Compiler hangs during execution #139197
Description
I tried this code:
trait Trait {} struct W<T>(T); impl<T, U> Trait for W<(<&Self as IntoIterator>, W<U>)> where W<T>: Trait, W<U>: Trait, { } fn impls<T: Trait>() {} fn main() { impls::<W<_>>(); }I expected to see this happen:
The compilation process should complete successfully, and any errors in the code should be reported with diagnostic messages.
Instead, this happened:
The compiler hangs indefinitely and appears to never terminate.
Meta
rustc --version --verbose:
rustc 1.85.1 (4eb161250 2025-03-15) binary: rustc commit-hash: 4eb161250e340c8f48f66e2b929ef4a5bed7c181 commit-date: 2025-03-15 host: x86_64-pc-windows-msvc release: 1.85.1 LLVM version: 19.1.7 Backtrace
error: expected `::`, found `,` --> .\temp.rs:7:48 | 7 | impl<T, U> Trait for W<(<&Self as IntoIterator>, W<U>)> | ^ expected `::` error: expected `::`, found `,` --> .\temp.rs:7:48 | 7 | impl<T, U> Trait for W<(<&Self as IntoIterator>, W<U>)> | ^ expected `::` | help: expressions must be enclosed in braces to be used as const generic arguments | 7 | impl<T, U> Trait for W<{ (<&Self as IntoIterator>, W<U>) }> | + + error[E0747]: constant provided when a type was expected --> .\temp.rs:7:24 | 7 | impl<T, U> Trait for W<(<&Self as IntoIterator>, W<U>)> | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^