`#pragma once` no working inside `import * from as`

#### a.hexpat
```
#pragma once 

import std.io;
std::print("{}", "Import a");
```

#### b.hexpat
```
#pragma once

import a;
```


The following code will output `Import a` twice. I am expecting that module `a` should be executed only once as it is guarded with `pragma once`.
```
import a;
import * from b as B;

B b @ 0;
```