1.100 beta regression: ICE with "has escaping bound vars, so it cannot be wrapped in a dummy binder"

This regression was discovered in the 1.100 beta --release crater run. However, it does reproduce locally with just cargo +beta check.

There were multiple ICEs raised in a row. Below is the first one:

[INFO] [stderr] thread 'rustc' (3831) panicked at /rustc-dev/e3feeb59cd1bdd011a2bfcc0747b55125d9b8527/compiler/rustc_middle/src/ty/predicate.rs:490:9:
[INFO] [stderr] `<std::vec::Vec<_> as api::auth::_::_serde::Deserialize<'de>>` has escaping bound vars, so it cannot be wrapped in a dummy binder.

https://crater-reports.s3.amazonaws.com/beta-release-1.100/1.100.0-beta.1%2Bcargoflags=--release/gh/gefo10.deutsch_fluent_frontend/log.txt

Note that the code doesn't compile on 1.99. The following is the log for that: https://crater-reports.s3.amazonaws.com/beta-release-1.100/1.99.0-beta.8%2Bcargoflags=--release/gh/gefo10.deutsch_fluent_frontend/log.txt

minimized:

#[derive(Clone)]
struct S<'a, T>(&'a T);

fn require<T>() where for<'a> S<'a, T>: Clone {}

fn main() {
    require::<&'static mut u8>();
}

bisection:

searched nightlies: from nightly-2026-08-25 to nightly-2026-09-05
regressed nightly: nightly-2026-08-31
searched commit range: fd7ed57...9085017
regressed commit: d0ea9cd

bisected with cargo-bisect-rustc v0.6.11

Host triple: aarch64-apple-darwin
Reproduce with:

cargo bisect-rustc --start 2026-08-25 --end 2026-09-05 --regress=ice --timeout 10 --preserve-target

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1.100 beta regression: ICE with "has escaping bound vars, so it cannot be wrapped in a dummy binder" #164376

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1.100 beta regression: ICE with "has escaping bound vars, so it cannot be wrapped in a dummy binder" #164376

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sjwang05 commented on Oct 15, 2026

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