vrp bug?

[Kagamin via Digitalmars-d-learn]

```
char BitsToChar(in uint bit5)
{
        const uint b=bit5&0x1f;
        return b<10?'0'+b:'a'+(b-10);
}
```
This code can't implicitly convert to char, but a version without 
parentheses `'a'+b-10` can. Is this intended or I miss something?