Account for item-local, out of scope bindings, in E0425

[estebank]

When encountering a binding that is not available

     let foo = 1;
    {
        let bar = 2;
    }
    println!("{foo} {bar}");

the error should mention bindings that are outside of the scope but within the same item

error[E0425]: cannot find value `bar` in this scope
 --> src/main.rs:6:22
  |
6 |     println!("{foo} {bar}");
  |                      ^^^ not found in this scope
note: the binding `bar` is available in a different scope in the same function
 --> src/main.rs:4:8
  |
4 |         let bar = 2;
  |             ^^^

[chenyukang]

@rustbot claim

[chenyukang]

Do you think we should suggest in this scenario?

#![feature(if_let_guard)]

fn main() {
    match Some(None) {
        Some(x) if let Some(y) = x => (x, y),
        _ => y, //~ ERROR cannot find value `y`
    }
    y //~ ERROR cannot find value `y`
}

My local dev branch will suggest:

error[E0425]: cannot find value `y` in this scope
 --> src/test/ui/rfc-2294-if-let-guard/bindings.rs:6:14
  |
6 |         _ => y, //~ ERROR cannot find value `y`
  |              ^
  |
help: the binding `y` is available in a different scope in the same function
 --> src/test/ui/rfc-2294-if-let-guard/bindings.rs:5:29
  |
5 |         Some(x) if let Some(y) = x => (x, y),
  |                             ^

error[E0425]: cannot find value `y` in this scope
 --> src/test/ui/rfc-2294-if-let-guard/bindings.rs:8:5
  |
8 |     y //~ ERROR cannot find value `y`
  |     ^ not found in this scope

error: aborting due to 2 previous errors

[chenyukang]

I removed it.