Never type doesn't coerce within type paramaters

I tried this code:

fn consume(_: Result<(), ()>) {}

fn type_err() {
    let t: Result<!, ()> = Result::Err(());
    consume(t)
}

I expected to see this happen: it compiles, since if you have a Result<!, ()> you vacuously have a Result<T, ()>

Instead, this happened:

error[E0308]: mismatched types
 --> src/main.rs:5:13
  |
5 |     consume(t)
  |     ------- ^ expected `Result<(), ()>`, found `Result<!, ()>`
  |     |
  |     arguments to this function are incorrect
  |
  = note: expected enum `Result<(), _>`
             found enum `Result<!, _>`
note: function defined here
 --> src/main.rs:1:4
  |
1 | fn consume(_: Result<(), ()>) {}
  |    ^^^^^^^ -----------------

I guess the problem is that the Result<!, ()> is sized early, which limits its ability to coerce into other (potentially larger) types.

The motivating example was being able to call functions which return Result<...> in a function which returns ControlFlow<Result<...>>:

#![feature(try_trait_v2)]

use std::ops::{ControlFlow, Try};

fn maybe_fails() -> Result<(), ()> {
    Err(())
}

fn motivating_example() -> ControlFlow<Result<(), ()>> {
    maybe_fails().branch()?; // fails because we can't coerce Result<!, ()> into Result<(), ()>
    ControlFlow::Break(Ok(()))
}

Meta

rustc --version --verbose:

rustc 1.100.0-nightly (4aa1fbcf4 2026-09-08)
binary: rustc
commit-hash: 4aa1fbcf467cf38ce58abfa8eb9213a789c5381c
commit-date: 2026-09-08
host: x86_64-unknown-linux-gnu
release: 1.100.0-nightly
LLVM version: 23.1.1

<backtrace>

Start by running the Result<!, ()> reproducer in src/main.rs with the reported nightly toolchain, then compare it with the ControlFlow<Result<(), ()>> motivating example. Read the compiler's handling of never-type coercions within generic type parameters. Done means the shown calls compile with the expected coercion, with regression coverage for both examples.