChar->isDigit() => Token::from(ctype_digit($number = $this->readNumber()) ? TokenType::INT : TokenType::FLOAT, $number),
+                return Token::from($type, $number);
+            })(),
 
             $this->curChar->is(self::EOF) => Token::from(TokenType::EOF, self::EOF),
 

src/Object/NullObject.php

@@ -7,13 +7,13 @@
 final readonly class NullObject extends MonkeyObject
 {
     public function __construct(
-        public null $value = null,
+        public null $value,
     ) {
     }
 
     public static function instance(): self
     {
-        return new self();
+        return new self(null);
     }
 
     public function type(): int