Fix parser psalm errors

Author: Kirill Nesmeyanov

src/Exception/FeatureNotAllowedException.php

@@ -6,6 +6,10 @@
 
 final class FeatureNotAllowedException extends SemanticException
 {
+    /**
+     * @param non-empty-string $name
+     * @param int<0, max> $offset
+     */
     public static function fromFeature(string $name, int $offset = 0): self
     {
         $message = \sprintf('%s not allowed by parser configuration', $name);

src/Parser.php

@@ -120,6 +120,8 @@ private function createLexer(array $grammar): Lexer
      */
     public function parse(#[Language('PHP')] mixed $source): ?TypeStatement
     {
+        $this->lastProcessedTokenOffset = 0;
+
         /** @psalm-suppress PossiblyInvalidArgument */
         $source = File::new($source);
 
@@ -132,9 +134,12 @@ public function parse(#[Language('PHP')] mixed $source): ?TypeStatement
                 foreach ($this->parser->parse($source) as $stmt) {
                     if ($stmt instanceof TypeStatement) {
                         $context = $this->parser->getLastExecutionContext();
-                        $token = $context->buffer->current();
 
-                        $this->lastProcessedTokenOffset = $token->getOffset();
+                        if ($context !== null) {
+                            $token = $context->buffer->current();
+
+                            $this->lastProcessedTokenOffset = $token->getOffset();
+                        }
 
                         return $stmt;
                     }