rustc flags the wrong line for an ambiguous `.into`

[mutexlox-signal]

Code

struct Foo {
    f: Option<i32>,
}
fn main() {
    let v = vec![Foo { f: Some(1) }];
    if let Some(x) = v.get(0_i16.into()) {
        if let Some(f) = x.f {
            println!("{}", f);
        } else {
            println!("not present");
        }
    } else {
        println!("bad index");
    }
}

Current output

error[E0282]: type annotations needed
 --> src/main.rs:7:26
  |
7 |         if let Some(f) = x.f {
  |                          ^^^ cannot infer type

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

Desired output

if let Some(x) = v.get(0_i16.into()) {
                              ---- type must be known at this point

Rationale and extra context

Changing the .into() into an as usize makes the code compile; see https://play.rust-lang.org/?version=nightly&mode=debug&edition=2024&gist=495a6978e412895bf96d37d20efa8697

The access to x.f is not the root cause of the problem, and should not be flagged as such.

Other cases

Rust Version

1.91.0-nightly (2025-09-01 7aef4bec4bec16cb6204)

reproduces on playground and locally:

rustc 1.89.0 (29483883e 2025-08-04)
binary: rustc
commit-hash: 29483883eed69d5fb4db01964cdf2af4d86e9cb2
commit-date: 2025-08-04
host: aarch64-apple-darwin
release: 1.89.0
LLVM version: 20.1.7

Anything else?

No response