rustc hangs in trait solver due to infinite recursion in generic tuple implementation

I tried this code:

trait MutableBinding {}
impl<T> MutableBinding for T
where
    (W, T, W, T): MutableBinding,
{}
impl<
    T: ,
    U: ,
    V: ,
    W: MutableBinding,
> MutableBinding for (T, U, V, W) {}
fn main(){}

I expected to see this happen: The compiler should report an error (e.g. recursion limit reached or undefined type W) instead of hanging.

Instead, this happened: The compiler enters an infinite loop (hangs) during trait resolution . both in next solver and new solver.

Meta

rustc --version --verbose:

rustc 1.93.0 (254b59607 2026-01-19)
binary: rustc
commit-hash: 254b59607d4417e9dffbc307138ae5c86280fe4c
commit-date: 2026-01-19
host: x86_64-unknown-linux-gnu
release: 1.93.0
LLVM version: 21.1.8

<backtrace>

Start by compiling the supplied reproducer with rustc 1.93.0 and tracing the trait-resolution path in both the next and new solvers, where the report says the hang occurs. Done means the compiler terminates with a diagnostic such as a recursion-limit or undefined-type error rather than looping.