synchronized/shared associative array .require error

[cc via Digitalmars-d-learn]

```d
synchronized class SyncTable(KEY, VAL) {
        private VAL[KEY] table;
        auto require(KEY key) {
                return table.require(key);
        }
}
auto table = new shared SyncTable!(string, string);
table.require("abc");
```

Fails to compile:
```
// Error: none of the overloads of template `object.require` are 
callable using argument types `!()(shared(string[string]), 
string)`
```

Tried casting away shared as a workaround but I assume that will 
cause some kind of TLS catastrophe.