"Lazy" initialization of structs

[Daniel Tan Fook Hao via Digitalmars-d-learn]

Somehow this code works for me:

```D
auto error (int status, string description){
     struct Error {
         int status;
         string description;
     }
     Error err = {
         status,
         description
     };
     return err.serializeToJson;
}
```

which is supposed to be the same as

```D
struct Error {
     int status;
     string description;
}
auto error (int status, string description){
     Error err = {
         status,
         description
     };
     return err.serializeToJson;
}
```

If I'm reading this right, in the former, the struct is created 
when the function is called in run-time, and the type is then 
inferred after that? I don't really understand the behavior 
behind this.