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Using a reference to a self-referential static as a pattern causes stack overflow #144719

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Using a reference to a self-referential static as a pattern causes stack overflow#144719
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A-const-evalArea: Constant evaluation, covers all const contexts (static, const fn, ...)A-patternsRelating to patterns and pattern matchingC-bugCategory: This is a bug.I-ICEIssue: The compiler panicked, giving an Internal Compilation Error (ICE) ❄️I-crashIssue: The compiler crashes (SIGSEGV, SIGABRT, etc). Use I-ICE instead when the compiler panics.T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.
@theemathas

Description

@theemathas
theemathas
opened on Jul 31, 2025

Code

This code causes rustc to crash with a stack overflow.

#[derive(PartialEq)]
struct Thing(&'static Thing);

static X: Thing = Thing(&X);

const Y: &Thing = &X;

fn main() {
    if let Y = Y {}
}

@rustbot labels +A-const-eval +A-patterns +I-crash

Meta

Reproducible on the playground with stable version 1.88.0.

Error output

error: rustc interrupted by SIGSEGV, printing backtrace
Backtrace 

/playground/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/librustc_driver-277627f6f3b9f29c.so(+0x399a39f)[0x75dba779a39f]
/lib/x86_64-linux-gnu/libc.so.6(+0x45330)[0x75dba3c33330]
/playground/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/librustc_driver-277627f6f3b9f29c.so(+0x5950f0e)[0x75dba9750f0e]
/playground/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/librustc_driver-277627f6f3b9f29c.so(+0x5933fcb)[0x75dba9733fcb]
/playground/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/librustc_driver-277627f6f3b9f29c.so(+0x59349db)[0x75dba97349db]

### cycle encountered after 5 frames with period 6
/playground/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/librustc_driver-277627f6f3b9f29c.so(+0x5934bf7)[0x75dba9734bf7]
/playground/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/librustc_driver-277627f6f3b9f29c.so(+0x592f178)[0x75dba972f178]
/playground/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/librustc_driver-277627f6f3b9f29c.so(+0x5934a27)[0x75dba9734a27]
/playground/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/librustc_driver-277627f6f3b9f29c.so(+0x5934bf7)[0x75dba9734bf7]
/playground/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/librustc_driver-277627f6f3b9f29c.so(+0x592f178)[0x75dba972f178]
/playground/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/librustc_driver-277627f6f3b9f29c.so(+0x5934a27)[0x75dba9734a27]
### recursed 41 times

/playground/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/librustc_driver-277627f6f3b9f29c.so(+0x5934bf7)[0x75dba9734bf7]
/playground/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/librustc_driver-277627f6f3b9f29c.so(+0x592f178)[0x75dba972f178]
/playground/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/librustc_driver-277627f6f3b9f29c.so(+0x5934a27)[0x75dba9734a27]
/playground/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/librustc_driver-277627f6f3b9f29c.so(+0x5934bf7)[0x75dba9734bf7]
/playground/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/librustc_driver-277627f6f3b9f29c.so(+0x592f178)[0x75dba972f178]

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
note: backtrace dumped due to SIGSEGV! resuming signal
error: could not compile `playground` (bin "playground")

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    A-const-evalArea: Constant evaluation, covers all const contexts (static, const fn, ...)A-patternsRelating to patterns and pattern matchingC-bugCategory: This is a bug.I-ICEIssue: The compiler panicked, giving an Internal Compilation Error (ICE) ❄️I-crashIssue: The compiler crashes (SIGSEGV, SIGABRT, etc). Use I-ICE instead when the compiler panics.T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.

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