Correct implementation for StringType

Author: pepakriz

src/Type/StringType.php

@@ -18,6 +18,16 @@ public function describe(): string
 return 'string';
 }
 
+public function isOffsetAccesible(): TrinaryLogic
+{
+return TrinaryLogic::createYes();
+}
+
+public function getOffsetValueType(): Type
+{
+return new StringType();
+}
+
 public function isCallable(): TrinaryLogic
 {
 return TrinaryLogic::createMaybe();