ICEs and transmutes in safe Rust with associated_type_defaults and generic_associated_types #74816
Labels
A-associated-items
Area: Associated items (types, constants & functions)
A-GATs
Area: Generic associated types (GATs)
A-trait-system
Area: Trait system
C-bug
Category: This is a bug.
E-needs-test
Call for participation: An issue has been fixed and does not reproduce, but no test has been added.
F-associated_type_defaults
`#![feature(associated_type_defaults)]`
F-generic_associated_types
`#![feature(generic_associated_types)]` a.k.a. GATs
glacier
ICE tracked in rust-lang/glacier.
I-ICE
Issue: The compiler panicked, giving an Internal Compilation Error (ICE) ❄️
I-unsound
Issue: A soundness hole (worst kind of bug), see: https://en.wikipedia.org/wiki/Soundness
requires-nightly
This issue requires a nightly compiler in some way.
T-compiler
Relevant to the compiler team, which will review and decide on the PR/issue.
Comments
rustbot
added
A-associated-items
steffahn
changed the title
Unimplemented, with associated_type_defaults and generic_associated_typesUnimplemented”, with associated_type_defaults and generic_associated_types
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Okay, this bug allows you to do basically everything. For example
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steffahn
changed the title
Unimplemented”, with associated_type_defaults and generic_associated_types
sfackler
added
the
I-unsound
Here's another one #![feature(generic_associated_types)]
#![feature(associated_type_defaults)]
trait UnsafeCopy {
type Copy<T>: Copy + Drop + ?Sized + std::fmt::Debug = [i32];
fn copy<T: ?Sized>(x: &Self::Copy<T>) {
let blah: Self::Copy<T> = *x;
let b = Box::new(blah);
dbg!(b);
}
}
impl <T> UnsafeCopy for T {}
fn main() {
let b = Box::new([1]) as Box<[i32]>;
let copy = <Box<[i32]>>::copy::<[i32]>(&b);
}ICE's with: |
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Triage: This is no longer ICE with the latest nightly, marking as E-needs-test. |
JohnTitor
added
the
E-needs-test
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(Playground)
Errors:
Removing the
generic_associated_typesmakes this generate appropriate error messages. Seems like combiningassociated_type_defaultsandgeneric_associated_typesis rather uncommon, at least there are no other issues with both labels yet.@rustbot modify labels: I-ICE, T-compiler, requires-nightly, F-associated_type_defaults, F-generic_associated_types, A-traits, A-associated-items, C-bug
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