#69 ensuring that located sources contents can be read

src/SourceLocator/StaticClassMapSourceLocator.php

@@ -49,6 +49,10 @@ protected function createLocatedSource(Identifier $identifier) : ?LocatedSource
             return null;
         }
 
-        return new LocatedSource(file_get_contents($classFile), $classFile);
+        $fileContents = file_get_contents($classFile);
+
+        Assert::that($fileContents)->string();
+
+        return new LocatedSource($fileContents, $classFile);
     }
 }