rust-lang / rust-lang/rust

stack overflow in `rustc_ty_utils::opaque_types::OpaqueTypeCollector as rustc_type_ir::visit::TypeVisitor<rustc_middle::ty::context::TyCtxt>>::visit_ty::{closure#0}`

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A-impl-trait C-bug I-crash T-compiler
Dominant language
Rust
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Description

Code
struct Foo<F: FnOnce(T), F: FnOnce(T)> {
    f: FooImpl,
}

type FooImpl = Foo<FooImpl, impl FnOnce(ImplT)>;

fn bar() -> FooImpl {}

does not seem to be fixed by the new solver

Meta

rustc --version --verbose:

rustc 1.80.0-nightly (faefc618c 2024-05-07)
binary: rustc
commit-hash: faefc618cf48bd794cbc808448df1bf3f59f36af
commit-date: 2024-05-07
host: x86_64-unknown-linux-gnu
release: 1.80.0-nightly
LLVM version: 18.1.4
Error output
<output>
Backtrace

error[E0403]: the name `F` is already used for a generic parameter in this item's generic parameters
 --> ice.rs:1:26
  |
1 | struct Foo<F: FnOnce(T), F: FnOnce(T)> {
  |            -             ^ already used
  |            |
  |            first use of `F`

error[E0412]: cannot find type `T` in this scope
 --> ice.rs:1:22
  |
1 | struct Foo<F: FnOnce(T), F: FnOnce(T)> {
  |                      ^ not found in this scope

error[E0412]: cannot find type `T` in this scope
 --> ice.rs:1:36
  |
1 | struct Foo<F: FnOnce(T), F: FnOnce(T)> {
  |                                    ^ not found in this scope

error[E0412]: cannot find type `ImplT` in this scope
 --> ice.rs:5:41
  |
5 | type FooImpl = Foo<FooImpl, impl FnOnce(ImplT)>;
  |                                         ^^^^^ not found in this scope
  |
help: you might be missing a type parameter
  |
5 | type FooImpl<ImplT> = Foo<FooImpl, impl FnOnce(ImplT)>;
  |             +++++++

error[E0658]: `impl Trait` in type aliases is unstable
 --> ice.rs:5:29
  |
5 | type FooImpl = Foo<FooImpl, impl FnOnce(ImplT)>;
  |                             ^^^^^^^^^^^^^^^^^^
  |
  = note: see issue #63063 <https://github.com/rust-lang/rust/issues/63063> for more information
  = help: add `#![feature(type_alias_impl_trait)]` to the crate attributes to enable
  = note: this compiler was built on 2024-05-07; consider upgrading it if it is out of date

error[E0601]: `main` function not found in crate `ice`
 --> ice.rs:7:23
  |
7 | fn bar() -> FooImpl {}
  |                       ^ consider adding a `main` function to `ice.rs`

error[E0275]: overflow normalizing the type alias `FooImpl`
 --> ice.rs:2:8
  |
2 |     f: FooImpl,
  |        ^^^^^^^
  |
  = note: in case this is a recursive type alias, consider using a struct, enum, or union instead

error[E0275]: overflow normalizing the type alias `FooImpl`
 --> ice.rs:5:16
  |
5 | type FooImpl = Foo<FooImpl, impl FnOnce(ImplT)>;
  |                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = note: in case this is a recursive type alias, consider using a struct, enum, or union instead

error: rustc interrupted by SIGSEGV, printing backtrace

/home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/librustc_driver-baba34ae40c356f7.so(+0x30d8ca6)[0x7f697f2d8ca6]
/usr/lib/libc.so.6(+0x40770)[0x7f697c05a770]
/home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/librustc_driver-baba34ae40c356f7.so(+0x489a5bc)[0x7f6980a9a5bc]

### cycle encountered after 3 frames with period 4
/home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/librustc_driver-baba34ae40c356f7.so(+0x489a60d)[0x7f6980a9a60d]
/home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/librustc_driver-baba34ae40c356f7.so(+0x489b76f)[0x7f6980a9b76f]
/home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/librustc_driver-baba34ae40c356f7.so(+0x489a60d)[0x7f6980a9a60d]
/home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/librustc_driver-baba34ae40c356f7.so(+0x489b76f)[0x7f6980a9b76f]
### recursed 63 times

/home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/librustc_driver-baba34ae40c356f7.so(+0x489a60d)[0x7f6980a9a60d]

note: rustc unexpectedly overflowed its stack! this is a bug
note: maximum backtrace depth reached, frames may have been lost
note: we would appreciate a report at https://github.com/rust-lang/rust
help: you can increase rustc's stack size by setting RUST_MIN_STACK=16777216
[1]    135140 segmentation fault  rustc ice.rs

Contributor guide

Open the contributing guide

First steps

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  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start by reproducing the crash with the provided ice.rs example on the reported nightly toolchain. Trace the rustc_ty_utils::opaque_types::OpaqueTypeCollector visitor named in the title and compare behavior with the new solver. Done means the example no longer overflows rustc's stack or segfaults, with a regression test covering the failure.

Written by the indexing model from the issue text.

Assessment

Tech stack
rust
Domain
compilers
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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