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 `&[<generic #11>, .. 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
<anon>:5:19: 5:23 error: borrowed value does not live long enough
<anon>:5 let s2 = &[0i];
^~~~
<anon>:2:11: 8:2 note: reference must be valid for the block at
2:10...
<anon>:2 fn main() {
<anon>:3 let s1 = &[0i];
<anon>:4 {
<anon>:5 let s2 = &[0i];
<anon>:6 let s3 = if true { s1 } else { s2 };
<anon>:7 };
...
<anon>:4:5: 7:6 note: ...but borrowed value is only valid for the
block at 4:4
<anon>:4 {
<anon>:5 let s2 = &[0i];
<anon>:6 let s3 = if true { s1 } else { s2 };
<anon>: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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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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