"E0432 unresolved import" on the same line should emit one diagnostic

[estebank]

Currently when writing use foo::{bar, baz, qux} when foo exists but none of bar, baz and qux do, we emit one diagnostic per unresolved import. We should collect these onto a single multispan error.

[PramodBisht]

@estebank I would like to take this on if you are not planning to solve it yourself. It may take me sometime to solve it though. BTW, how you are planning to show the diagnostic message.

[estebank]

I would like to take this on if you are not planning to solve it yourself.

Go ahead!

It may take me sometime to solve it though.

That it's fine.

BTW, how you are planning to show the diagnostic message.

My thinking is that it should look similar to what it already does. The approach I'd take would be to just collect all of the unresolved imports for a single use statement in a vector and then emit an error using the spans of those turned into a MultiSpan, and adding a span label for each one of them that reads the same as it currently does.

[PramodBisht]

@estebank I have created a basic structure to fix the issue, now I am stuck in a situation where I need to show help like did you mean ...? How I should display that?

[PramodBisht]

Now this type of output we are getting

error[E0432]: unresolved imports: `std::time::foo`, `std::time::bar`, `std::time::buzz`, `std::time::abc`, `std::time::def`
 --> /tmp/test.rs:1:17
  |
1 | use std::time::{foo, bar, buzz};
  |                 ^^^  ^^^  ^^^^
2 | use std::time::{abc, def};
  |                 ^^^  ^^^

warning: unused imports: `bar`, `buzz`, `foo`
 --> /tmp/test.rs:1:17
  |
1 | use std::time::{foo, bar, buzz};
  |                 ^^^  ^^^  ^^^^
  |
  = note: #[warn(unused_imports)] on by default

warning: unused imports: `abc`, `def`
 --> /tmp/test.rs:2:17
  |
2 | use std::time::{abc, def};
  |                 ^^^  ^^^

error: aborting due to previous error

For more information about this error, try `rustc --explain E0432`.

instead of

error[E0432]: unresolved import `std::time::foo`
 --> /tmp/test.rs:1:17
  |
1 | use std::time::{foo, bar, buzz};
  |                 ^^^ no `foo` in `time`

error[E0432]: unresolved import `std::time::bar`
 --> /tmp/test.rs:1:22
  |
1 | use std::time::{foo, bar, buzz};
  |                      ^^^ no `bar` in `time`

error[E0432]: unresolved import `std::time::buzz`
 --> /tmp/test.rs:1:27
  |
1 | use std::time::{foo, bar, buzz};
  |                           ^^^^ no `buzz` in `time`

error[E0432]: unresolved import `std::time::abc`
 --> /tmp/test.rs:2:17
  |
2 | use std::time::{abc, def};
  |                 ^^^ no `abc` in `time`

error[E0432]: unresolved import `std::time::def`
 --> /tmp/test.rs:2:22
  |
2 | use std::time::{abc, def};
  |                      ^^^ no `def` in `time`

warning: unused imports: `bar`, `buzz`, `foo`
 --> /tmp/test.rs:1:17
  |
1 | use std::time::{foo, bar, buzz};
  |                 ^^^  ^^^  ^^^^
  |
  = note: #[warn(unused_imports)] on by default

warning: unused imports: `abc`, `def`
 --> /tmp/test.rs:2:17
  |
2 | use std::time::{abc, def};
  |                 ^^^  ^^^

error: aborting due to 5 previous errors

For more information about this error, try `rustc --explain E0432`.