That doesn't work. It triggers this error:
test2.rs:8:25: 8:30 error: moving out of dereference of immutable & pointer
test2.rs:8 let (ref a, _) = *self;
^~~~~
On Sat, Feb 2, 2013 at 6:21 AM, Niko Matsakis <[email protected]> wrote:
> Interesting! I'm surprised to see that... anyway, try this:
>
> ```
> let (ref a, _) = *self;
> a
> ```
>
> That's how we normally write it. It might workaround the bug (if not, I'd
> like to know!)
>
>
> Niko
>
>
> Alexander Stavonin wrote:
>
> Looks like I'd like to do something extremely difficult %)
>
> 7 impl <T>(T, T): TupleVal<T> {
> 8 fn _1(&self) -> &self/T {
> 9 let &(ref a, _) = self;
> 10 a
> 11 }
>
>
> Assertion failed: (getOperand(0)->getType() ==
> cast<PointerType>(getOperand(1)->getType())->getElementType() && "Ptr must be
> a pointer to Val type!"), function AssertOK, file
> /Volumes/Home/astavonin/Projects/rust/src/llvm/lib/VMCore/Instructions.cpp,
> line 1062.
> zsh: abort rustc test.rs
>
>
> On Feb 2, 2013, at 12:47 PM, Niko Matsakis <[email protected]>
> <[email protected]> wrote:
>
>
> Sorry, I told you wrong. When you write:
>
> let &(a, _) = self;
> &a
>
> You are actually copying the value out of `self` and into the stack variable
> `a`. The error message is telling you that you are returning a pointer into
> your stack frame, which is of course unsafe.
>
> What you actually want is this:
>
> let &(ref a, _) = self;
> a
>
> The `ref` keyword indicates that the `a` variable should be a pointer into
> the value being matched (here, `self`) and not copied out.
>
>
> Niko
>
>
> _______________________________________________
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>
>
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