Re: [rust-dev] Bug in lifetime inference?
On Wed, Sep 10, 2014 at 06:26:47PM +0800, Kai Noda wrote:
Hi David,
I stopped worrying about the alleged bug I had reported after I saw
Git HEAD happily compiled it a few days later.
I found your case more interesting because I could compile your code
by changing
assert_eq!(stuff(), &[]);
to
let b = stuff() == &[];
`assert_eq` does the equality check in both directions. It seems
that:
let b = &[] == stuff();
still fails to compile:
test.rs:6:20: 6:27 error: mismatched types: expected `&[, .. 0]`,
found `&'static [uint]` (expected vector, found vector)
test.rs:6 let b = &[] == stuff();
^~~
test.rs:6:13: 6:27 error: cannot determine a type for this bounded type
parameter: unconstrained type
test.rs:6 let b = &[] == stuff();
which is basically the same error seen in the expansion of the
`assert_eq`.
It seems that the array literal cannot be used on the left side of a
comparison.
If anything, the "expected vector, found vector" isn't particularly
helpful.
David
Regards,
Kai
2014-09-10 8:22 GMT+08:00 David Brown <[1]dav...@davidb.org>:
I've seen something similar recently, with this code:
--
fn main() {
// Fails.
assert_eq!(stuff(), &[]);
// Works
let tmp: &'static [uint] = &[];
assert_eq!(stuff(), tmp);
}
static simple: &'static [uint] = &[1, 2];
fn stuff() -> &'static [uint] {
simple
}
--
The failing code worked a week or so ago. Similar issue in that I
can
make it work by giving an explicit type for the literal array.
David
On Sat, Aug 30, 2014 at 04:52:00PM +0800, Kai Noda wrote:
Hi Rusters,
I'm very new to Rust, so I'd like you to check if this is really a
compiler bug or not.
fn main() {
let s1 = &[0i];
{
let s2 = &[0i];
let s3 = if true { s1 } else { s2 };
};
}
[1][2]http://is.gd/NCeGpl
:5:19: 5:23 error: borrowed value does not live long enough
:5 let s2 = &[0i];
^~~~
:2:11: 8:2 note: reference must be valid for the block at
2:10...
:2 fn main() {
:3 let s1 = &[0i];
:4 {
:5 let s2 = &[0i];
:6 let s3 = if true { s1 } else { s2 };
:7 };
...
:4:5: 7:6 note: ...but borrowed value is only valid for the
block at 4:4
:4 {
:5 let s2 = &[0i];
:6 let s3 = if true { s1 } else { s2 };
:7 };
error: aborting due to previous error
Seems like s1 and s2 are inferred as &[int, ..1] and when I
manually
type them as &[int], it successfully compiles.
fn main() {
let s1: &[int] = &[0i];
{
let s2: &[int] = &[0i];
let s3 = if true { s1 } else { s2 };
};
}
Putting s1 and s2 into a single block also satisfies the compiler.
fn main() {
let s1 = &[0i];
let s2 = &[0i];
let s3 = if true { s1 } else { s2 };
}
I came from C++ and I think the way I take reference of a fixed
vector
literal is correct.
[2][3]http://doc.rust-lang.org/rust.html#pointer-types
I was originally trying to fix this line which doesn't compile
with
the nightly build of Rust:
[3][4]https://github.com/servo/rust-url/blob/master/src/form_urlencoded.rs#L55
No similar issue is filed here:
[4][5]https://github.com/rust-lang/rust/labels/A-lifetimes
Best regards,
Kai
野田 開 <[5][6]noda...@gmail.com>
References
Visible links
1. [7]http://is.gd/NCeGpl
2. [8]http://doc.rust-lang.org/rust.html#pointer-types
3.
[9]https://github.com/servo/rust-url/blob/master/src/form_urlencoded.rs#L55
4. [10]https://github.com/rust-lang/rust/labels/A-lifetimes
5. mailto:[11]noda...@gmail.com
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[13]https://mail.mozilla.org/listinfo/rust-dev
References
Visible links
1. mailto:dav...@davidb.org
2. http://is.gd/NCeGpl
3. http://doc.rust-lang.org/rust.html#pointer-types
4. https://github.com/servo/rust-url/blob/master/src/form_urlencoded.rs#L55
5. https://github.com/rust-lang/rust/labels/A-lifetimes
6. mailto:noda...@gmail.com
7. http://is.gd/NCeGpl
8. http://doc.rust-lang.org/rust.html#pointer-types
9. https://github.com/servo/rust-url/blob/master/src/form_urlencoded.rs#L55
10. https://github.com/rust-lang/rust/labels/A-lifetimes
11. mailto:noda...@gmail.com
12. mailto:Rust-dev@mozilla.org
13. https://mail.mozilla.org/listinfo/rust-dev
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Re: [rust-dev] Bug in lifetime inference?
Hi David,
I stopped worrying about the alleged bug I had reported after I saw Git
HEAD happily compiled it a few days later.
I found your case more interesting because I could compile your code by
changing
assert_eq!(stuff(), &[]);
to
let b = stuff() == &[];
Regards,
Kai
2014-09-10 8:22 GMT+08:00 David Brown :
> I've seen something similar recently, with this code:
>
> --
> fn main() {
>// Fails.
>assert_eq!(stuff(), &[]);
>
>// Works
>let tmp: &'static [uint] = &[];
>assert_eq!(stuff(), tmp);
> }
>
> static simple: &'static [uint] = &[1, 2];
>
> fn stuff() -> &'static [uint] {
>simple
> }
> --
>
> The failing code worked a week or so ago. Similar issue in that I can
> make it work by giving an explicit type for the literal array.
>
> David
>
> On Sat, Aug 30, 2014 at 04:52:00PM +0800, Kai Noda wrote:
>
>> Hi Rusters,
>> I'm very new to Rust, so I'd like you to check if this is really a
>> compiler bug or not.
>> fn main() {
>> let s1 = &[0i];
>> {
>> let s2 = &[0i];
>> let s3 = if true { s1 } else { s2 };
>> };
>> }
>> [1]http://is.gd/NCeGpl
>>
>>
>> :5:19: 5:23 error: borrowed value does not live long enough
>> :5 let s2 = &[0i];
>> ^~~~
>> :2:11: 8:2 note: reference must be valid for the block at 2:10...
>> :2 fn main() {
>> :3 let s1 = &[0i];
>> :4 {
>> :5 let s2 = &[0i];
>> :6 let s3 = if true { s1 } else { s2 };
>> :7 };
>> ...
>> :4:5: 7:6 note: ...but borrowed value is only valid for the block
>> at 4:4
>> :4 {
>> :5 let s2 = &[0i];
>> :6 let s3 = if true { s1 } else { s2 };
>> :7 };
>> error: aborting due to previous error
>>
>> Seems like s1 and s2 are inferred as &[int, ..1] and when I manually
>> type them as &[int], it successfully compiles.
>> fn main() {
>> let s1: &[int] = &[0i];
>> {
>> let s2: &[int] = &[0i];
>> let s3 = if true { s1 } else { s2 };
>> };
>> }
>> Putting s1 and s2 into a single block also satisfies the compiler.
>> fn main() {
>> let s1 = &[0i];
>> let s2 = &[0i];
>> let s3 = if true { s1 } else { s2 };
>> }
>> I came from C++ and I think the way I take reference of a fixed vector
>> literal is correct.
>> [2]http://doc.rust-lang.org/rust.html#pointer-types
>> I was originally trying to fix this line which doesn't compile with
>> the nightly build of Rust:
>> [3]https://github.com/servo/rust-url/blob/master/src/form_
>> urlencoded.rs#L55
>> No similar issue is filed here:
>> [4]https://github.com/rust-lang/rust/labels/A-lifetimes
>> Best regards,
>> Kai
>> 野田 開 <[5]noda...@gmail.com>
>>
>> References
>>
>> Visible links
>> 1. http://is.gd/NCeGpl
>> 2. http://doc.rust-lang.org/rust.html#pointer-types
>> 3. https://github.com/servo/rust-url/blob/master/src/form_
>> urlencoded.rs#L55
>> 4. https://github.com/rust-lang/rust/labels/A-lifetimes
>> 5. mailto:noda...@gmail.com
>>
>
> ___
>> Rust-dev mailing list
>> Rust-dev@mozilla.org
>> https://mail.mozilla.org/listinfo/rust-dev
>>
>
>
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Rust-dev@mozilla.org
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Re: [rust-dev] Bug in lifetime inference?
I've seen something similar recently, with this code:
--
fn main() {
// Fails.
assert_eq!(stuff(), &[]);
// Works
let tmp: &'static [uint] = &[];
assert_eq!(stuff(), tmp);
}
static simple: &'static [uint] = &[1, 2];
fn stuff() -> &'static [uint] {
simple
}
--
The failing code worked a week or so ago. Similar issue in that I can
make it work by giving an explicit type for the literal array.
David
On Sat, Aug 30, 2014 at 04:52:00PM +0800, Kai Noda wrote:
Hi Rusters,
I'm very new to Rust, so I'd like you to check if this is really a
compiler bug or not.
fn main() {
let s1 = &[0i];
{
let s2 = &[0i];
let s3 = if true { s1 } else { s2 };
};
}
[1]http://is.gd/NCeGpl
:5:19: 5:23 error: borrowed value does not live long enough
:5 let s2 = &[0i];
^~~~
:2:11: 8:2 note: reference must be valid for the block at 2:10...
:2 fn main() {
:3 let s1 = &[0i];
:4 {
:5 let s2 = &[0i];
:6 let s3 = if true { s1 } else { s2 };
:7 };
...
:4:5: 7:6 note: ...but borrowed value is only valid for the block at 4:4
:4 {
:5 let s2 = &[0i];
:6 let s3 = if true { s1 } else { s2 };
:7 };
error: aborting due to previous error
Seems like s1 and s2 are inferred as &[int, ..1] and when I manually
type them as &[int], it successfully compiles.
fn main() {
let s1: &[int] = &[0i];
{
let s2: &[int] = &[0i];
let s3 = if true { s1 } else { s2 };
};
}
Putting s1 and s2 into a single block also satisfies the compiler.
fn main() {
let s1 = &[0i];
let s2 = &[0i];
let s3 = if true { s1 } else { s2 };
}
I came from C++ and I think the way I take reference of a fixed vector
literal is correct.
[2]http://doc.rust-lang.org/rust.html#pointer-types
I was originally trying to fix this line which doesn't compile with
the nightly build of Rust:
[3]https://github.com/servo/rust-url/blob/master/src/form_urlencoded.rs#L55
No similar issue is filed here:
[4]https://github.com/rust-lang/rust/labels/A-lifetimes
Best regards,
Kai
野田 開 <[5]noda...@gmail.com>
References
Visible links
1. http://is.gd/NCeGpl
2. http://doc.rust-lang.org/rust.html#pointer-types
3. https://github.com/servo/rust-url/blob/master/src/form_urlencoded.rs#L55
4. https://github.com/rust-lang/rust/labels/A-lifetimes
5. mailto:noda...@gmail.com
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