Re: DIP69 - Implement scope for escape proof references

[Dicebot via Digitalmars-d]

On Monday, 8 December 2014 at 21:12:47 UTC, Walter Bright wrote:
On 12/8/2014 12:54 PM, Dicebot wrote:
struct ByLine
{
    scope string front();
    // ...
}
auto byLine(File file)
{
    return ByLine(file);
}

scope /* ref */ string foo(scope /* ref */ string input)
{
    return input[1..$];
}

void main()
{
    auto r = file.byLine.map!foo;
    string s = r.front; // this should not compile
    string s = r.front.dup; // this should compile

    // how foo signature should look like for this to work?
}

front() should return a 'scope ref string'.

That seems to contradict your other statement:

A 'scope ref' parameter may not be returned as a 'ref' or a 
'scope ref'.

Please check `foo()` once more - it needs to accept scope (ref) 
to be able to accept ByLine.front as an argument. And it also 
needs to pass it down the call chain - but returning `input` by 
reference is illegal according to abovementioned rule.