rust-lang / rust-lang/rust

rustc should magically detect repeating refactoring errors and compress them

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Description

This error report is now live as a repo:

https://github.com/workingjubilee/uwu-er-i-mean-owo

Code

If you have code that looks like this:

#[macro_use]
macro_rules! uwuify {
    ($($this:ident),*) => {
        $(
        impl WhatsThis for $this {
            fn uwu() -> Self {
                <$this as Default>::default()
            }
        }
        )*
    }
}
mod ty0;
mod ty1;
mod ty2;
mod ty3;
mod ty4;
mod ty5;
mod ty6;
mod ty7;
mod ty8;
mod ty9;

trait WhatsThis {
    fn uwu() -> Self;
}

impl WhatsThis for SomeType {
    fn uwu() -> Self {
        SomeType::less_trivial_constructor(SOME_CONSTANT)
    }
}

Where each mod has some contents like this:

#[derive(Default)]
pub struct Ty0 {}

uwuify!(Ty0);

Then change the code this way:

 trait WhatsThis {
-    fn uwu() -> Self;
+    fn owo() -> Self;
 }
 
 impl WhatsThis for SomeType {
-    fn uwu() -> Self {
+    fn owo() -> Self {
         SomeType::less_trivial_constructor(SOME_CONSTANT)
     }
 }

The problem here is that I forgot to rename the items in the macro appropriately, and this is frequently missed by the way rust-analyzer's bulk-refactoring is integrated in at least some editors. We now get this error:

Current output
$ cargo check
    Checking whats-this v0.1.0 (/home/jubilee/rust/whats-this)
error[E0407]: method `uwu` is not a member of trait `WhatsThis`
  --> src/main.rs:14:13
   |
14 | /             fn uwu() -> Self {
15 | |                 <$this as Default>::default()
16 | |             }
   | |_____________^ not a member of trait `WhatsThis`
   |
  ::: src/ty0.rs:4:1
   |
4  | / uwuify
5  | | !
6  | | (Ty0);
   | |_____- in this macro invocation
   |
   = note: this error originates in the macro `uwuify` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0407]: method `uwu` is not a member of trait `WhatsThis`
  --> src/main.rs:14:13
   |
14 | /             fn uwu() -> Self {
15 | |                 <$this as Default>::default()
16 | |             }
   | |_____________^ not a member of trait `WhatsThis`
   |
  ::: src/ty1.rs:4:1
   |
4  | / uwuify
5  | | !
6  | | (Ty1);
   | |_____- in this macro invocation
   |
   = note: this error originates in the macro `uwuify` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0407]: method `uwu` is not a member of trait `WhatsThis`
  --> src/main.rs:14:13
   |
14 | /             fn uwu() -> Self {
15 | |                 <$this as Default>::default()
16 | |             }
   | |_____________^ not a member of trait `WhatsThis`
   |
  ::: src/ty2.rs:4:1
   |
4  | / uwuify
5  | | !
6  | | (Ty2);
   | |_____- in this macro invocation
   |
   = note: this error originates in the macro `uwuify` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0407]: method `uwu` is not a member of trait `WhatsThis`
  --> src/main.rs:14:13
   |
14 | /             fn uwu() -> Self {
15 | |                 <$this as Default>::default()
16 | |             }
   | |_____________^ not a member of trait `WhatsThis`
   |
  ::: src/ty3.rs:4:1
   |
4  | / uwuify
5  | | !
6  | | (Ty3);
   | |_____- in this macro invocation
   |
   = note: this error originates in the macro `uwuify` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0407]: method `uwu` is not a member of trait `WhatsThis`
  --> src/main.rs:14:13
   |
14 | /             fn uwu() -> Self {
15 | |                 <$this as Default>::default()
16 | |             }
   | |_____________^ not a member of trait `WhatsThis`
   |
  ::: src/ty4.rs:4:1
   |
4  | / uwuify
5  | | !
6  | | (Ty4);
   | |_____- in this macro invocation
   |
   = note: this error originates in the macro `uwuify` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0407]: method `uwu` is not a member of trait `WhatsThis`
  --> src/main.rs:14:13
   |
14 | /             fn uwu() -> Self {
15 | |                 <$this as Default>::default()
16 | |             }
   | |_____________^ not a member of trait `WhatsThis`
   |
  ::: src/ty5.rs:4:1
   |
4  | / uwuify
5  | | !
6  | | (Ty5);
   | |_____- in this macro invocation
   |
   = note: this error originates in the macro `uwuify` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0407]: method `uwu` is not a member of trait `WhatsThis`
  --> src/main.rs:14:13
   |
14 | /             fn uwu() -> Self {
15 | |                 <$this as Default>::default()
16 | |             }
   | |_____________^ not a member of trait `WhatsThis`
   |
  ::: src/ty6.rs:4:1
   |
4  | / uwuify
5  | | !
6  | | (Ty6);
   | |_____- in this macro invocation
   |
   = note: this error originates in the macro `uwuify` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0407]: method `uwu` is not a member of trait `WhatsThis`
  --> src/main.rs:14:13
   |
14 | /             fn uwu() -> Self {
15 | |                 <$this as Default>::default()
16 | |             }
   | |_____________^ not a member of trait `WhatsThis`
   |
  ::: src/ty7.rs:4:1
   |
4  | / uwuify
5  | | !
6  | | (Ty7);
   | |_____- in this macro invocation
   |
   = note: this error originates in the macro `uwuify` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0407]: method `uwu` is not a member of trait `WhatsThis`
  --> src/main.rs:14:13
   |
14 | /             fn uwu() -> Self {
15 | |                 <$this as Default>::default()
16 | |             }
   | |_____________^ not a member of trait `WhatsThis`
   |
  ::: src/ty8.rs:4:1
   |
4  | / uwuify
5  | | !
6  | | (Ty8);
   | |_____- in this macro invocation
   |
   = note: this error originates in the macro `uwuify` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0407]: method `uwu` is not a member of trait `WhatsThis`
  --> src/main.rs:14:13
   |
14 | /             fn uwu() -> Self {
15 | |                 <$this as Default>::default()
16 | |             }
   | |_____________^ not a member of trait `WhatsThis`
   |
  ::: src/ty9.rs:4:1
   |
4  | / uwuify
5  | | !
6  | | (Ty9);
   | |_____- in this macro invocation
   |
   = note: this error originates in the macro `uwuify` (in Nightly builds, run with -Z macro-backtrace for more info)

warning: `#[macro_use]` only has an effect on `extern crate` and modules
 --> src/main.rs:9:1
  |
9 | #[macro_use]
  | ^^^^^^^^^^^^
  |
  = note: `#[warn(unused_attributes)]` on by default

error[E0046]: not all trait items implemented, missing: `owo`
  --> src/main.rs:13:9
   |
13 |           impl WhatsThis for $this {
   |           ^^^^^^^^^^^^^^^^^^^^^^^^ missing `owo` in implementation
...
33 |       fn owo() -> Self;
   |       ----------------- `owo` from trait
   |
  ::: src/ty0.rs:4:1
   |
4  | / uwuify
5  | | !
6  | | (Ty0);
   | |_____- in this macro invocation
   |
   = note: this error originates in the macro `uwuify` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0046]: not all trait items implemented, missing: `owo`
  --> src/main.rs:13:9
   |
13 |           impl WhatsThis for $this {
   |           ^^^^^^^^^^^^^^^^^^^^^^^^ missing `owo` in implementation
...
33 |       fn owo() -> Self;
   |       ----------------- `owo` from trait
   |
  ::: src/ty1.rs:4:1
   |
4  | / uwuify
5  | | !
6  | | (Ty1);
   | |_____- in this macro invocation
   |
   = note: this error originates in the macro `uwuify` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0046]: not all trait items implemented, missing: `owo`
  --> src/main.rs:13:9
   |
13 |           impl WhatsThis for $this {
   |           ^^^^^^^^^^^^^^^^^^^^^^^^ missing `owo` in implementation
...
33 |       fn owo() -> Self;
   |       ----------------- `owo` from trait
   |
  ::: src/ty2.rs:4:1
   |
4  | / uwuify
5  | | !
6  | | (Ty2);
   | |_____- in this macro invocation
   |
   = note: this error originates in the macro `uwuify` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0046]: not all trait items implemented, missing: `owo`
  --> src/main.rs:13:9
   |
13 |           impl WhatsThis for $this {
   |           ^^^^^^^^^^^^^^^^^^^^^^^^ missing `owo` in implementation
...
33 |       fn owo() -> Self;
   |       ----------------- `owo` from trait
   |
  ::: src/ty3.rs:4:1
   |
4  | / uwuify
5  | | !
6  | | (Ty3);
   | |_____- in this macro invocation
   |
   = note: this error originates in the macro `uwuify` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0046]: not all trait items implemented, missing: `owo`
  --> src/main.rs:13:9
   |
13 |           impl WhatsThis for $this {
   |           ^^^^^^^^^^^^^^^^^^^^^^^^ missing `owo` in implementation
...
33 |       fn owo() -> Self;
   |       ----------------- `owo` from trait
   |
  ::: src/ty4.rs:4:1
   |
4  | / uwuify
5  | | !
6  | | (Ty4);
   | |_____- in this macro invocation
   |
   = note: this error originates in the macro `uwuify` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0046]: not all trait items implemented, missing: `owo`
  --> src/main.rs:13:9
   |
13 |           impl WhatsThis for $this {
   |           ^^^^^^^^^^^^^^^^^^^^^^^^ missing `owo` in implementation
...
33 |       fn owo() -> Self;
   |       ----------------- `owo` from trait
   |
  ::: src/ty5.rs:4:1
   |
4  | / uwuify
5  | | !
6  | | (Ty5);
   | |_____- in this macro invocation
   |
   = note: this error originates in the macro `uwuify` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0046]: not all trait items implemented, missing: `owo`
  --> src/main.rs:13:9
   |
13 |           impl WhatsThis for $this {
   |           ^^^^^^^^^^^^^^^^^^^^^^^^ missing `owo` in implementation
...
33 |       fn owo() -> Self;
   |       ----------------- `owo` from trait
   |
  ::: src/ty6.rs:4:1
   |
4  | / uwuify
5  | | !
6  | | (Ty6);
   | |_____- in this macro invocation
   |
   = note: this error originates in the macro `uwuify` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0046]: not all trait items implemented, missing: `owo`
  --> src/main.rs:13:9
   |
13 |           impl WhatsThis for $this {
   |           ^^^^^^^^^^^^^^^^^^^^^^^^ missing `owo` in implementation
...
33 |       fn owo() -> Self;
   |       ----------------- `owo` from trait
   |
  ::: src/ty7.rs:4:1
   |
4  | / uwuify
5  | | !
6  | | (Ty7);
   | |_____- in this macro invocation
   |
   = note: this error originates in the macro `uwuify` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0046]: not all trait items implemented, missing: `owo`
  --> src/main.rs:13:9
   |
13 |           impl WhatsThis for $this {
   |           ^^^^^^^^^^^^^^^^^^^^^^^^ missing `owo` in implementation
...
33 |       fn owo() -> Self;
   |       ----------------- `owo` from trait
   |
  ::: src/ty8.rs:4:1
   |
4  | / uwuify
5  | | !
6  | | (Ty8);
   | |_____- in this macro invocation
   |
   = note: this error originates in the macro `uwuify` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0046]: not all trait items implemented, missing: `owo`
  --> src/main.rs:13:9
   |
13 |           impl WhatsThis for $this {
   |           ^^^^^^^^^^^^^^^^^^^^^^^^ missing `owo` in implementation
...
33 |       fn owo() -> Self;
   |       ----------------- `owo` from trait
   |
  ::: src/ty9.rs:4:1
   |
4  | / uwuify
5  | | !
6  | | (Ty9);
   | |_____- in this macro invocation
   |
   = note: this error originates in the macro `uwuify` (in Nightly builds, run with -Z macro-backtrace for more info)

Some errors have detailed explanations: E0046, E0407.
For more information about an error, try `rustc --explain E0046`.
warning: `whats-this` (bin "whats-this") generated 1 warning
error: could not compile `whats-this` (bin "whats-this") due to 20 previous errors; 1 warning emitted
Desired output
error[E0407]: method `uwu` is not a member of trait `WhatsThis`
  --> src/main.rs:14:13
   |
14 | /             fn uwu() -> Self {
15 | |                 <$this as Default>::default()
16 | |             }
   | |_____________^ not a member of trait `WhatsThis`
   |
  ::: src/ty9.rs:4:1
   |
4  | / uwuify
5  | | !
6  | | (Ty9);
   | |_____- in this macro invocation and 9 others
   |
   = note: this error originates in the macro `uwuify` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0046]: not all trait items implemented, missing: `owo`
  --> src/main.rs:13:9
   |
13 |           impl WhatsThis for $this {
   |           ^^^^^^^^^^^^^^^^^^^^^^^^ missing `owo` in implementation
...
33 |       fn owo() -> Self;
   |       ----------------- `owo` from trait
   |
  ::: src/ty9.rs:4:1
   |
4  | / uwuify
5  | | !
6  | | (Ty9);
   | |_____- in this macro invocation and 9 others
   |
   = note: this error originates in the macro `uwuify` (in Nightly builds, run with -Z macro-backtrace for more info)

Some errors have detailed explanations: E0046, E0407.
For more information about an error, try `rustc --explain E0046`.
warning: `whats-this` (bin "whats-this") generated 1 warning
error: could not compile `whats-this` (bin "whats-this") due to 20 previous errors; 1 warning emitted
Rationale and extra context

The preferred output is to swallow these into a single error, since the rest is just terminal spam, basically. Even pointing at different files where this error occurs is not very helpful, as the actual issue is I need to rename something in the macro.

It seems rustc is just smart enough to swallow this if this is a repeating macro error in the same file (possibly the same macro invocation, haven't experimented beyond this), but that's not always the case, and "how (not) well-factored my code is" would ideally matter less to diagnostics.

As a bonus round: rustc could notice these two errors, recognize they're similar signatures except for names, and just ask me directly if I forgot to rename something, like:

error[E0407]: expanded `impl WhatsThis for $this` is missing a trait item: `owo`
  --> src/main.rs:14:13
   |
13 |           impl WhatsThis for $this {
   |           ^^^^^^^^^^^^^^^^^^^^^^^^ missing `owo` in implementation
...
33 |       fn owo() -> Self;
   |       ----------------- `owo` from trait
= note: `impl WhatsThis for $this` also has an item that is not a member of `trait WhatsThis`
14 | /             fn uwu() -> Self {
15 | |                 <$this as Default>::default()
16 | |             }
   | |_____________^ not a member of trait `WhatsThis`

= help: perhaps you meant to rename the item from `fn uwu` to `fn owo`?
Other cases

No response

Rust Version
rustc 1.80.0-nightly (ab14f944a 2024-05-13)
binary: rustc
commit-hash: ab14f944afe4234db378ced3801e637eae6c0f30
commit-date: 2024-05-13
host: x86_64-unknown-linux-gnu
release: 1.80.0-nightly
LLVM version: 18.1.4
Anything else?

@rustbot label: +A-macros

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with the linked uwu-er-i-mean-owo reproducer and run cargo check to inspect the repeated E0407 and E0046 diagnostics from the uwuify macro. Review the issue's example and determine how repeated errors should be recognized and represented. Done means the refactoring scenario produces a compressed, useful diagnostic without losing the relevant macro or source locations.

Written by the indexing model from the issue text.

Assessment

Tech stack
rust
Domain
compilers
Issue type
Feature
Difficulty
5/5
Estimated time
Over a week
Activity status
Stale
Clarity
Needs clarification
Newbie friendliness
25/100

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