False-Positive `non-exhaustive pattern` when `Infallible` is a trait bound and wrapped in certain types

[urben1680]

The new stable Rust feature to use Ok(ok) = infallible_result; is great, though I noticed that rust-analyzer does not always work along it.

I found two ways to wrap the error and cause this issue but there may be more.

---

rust-analyzer version:

• extension release version 0.3.2146-standalone (d7628c0a8 2024-10-12)
• extension pre-release version 0.4.2149-standalone (a439ed8b8 2024-10-16)

rustc version: 1.82.0 (f6e511eec 2024-10-15) stable

editor or extension: VSCode

relevant settings: -

repository link (if public, optional): -

code snippet to reproduce:

This code compiles but rust-analyzer detects non-exhaustive pattern for the latter two functions:

use std::convert::Infallible;

trait Foo {
    type Bar;
}

struct Wrapper<T> {
    error: T,
}

struct FooWrapper<T: Foo> {
    error: T::Bar,
}

// these three work

fn works1<T: Foo<Bar = Infallible>>(result: Result<T, T::Bar>) -> T {
    let Ok(ok) = result;
    ok
}
fn works2<T: Foo<Bar = Infallible>>(result: Result<T, (T::Bar,)>) -> T {
    let Ok(ok) = result;
    ok
}
fn works3<T: Foo<Bar = Infallible>>(result: Result<T, Wrapper<T::Bar>>) -> T {
    let Ok(ok) = result;
    ok
}

// these two do not

fn fails1<T: Foo<Bar = Infallible>>(result: Result<T, FooWrapper<T>>) -> T {
    let Ok(ok) = result;
    ok
}
fn fails2<T: Foo<Bar = Infallible>>(result: Result<T, [T::Bar; 1]>) -> T {
    let Ok(ok) = result;
    ok
}