rust-lang / rust-lang/rust

[ICE]: assumptions-on-binders: stack overflow

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-Zassumptions-on-binders C-bug I-crash needs-triage T-compiler
Dominant language
Rust
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Description

Code

rustc -Zassumptions-on-binders file.rs

fn foo<'a>(
    d: impl Sized + 'a,
    p: &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&'a(),
) -> impl Sized + 'a {
    (d, p)
}

fn main() {}
Meta

rustc --version --verbose:

rustc 1.100.0-nightly (b0ca9c712 2026-08-22)
binary: rustc
commit-hash: b0ca9c712455d865c3bf0bf5325a3e79677a2d97
commit-date: 2026-08-22
host: x86_64-unknown-linux-gnu
release: 1.100.0-nightly
LLVM version: 23.1.0
Error output

Backtrace

error: rustc interrupted by SIGSEGV, printing backtrace

/home/matthias/.rustup/toolchains/master/bin/../lib/librustc_driver-e93a2dba77124397.so(+0x3faed7c) [0x7fd2d29aed7c]
/usr/lib/libc.so.6(+0x3e270) [0x7fd2ce63e270]
/home/matthias/.rustup/toolchains/master/bin/../lib/librustc_driver-e93a2dba77124397.so(+0x4d3fb8c) [0x7fd2d373fb8c]

### cycle encountered after 3 frames with period 4
/home/matthias/.rustup/toolchains/master/bin/../lib/librustc_driver-e93a2dba77124397.so(+0x4d3fb91) [0x7fd2d373fb91]
/home/matthias/.rustup/toolchains/master/bin/../lib/librustc_driver-e93a2dba77124397.so(+0x4d3fb91) [0x7fd2d373fb91]
/home/matthias/.rustup/toolchains/master/bin/../lib/librustc_driver-e93a2dba77124397.so(+0x4d3fb91) [0x7fd2d373fb91]
/home/matthias/.rustup/toolchains/master/bin/../lib/librustc_driver-e93a2dba77124397.so(+0x4d3fb91) [0x7fd2d373fb91]
### recursed 63 times

/home/matthias/.rustup/toolchains/master/bin/../lib/librustc_driver-e93a2dba77124397.so(+0x4d3fb91) [0x7fd2d373fb91]

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=33554432
[1]    3792664 segmentation fault  ~/.rustup/toolchains/master/bin/rustc -Zassumptions-on-binders a.rs

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  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 from file.rs with rustc -Zassumptions-on-binders and the provided example, then use the reported stack-overflow backtrace to locate the compiler path involved. Done means this input no longer overflows rustc's stack and the relevant compiler test coverage verifies the behavior.

Written by the indexing model from the issue text.

Assessment

Tech stack
rust
Domain
compilers
Issue type
Bug
Difficulty
5/5
Estimated time
Over a week
Activity status
Active
Clarity
Mostly clear
Newbie friendliness
25/100

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