[Issue 23747] 'auto ref' function return signature does not flag escaping a reference to local variable
https://issues.dlang.org/show_bug.cgi?id=23747
--- Comment #3 from RazvanN ---
(In reply to Mike S from comment #2)
> Ah noted, that is perhaps my mistake then. Looking at the specification
> again with this in mind, I now see how 'auto ref' is deducing the 'refness'
> of a function.
>
> This means 'auto ref' snd 'ref auto' have different meanings then to be
> clear?
>
> - 'auto ref' deducing if it is possible to return by reference, and 'ref
> auto' explicitly indicating return by reference, and deduce the type (e.g.
> auto may be a double if possible return values are 1.0 and 1)
No, `auto ref` or `ref auto` is the same thing. If you want to have a ref
return type that is deduced you can simply omit the return type. The following
example showcases that `auto ref` and `ref auto` are the same thing:
// dmd -c test.d
auto ref fun()
{
int x;
return x;
}
ref auto fun2()
{
int x;
return x;
}
int t;
auto ref fun3()
{
return t;
}
ref auto fun4()
{
return t;
}
ref fun5()
{
return t;
}
ref fun6()
{
int x;
return x; // error
}
pragma(msg, typeof());
pragma(msg, typeof());
pragma(msg, typeof());
pragma(msg, typeof());
pragma(msg, typeof());
--
[Issue 23747] 'auto ref' function return signature does not flag escaping a reference to local variable
https://issues.dlang.org/show_bug.cgi?id=23747 --- Comment #2 from Mike S --- Ah noted, that is perhaps my mistake then. Looking at the specification again with this in mind, I now see how 'auto ref' is deducing the 'refness' of a function. This means 'auto ref' snd 'ref auto' have different meanings then to be clear? - 'auto ref' deducing if it is possible to return by reference, and 'ref auto' explicitly indicating return by reference, and deduce the type (e.g. auto may be a double if possible return values are 1.0 and 1) --
[Issue 23747] 'auto ref' function return signature does not flag escaping a reference to local variable
https://issues.dlang.org/show_bug.cgi?id=23747 RazvanN changed: What|Removed |Added Status|NEW |RESOLVED CC||razvan.nitu1...@gmail.com Resolution|--- |INVALID --- Comment #1 from RazvanN --- This bug report is invalid. All of the `auto ref` functions work as expected. `Auto ref` does not mean "ref + type deduction", but rather "deduce if a function may return by ref + type deduction". In all the situations presented, the compiler sees that it returns a reference to the stack and therefore chooses to drop the ref and return by value. You can add this code and see the types of the functions: pragma(msg, typeof()); -> int function() ref pragma(msg, typeof()); -> int function() pure nothrow @nogc @safe I guess the spec indeed is misleading by stating that "they become ref functions if all return expressions are lvalues". Actually, its more like "they become ref functions, if possible". --
[Issue 23747] 'auto ref' function return signature does not flag escaping a reference to local variable
https://issues.dlang.org/show_bug.cgi?id=23747 Iain Buclaw changed: What|Removed |Added Priority|P1 |P3 --
