[Issue 15413] New: Foreach over range with @disable this doesn't work

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=15413

          Issue ID: 15413
           Summary: Foreach over range with @disable this doesn't work
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P1
         Component: dmd
          Assignee: nobody at puremagic.com
          Reporter: pro.mathias.lang at gmail.com

```
public struct IRange
{
    int[] data;

    public this(int[] d) { this.data = d; }
    @disable this(this);
    public int front () @property { return data[0]; }
    public bool empty () @property { return !!data.length; }
    public void popFront () { data = data[1..$]; }
}

void main ()
{
    auto ir = IRange([1,2,3,4]);
    foreach (v; ir)
    {
    }
}
```

Obviously it happens because it lowers to:
```
for (auto __r = ir; !__r.empty; __r.popFront()) {
        auto v = __r.front;
    }
```


Which means that input ranges which behaves as forward ranges when copied will
have an implicit `.save` here. So fixing this bug could potentially affect a
lot of code.

Related: https://issues.dlang.org/show_bug.cgi?id=4347 (note: I didn't use that
issue because I don't propose we do an implicit `.save`, but rather we get rid
of it in all circumstances).

--