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Rust 1.19 regression, treebitmap 0.2.2 #42467

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brson opened this issue Jun 6, 2017 · 3 comments
Closed

Rust 1.19 regression, treebitmap 0.2.2 #42467

brson opened this issue Jun 6, 2017 · 3 comments
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regression-from-stable-to-beta Performance or correctness regression from stable to beta.

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@brson
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brson commented Jun 6, 2017

https://github.com/hroi/treebitmap

commit 67b8a1d591dd13a26b36519a92f5215a53c5c02e
Author: Hroi Sigurdsson <[email protected]>
Date:   Mon Jan 23 16:15:28 2017 +0100

    travis

brian@ip-10-145-43-250:/mnt2/dev⟫ rustc +nightly -Vv
rustc 1.19.0-nightly (0418fa9d3 2017-06-04)
binary: rustc
commit-hash: 0418fa9d382a47d782cc1e195c14573be9c32095
commit-date: 2017-06-04
host: x86_64-unknown-linux-gnu
release: 1.19.0-nightly
LLVM version: 4.0



brian@ip-10-145-43-250:~/dev/slate/treebitmap⟫ cargo +nightly test
   Compiling treebitmap v0.2.2 (file:///mnt2/dev/slate/treebitmap)
error[E0311]: the parameter type `T` may not live long enough
   --> src/tree_bitmap/mod.rs:479:9
    |
479 | impl<T> IntoIterator for TreeBitmap<T> {
    |         ^^^^^^^^^^^^
    |
    = help: consider adding an explicit lifetime bound for `T`
    = note: the parameter type `T` must be valid for the empty lifetime...
note: ...so that the type `T` will meet its required lifetime bounds
   --> src/tree_bitmap/mod.rs:479:9
    |
479 | impl<T> IntoIterator for TreeBitmap<T> {
    |         ^^^^^^^^^^^^

error[E0311]: the parameter type `T` may not live long enough
   --> src/tree_bitmap/mod.rs:479:9
    |
479 | impl<T> IntoIterator for TreeBitmap<T> {
    |         ^^^^^^^^^^^^
    |
    = help: consider adding an explicit lifetime bound for `T`
    = note: the parameter type `T` must be valid for the empty lifetime...
note: ...so that the type `T` will meet its required lifetime bounds
   --> src/tree_bitmap/mod.rs:479:9
    |
479 | impl<T> IntoIterator for TreeBitmap<T> {
    |         ^^^^^^^^^^^^

error[E0311]: the parameter type `T` may not live long enough
   --> src/lib.rs:259:17
    |
259 |         impl<T> IntoIterator for IpLookupTable<$addr_type, T> {
    |                 ^^^^^^^^^^^^
...
273 | impl_ops!(Ipv4Addr);
    | -------------------- in this macro invocation
    |
    = help: consider adding an explicit lifetime bound for `T`
    = note: the parameter type `T` must be valid for the empty lifetime...
note: ...so that the type `T` will meet its required lifetime bounds
   --> src/lib.rs:259:17
    |
259 |         impl<T> IntoIterator for IpLookupTable<$addr_type, T> {
    |                 ^^^^^^^^^^^^
...
273 | impl_ops!(Ipv4Addr);
    | -------------------- in this macro invocation

error[E0311]: the parameter type `T` may not live long enough
   --> src/lib.rs:259:17
    |
259 |         impl<T> IntoIterator for IpLookupTable<$addr_type, T> {
    |                 ^^^^^^^^^^^^
...
273 | impl_ops!(Ipv4Addr);
    | -------------------- in this macro invocation
    |
    = help: consider adding an explicit lifetime bound for `T`
    = note: the parameter type `T` must be valid for the empty lifetime...
note: ...so that the type `T` will meet its required lifetime bounds
   --> src/lib.rs:259:17
    |
259 |         impl<T> IntoIterator for IpLookupTable<$addr_type, T> {
    |                 ^^^^^^^^^^^^
...
273 | impl_ops!(Ipv4Addr);
    | -------------------- in this macro invocation

error[E0311]: the parameter type `T` may not live long enough
   --> src/lib.rs:259:17
    |
259 |         impl<T> IntoIterator for IpLookupTable<$addr_type, T> {
    |                 ^^^^^^^^^^^^
...
274 | impl_ops!(Ipv6Addr);
    | -------------------- in this macro invocation
    |
    = help: consider adding an explicit lifetime bound for `T`
    = note: the parameter type `T` must be valid for the empty lifetime...
note: ...so that the type `T` will meet its required lifetime bounds
   --> src/lib.rs:259:17
    |
259 |         impl<T> IntoIterator for IpLookupTable<$addr_type, T> {
    |                 ^^^^^^^^^^^^
...
274 | impl_ops!(Ipv6Addr);
    | -------------------- in this macro invocation

error[E0311]: the parameter type `T` may not live long enough
   --> src/lib.rs:259:17
    |
259 |         impl<T> IntoIterator for IpLookupTable<$addr_type, T> {
    |                 ^^^^^^^^^^^^
...
274 | impl_ops!(Ipv6Addr);
    | -------------------- in this macro invocation
    |
    = help: consider adding an explicit lifetime bound for `T`
    = note: the parameter type `T` must be valid for the empty lifetime...
note: ...so that the type `T` will meet its required lifetime bounds
   --> src/lib.rs:259:17
    |
259 |         impl<T> IntoIterator for IpLookupTable<$addr_type, T> {
    |                 ^^^^^^^^^^^^
...
274 | impl_ops!(Ipv6Addr);
    | -------------------- in this macro invocation

error: aborting due to previous error(s)

error: Could not compile `treebitmap`.
Build failed, waiting for other jobs to finish...
error[E0311]: the parameter type `T` may not live long enough
   --> src/tree_bitmap/mod.rs:479:9
    |
479 | impl<T> IntoIterator for TreeBitmap<T> {
    |         ^^^^^^^^^^^^
    |
    = help: consider adding an explicit lifetime bound for `T`
    = note: the parameter type `T` must be valid for the empty lifetime...
note: ...so that the type `T` will meet its required lifetime bounds
   --> src/tree_bitmap/mod.rs:479:9
    |
479 | impl<T> IntoIterator for TreeBitmap<T> {
    |         ^^^^^^^^^^^^

error[E0311]: the parameter type `T` may not live long enough
   --> src/tree_bitmap/mod.rs:479:9
    |
479 | impl<T> IntoIterator for TreeBitmap<T> {
    |         ^^^^^^^^^^^^
    |
    = help: consider adding an explicit lifetime bound for `T`
    = note: the parameter type `T` must be valid for the empty lifetime...
note: ...so that the type `T` will meet its required lifetime bounds
   --> src/tree_bitmap/mod.rs:479:9
    |
479 | impl<T> IntoIterator for TreeBitmap<T> {
    |         ^^^^^^^^^^^^

error[E0311]: the parameter type `T` may not live long enough
   --> src/lib.rs:259:17
    |
259 |         impl<T> IntoIterator for IpLookupTable<$addr_type, T> {
    |                 ^^^^^^^^^^^^
...
273 | impl_ops!(Ipv4Addr);
    | -------------------- in this macro invocation
    |
    = help: consider adding an explicit lifetime bound for `T`
    = note: the parameter type `T` must be valid for the empty lifetime...
note: ...so that the type `T` will meet its required lifetime bounds
   --> src/lib.rs:259:17
    |
259 |         impl<T> IntoIterator for IpLookupTable<$addr_type, T> {
    |                 ^^^^^^^^^^^^
...
273 | impl_ops!(Ipv4Addr);
    | -------------------- in this macro invocation

error[E0311]: the parameter type `T` may not live long enough
   --> src/lib.rs:259:17
    |
259 |         impl<T> IntoIterator for IpLookupTable<$addr_type, T> {
    |                 ^^^^^^^^^^^^
...
273 | impl_ops!(Ipv4Addr);
    | -------------------- in this macro invocation
    |
    = help: consider adding an explicit lifetime bound for `T`
    = note: the parameter type `T` must be valid for the empty lifetime...
note: ...so that the type `T` will meet its required lifetime bounds
   --> src/lib.rs:259:17
    |
259 |         impl<T> IntoIterator for IpLookupTable<$addr_type, T> {
    |                 ^^^^^^^^^^^^
...
273 | impl_ops!(Ipv4Addr);
    | -------------------- in this macro invocation

error[E0311]: the parameter type `T` may not live long enough
   --> src/lib.rs:259:17
    |
259 |         impl<T> IntoIterator for IpLookupTable<$addr_type, T> {
    |                 ^^^^^^^^^^^^
...
274 | impl_ops!(Ipv6Addr);
    | -------------------- in this macro invocation
    |
    = help: consider adding an explicit lifetime bound for `T`
    = note: the parameter type `T` must be valid for the empty lifetime...
note: ...so that the type `T` will meet its required lifetime bounds
   --> src/lib.rs:259:17
    |
259 |         impl<T> IntoIterator for IpLookupTable<$addr_type, T> {
    |                 ^^^^^^^^^^^^
...
274 | impl_ops!(Ipv6Addr);
    | -------------------- in this macro invocation

error[E0311]: the parameter type `T` may not live long enough
   --> src/lib.rs:259:17
    |
259 |         impl<T> IntoIterator for IpLookupTable<$addr_type, T> {
    |                 ^^^^^^^^^^^^
...
274 | impl_ops!(Ipv6Addr);
    | -------------------- in this macro invocation
    |
    = help: consider adding an explicit lifetime bound for `T`
    = note: the parameter type `T` must be valid for the empty lifetime...
note: ...so that the type `T` will meet its required lifetime bounds
   --> src/lib.rs:259:17
    |
259 |         impl<T> IntoIterator for IpLookupTable<$addr_type, T> {
    |                 ^^^^^^^^^^^^
...
274 | impl_ops!(Ipv6Addr);
    | -------------------- in this macro invocation

error: aborting due to previous error(s)

error: build failed

cc @hroi
@brson brson added the regression-from-stable-to-nightly Performance or correctness regression from stable to nightly. label Jun 6, 2017
@Mark-Simulacrum
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Bisected to 826d8f3 -- #41914 cc @eddyb

@eddyb
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eddyb commented Jun 6, 2017 •
edited
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Reduces to (note the T: 'a with 'a not used anywhere):

struct Foo<T>(T);

struct IntoIter<T>(T);

impl<'a, T: 'a> Iterator for IntoIter<T> {
    type Item = ();

    fn next(&mut self) -> Option<()> {
        None
    }
}

impl<T> IntoIterator for Foo<T> {
    type Item = ();
    type IntoIter = IntoIter<T>;

    fn into_iter(self) -> IntoIter<T> {
        IntoIter(self.0)
    }
}

fn main() {}

cc @rust-lang/lang I thought we decided that kind of "use" of a parameter is invalid?

EDIT: @nikomatsakis tells me this was allowed for backwards compatibility (and it's harmless).

@eddyb eddyb added regression-from-stable-to-beta Performance or correctness regression from stable to beta. and removed regression-from-stable-to-nightly Performance or correctness regression from stable to nightly. labels Jun 6, 2017
@eddyb eddyb mentioned this issue Jun 6, 2017
Merged
bors added a commit that referenced this issue Jun 7, 2017
@bors
Auto merge of #42482 - eddyb:issue-42467, r=nikomatsakis
37b1f6c 
rustc: T: 'empty always holds for all types.

Fixes #42467 by special-casing `ReEmpty` to always hold, even for parameters.
The reason this is the case is that `ReEmpty` is the result of inferring a region variable with no constraints attached to it, so there is no lifetime a type would contain which would be strictly shorter.

r? @nikomatsakis
@kennytm
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kennytm commented Jun 7, 2017

There should be a lint about the useless lifetime (this line in real code) though.

@hroi hroi mentioned this issue Jun 8, 2017
Closed
@Mark-Simulacrum Mark-Simulacrum mentioned this issue Oct 22, 2017
Closed
nikomatsakis added a commit to nikomatsakis/rust that referenced this issue Feb 6, 2020
@nikomatsakis
add a IsEmpty for use in verified bounds
65fc086 
We currently have a kind of arbitrary check for `Verify` conditions
which says that if the "test region" is `'empty`, then the check
passes. This was added to fix rust-lang#42467 -- it happens to be correct for
the purposes that we use verify bounds for, but it doesn't feel
generally correct. Replace with a more principled test.
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