Code change:
<ins> error[E0261]: use of undeclared lifetime name `'a` --> $DIR/ice-unexpected-inference-var-122549.rs:5:70 | LL |     fn const_chunks_exact<const N: usize>(&self) -> ConstChunksExact<'a, T, { N }>; |                                                                      ^^ undeclared lifetime | help: consider introducing lifetime `'a` here | LL |     fn const_chunks_exact<'a, const N: usize>(&self) -> ConstChunksExact<'a, T, { N }>; |                           +++ help: consider introducing lifetime `'a` here | LL | trait ConstChunksExactTrait<'a, T> { |                             +++ error[E0261]: use of undeclared lifetime name `'a` --> $DIR/ice-unexpected-inference-var-122549.rs:11:34 | LL | struct ConstChunksExact<'rem, T: 'a, const N: usize> {} |                         -        ^^ undeclared lifetime |                         | |                         help: consider introducing lifetime `'a` here: `'a,` error[E0046]: not all trait items implemented, missing: `const_chunks_exact` --> $DIR/ice-unexpected-inference-var-122549.rs:9:1 | LL |     fn const_chunks_exact<const N: usize>(&self) -> ConstChunksExact<'a, T, { N }>; |     ------------------------------------------------------------------------------- `const_chunks_exact` from trait ... LL | impl<T> ConstChunksExactTrait<T> for [T] {} | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ missing `const_chunks_exact` in implementation error[E0392]: lifetime parameter `'rem` is never used --> $DIR/ice-unexpected-inference-var-122549.rs:11:25 | LL | struct ConstChunksExact<'rem, T: 'a, const N: usize> {} |                         ^^^^ unused lifetime parameter | = help: consider removing `'rem`, referring to it in a field, or using a marker such as `PhantomData` error[E0392]: type parameter `T` is never used --> $DIR/ice-unexpected-inference-var-122549.rs:11:31 | LL | struct ConstChunksExact<'rem, T: 'a, const N: usize> {} |                               ^ unused type parameter | = help: consider removing `T`, referring to it in a field, or using a marker such as `PhantomData` error[E0207]: the const parameter `N` is not constrained by the impl trait, self type, or predicates --> $DIR/ice-unexpected-inference-var-122549.rs:15:13 | LL | impl<'a, T, const N: usize> Iterator for ConstChunksExact<'a, T, {}> { |             ^^^^^^^^^^^^^^ unconstrained const parameter | = note: expressions using a const parameter must map each value to a distinct output value = note: proving the result of expressions other than the parameter are unique is not supported error[E0308]: mismatched types --> $DIR/ice-unexpected-inference-var-122549.rs:15:66 | LL | impl<'a, T, const N: usize> Iterator for ConstChunksExact<'a, T, {}> { |                                                                  ^^ expected `usize`, found `()` error: aborting due to 7 previous errors Some errors have detailed explanations: E0046, E0207, E0261, E0308, E0392. For more information about an error, try `rustc --explain E0046`. </ins>

Related discussion:
text: rustcspan[]::ErrorGuaranteed33: 0x7ff806223632 - <<std[]::thread::Builder::spawnunchecked<rustcinterface[]::util::runinthreadwithglobals<rustcinterface[]::util::runinthreadpoolwithglobals<rustcinterface[]::interface::runcompiler<core[]::result::Result<(), rustcspan[]::ErrorGuaranteed, rustcdriverimpl[]::runcompiler::{closure}::{closure}, core[]::result::Result<(), rustcspan[]::ErrorGuaranteed::{closure}, core[]::result::Result<(), rustcspan[]::ErrorGuaranteed::{closure}::{closure}, core[]::result::Result<(), rustcspan[]::ErrorGuaranteed::{closure} as core[]::ops::function::FnOnce<()::callonce::{shim:vtable} 34: 0x7ff8073b11e5 - <alloc::boxed::Box<F,Aas core::ops::function::FnOnce<Args::callonce::hab5d072bb143d8fe at 35: 0x7ff8073b11e5 - <alloc::boxed::Box<F,Aas core::ops::function::FnOnce<Args::callonce::he1f566ad483a8fda at 36: 0x7ff8073b11e5 - std::sys::pal::unix::thread::Thread::new::threadstart::h23d47a8da771b95c at 37: 0x7ff800ea955a - <unknown38: 0x7ff800f26a3c - <unknown39: 0x0 - <unknownerror: the compiler unexpectedly panicked. this is a bug. note: we would appreciate a bug report: note: rustc 1.78.0-nightly ( 2024-03-15) running on x8664-unknown-linux-gnu query stack during panic: [mirborrowck] borrow-checking [analysis] running analysis passes on this crate end of query stack error: aborting due to 7 previous errors Some errors have detailed explanations: E0046, E0207, E0261, E0308, E0392. For more information about an error, try .