`type annotations needed` for `if let Some(whatever) = todo!() {` not very helpful

Code

fn main() {
    if let Some(whatever) = todo!() {
        todo!();
    } else {
        todo!();
    }
}

Current output

error[E0282]: type annotations needed
 --> src/main.rs:2:17
  |
2 |     if let Some(whatever) = todo!() {
  |                 ^^^^^^^^ cannot infer type

For more information about this error, try `rustc --explain E0282`.

It's not really clear how rustc would like to see the type annotations, without adding an extra binding and without type_ascription

What does not work:

if let Some(whatever): Option<i32> = todo!() {
or
if let Some(whatever: i32) = todo!() {

what did end up working:

if let Some(x) = Some(todo!()) {
or
if let Some(x @ ()) = todo!() {

zulip thread: https://rust-lang.zulipchat.com/#narrow/channel/147480-t-compiler.2Fdiagnostics/topic/type.20annotations.20needed.20.60if.20let.20Some.28x.29.20.3D.20todo!.28.29.60/with/521126024

Rust Version

rustc 1.89.0-nightly (6f6971078 2025-05-28)
binary: rustc
commit-hash: 6f69710780d579b180ab38da4c1384d630f7bd31
commit-date: 2025-05-28
host: x86_64-unknown-linux-gnu
release: 1.89.0-nightly
LLVM version: 20.1.5

Start by reproducing the supplied Rust example with the noted nightly version and compare the current E0282 diagnostic with the issue's working alternatives. Trace the compiler diagnostic path that reports “cannot infer type”; done means the error explains how to provide a useful annotation for this pattern without requiring an extra binding.