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Hang on TAIT with diverging projection in its ParamEnv #132797
Description
I tried this code:
rustc file.rs#![feature(type_alias_impl_trait)]
trait Id {
type Assoc;
}
impl<T> *const u8 {
type Assoc = T;
}
type Ty
where
Ty: Id<Assoc = Ty>,
= impl Sized;
fn define() -> Ty {}
fn main() {}This file causes rustc to hang and is derived from mutant #109387. #109387 can terminate successfully.
Meta
rustc --version --verbose:
rustc 1.84.0-nightly (b91a3a056 2024-11-07)
binary: rustc
commit-hash: b91a3a05609a46f73d23e0995ae7ebb4a4f429a5
commit-date: 2024-11-07
host: x86_64-unknown-linux-gnu
release: 1.84.0-nightly
LLVM version: 19.1.3
Compiler Output (before the hang)
error[E0658]: inherent associated types are unstable
--> file.rs:6:5
|
6 | type Assoc = T;
| ^^^^^^^^^^^^^^^
|
= note: see issue #8995 <https://github.com/rust-lang/rust/issues/8995> for more information
= help: add `#![feature(inherent_associated_types)]` to the crate attributes to enable
= note: this compiler was built on 2024-11-04; consider upgrading it if it is out of date
error[E0207]: the type parameter `T` is not constrained by the impl trait, self type, or predicates
--> file.rs:5:6
|
5 | impl<T> *const u8 {
| ^ unconstrained type parameter
error[E0277]: the trait bound `Ty: Id` is not satisfied
--> file.rs:8:1
|
8 | type Ty
| ^^^^^^^ the trait `Id` is not implemented for `Ty`
|
help: this trait has no implementations, consider adding one
--> file.rs:2:1
|
2 | trait Id {
| ^^^^^^^^
note: required by a bound on the type alias `Ty`
--> file.rs:10:9
|
10 | Ty: Id<Assoc = Ty>,
| ^^^^^^^^^^^^^^ required by this bound
error[E0277]: the trait bound `Ty: Id` is not satisfied
--> file.rs:10:5
|
10 | Ty: Id<Assoc = Ty>,
| ^^^^^^^^^^^^^^^^^^ the trait `Id` is not implemented for `Ty`
|
help: this trait has no implementations, consider adding one
--> file.rs:2:1
|
2 | trait Id {
| ^^^^^^^^
= help: see issue #48214
help: add `#![feature(trivial_bounds)]` to the crate attributes to enable
|
2 + #![feature(trivial_bounds)]
|
error[E0277]: the trait bound `Ty: Id` is not satisfied
--> file.rs:11:3
|
11 | = impl Sized;
| ^^^^^^^^^^ the trait `Id` is not implemented for `Ty`
|
help: this trait has no implementations, consider adding one
--> file.rs:2:1
|
2 | trait Id {
| ^^^^^^^^
note: required by a bound on the type alias `Ty`
--> file.rs:10:9
|
10 | Ty: Id<Assoc = Ty>,
| ^^^^^^^^^^^^^^ required by this bound
error[E0277]: the trait bound `Ty: Id` is not satisfied
--> file.rs:12:16
|
12 | fn define() -> Ty {}
| ^^ the trait `Id` is not implemented for `Ty`
|
help: this trait has no implementations, consider adding one
--> file.rs:2:1
|
2 | trait Id {
| ^^^^^^^^
note: required by a bound on the type alias `Ty`
--> file.rs:10:9
|
10 | Ty: Id<Assoc = Ty>,
| ^^^^^^^^^^^^^^ required by this bound
error[E0277]: the trait bound `Ty: Id` is not satisfied
--> file.rs:12:19
|
12 | fn define() -> Ty {}
| ^^ the trait `Id` is not implemented for `Ty`
|
help: this trait has no implementations, consider adding one
--> file.rs:2:1
|
2 | trait Id {
| ^^^^^^^^
note: required by a bound on the type alias `Ty`
--> file.rs:10:9
|
10 | Ty: Id<Assoc = Ty>,
| ^^^^^^^^^^^^^^ required by this bound
error[E0390]: cannot define inherent `impl` for primitive types
--> file.rs:5:1
|
5 | impl<T> *const u8 {
| ^^^^^^^^^^^^^^^^^
|
= help: consider using an extension trait instead
Activity
kadenlnelson commentedon Nov 9, 2024
How long does it hang for? Are you able to provide a profile that shows where the time is being spent?
If you may as well, provide the full output that is shown when you execute
rustc.ym-xie commentedon Nov 9, 2024
I used the command
timeout 60 rustc file.rs, and when it timed out, the partial output was as follows:fmease commentedon Nov 10, 2024
The IAT (inherent associated type) isn't needed; the hang also occurs without it:
I'd also like to note the extreme growth in memory use apart from the hang (e.g., I'm getting jumps from roughly 6GiB (baseline) to 9GiB to 12GiB RAM use).
[-]Hang: type_alias_impl_trait[/-][+]Hang on TAIT with diverging projection in its ParamEnv[/+]