Removes suggestions for misspelled private fields for structs defined in non-local crates

[leejunseok]

closes #22421

[rust-highfive]

r? @nikomatsakis

(rust_highfive has picked a reviewer for you, use r? to override)

[ghost]

@leejunseok Looking good, thank you!

Could you please also add a test for the new behaviour? It's not hard to do! You'll need to create an auxiliary compile-fail test in src/test/compile-fail.

// aux-build:struct-field-privacy.rs

extern crate struct-field-privacy;

use struct-field-privacy::A;

fn main () {
    // ...
}

struct-field-privacy.rs will then act as your external create. struct-field-hints.rs is an example of what you will need to put in in place of // ... to assert what field hints the compiler should provide.

[leejunseok]

Er, it looks like the dashes in struct-field-privacy trips everything up. Is there another external crate I could use instead?

[leejunseok]

Oops, just kidding, doing extern crate "struct-field-privacy" as xc; seems to work.

[ghost]

@leejunseok My bad, you'll need a license header for the test as well! With that r=me. :)

[leejunseok]

Haha, thank you for your help. I'm relatively new to rust and I appreciate the friendly guidance!

[leejunseok]

r? @jakub-

[ghost]

@bors: r+ c87b722

[ghost]

@leejunseok No probs! Thanks again. :)

[ghost]

@bors: r+ 9b67d07

[bors]

⌛ Testing commit 9b67d07 with merge 9abf514...

[bors]

💔 Test failed - auto-linux-32-nopt-t

[Manishearth]

The failure above was triggered by me; this PR is part of the rollup so it's redundant to test it individually (and given the state of the queue, rather wasteful). If the rollup doesn't go through in a couple of tries, ask for a retry on this 😄

Sorry for the trouble!