[ER] Better than the "unresolved import `super::K`" error message

[leonardo-m]

Code

For wrong code like this:


fn foo() {
    const K: usize = 1;

    mod inner {
        use super::K;

        fn bar() {
            dbg!(K);
        }
    }
}
fn main() {}

Current output

rustc 1.88.0-nightly (25cdf1f67 2025-04-28) currently gives:


error[E0432]: unresolved import `super::K`
 --> ...\test.rs:5:13
  |
5 |         use super::K;
  |             ^^^^^^^^ no `K` in the root

error: aborting due to 1 previous error

Desired output

But I'd like an error message that tries to suggest how to correctly import the name X.

Rationale and extra context

No response

Other cases

Rust Version

rustc 1.88.0-nightly (25cdf1f67 2025-04-28)
binary: rustc
commit-hash: 25cdf1f67463c9365d8d83778c933ec7480e940b
commit-date: 2025-04-28
host: x86_64-pc-windows-gnu
release: 1.88.0-nightly
LLVM version: 20.1.2

Anything else?

No response

[Urgau]

But I'd like an error message that tries to suggest how to correctly import the name X.

I can think of multiple "suggestion", but they are all invasive, which would you like rustc to suggest?

• Move const K: usize = 1; out-side the function
• Remove the intermediate mod inner
• Pass K as a parameter

In any case we should note that items defined inside a function are local to that function and are not accessible from nested modules.

[leonardo-m]

In any case we should note that items defined inside a function are local to that function and are not accessible from nested modules.<

I agree, that's the basic improvement, it could be enough.

But can't we offer a way to access the items defined inside functions from modules defined inside them? :-)

which would you like rustc to suggest?<

Perhaps none of them.

[xizheyin]

note that items defined inside a function are local to that function and are not accessible from nested modules.

I don't know if the compiler can detect that K is defined inside the function foo, if it can it can give note in the diagnostics.
If can not, where would be a better place to do this prompt, perhaps in the documentation for E0432?