Targeted suggestions for specific "no method" errors on standard library types #59450
Labels
A-diagnostics
Area: Messages for errors, warnings, and lints
A-suggestion-diagnostics
Area: Suggestions generated by the compiler applied by `cargo fix`
C-enhancement
Category: An issue proposing an enhancement or a PR with one.
D-newcomer-roadblock
Diagnostics: Confusing error or lint; hard to understand for new users.
T-compiler
Relevant to the compiler team, which will review and decide on the PR/issue.
Comments
estebank
added
the
A-suggestion-diagnostics
|
Do you think this would be a common enough pattern that it'd be worth creating something like Something like |
|
Something similar to rustc_on_unimplemented sounds like it would work! I don't know enough about the diagnostics implementation to know what the other options are. Bonus points if it is straightforward for a new rustc contributor to add a confusable and corresponding test case. |
estebank
added
D-newcomer-roadblock
crlf0710
added
the
C-enhancement
|
We could also reuse (abuse?) |
|
Maybe relevant: #107108 adds |
bors
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Jul 16, 2023
…ons, r=cjgillot
Add `#[rustc_confusables]` attribute to allow targeted "no method" error suggestions on standard library types
After this PR, the standard library developer can annotate methods on e.g. `BTreeSet::push` with `#[rustc_confusables("insert")]`. When the user mistypes `btreeset.push()`, `BTreeSet::insert` will be suggested if there are no other candidates to suggest. This PR lays the foundations for contributors to add `rustc_confusables` annotations to standard library types for targeted suggestions, as specified in rust-lang#59450, or to address cases such as rust-lang#108437.
### Example
Assume `BTreeSet` is the standard library type:
```
// Standard library definition
#![feature(rustc_attrs)]
struct BTreeSet;
impl BTreeSet {
#[rustc_confusables("push")]
fn insert(&self) {}
}
// User code
fn main() {
let x = BTreeSet {};
x.push();
}
```
A new suggestion (which has lower precedence than suggestions for misspellings and only is shown when there are no misspellings suggestions) will be added to hint the user maybe they intended to write `x.insert()` instead:
```
error[E0599]: no method named `push` found for struct `BTreeSet` in the current scope
--> test.rs:12:7
|
3 | struct BTreeSet;
| --------------- method `push` not found for this struct
...
12 | x.push();
| ^^^^ method not found in `BTreeSet`
|
help: you might have meant to use `insert`
|
12 | x.insert();
| ~~~~~~
error: aborting due to previous error
```
|
Now that PR #112239 is merged, it should be easy to add |
estebank
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Feb 7, 2024
Help with common API confusion, like asking for `push` when the data structure really has `append`.
```
error[E0599]: no method named `size` found for struct `Vec<{integer}>` in the current scope
--> $DIR/rustc_confusables_std_cases.rs:17:7
|
LL | x.size();
| ^^^^
|
help: you might have meant to use `len`
|
LL | x.len();
| ~~~
help: there is a method with a similar name
|
LL | x.resize();
| ~~~~~~
```
rust-lang#59450
estebank
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Feb 10, 2024
Help with common API confusion, like asking for `push` when the data structure really has `append`.
```
error[E0599]: no method named `size` found for struct `Vec<{integer}>` in the current scope
--> $DIR/rustc_confusables_std_cases.rs:17:7
|
LL | x.size();
| ^^^^
|
help: you might have meant to use `len`
|
LL | x.len();
| ~~~
help: there is a method with a similar name
|
LL | x.resize();
| ~~~~~~
```
rust-lang#59450
estebank
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Feb 12, 2024
Help with common API confusion, like asking for `push` when the data structure really has `append`.
```
error[E0599]: no method named `size` found for struct `Vec<{integer}>` in the current scope
--> $DIR/rustc_confusables_std_cases.rs:17:7
|
LL | x.size();
| ^^^^
|
help: you might have meant to use `len`
|
LL | x.len();
| ~~~
help: there is a method with a similar name
|
LL | x.resize();
| ~~~~~~
```
rust-lang#59450
estebank
added a commit
to estebank/rust
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Feb 13, 2024
Help with common API confusion, like asking for `push` when the data structure really has `append`.
```
error[E0599]: no method named `size` found for struct `Vec<{integer}>` in the current scope
--> $DIR/rustc_confusables_std_cases.rs:17:7
|
LL | x.size();
| ^^^^
|
help: you might have meant to use `len`
|
LL | x.len();
| ~~~
help: there is a method with a similar name
|
LL | x.resize();
| ~~~~~~
```
rust-lang#59450
|
I'll have #120730 close this ticket. We can open new ones for specific methods that require more aliases. |
oli-obk
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Feb 15, 2024
Provide suggestions through `rustc_confusables` annotations
Help with common API confusion, like asking for `push` when the data structure really has `append`.
```
error[E0599]: no method named `size` found for struct `Vec<{integer}>` in the current scope
--> $DIR/rustc_confusables_std_cases.rs:17:7
|
LL | x.size();
| ^^^^
|
help: you might have meant to use `len`
|
LL | x.len();
| ~~~
help: there is a method with a similar name
|
LL | x.resize();
| ~~~~~~
```
Fix rust-lang#59450 (we can open subsequent tickets for specific cases).
Fix rust-lang#108437:
```
error[E0599]: `Option<{integer}>` is not an iterator
--> f101.rs:3:9
|
3 | opt.flat_map(|val| Some(val));
| ^^^^^^^^ `Option<{integer}>` is not an iterator
|
::: /home/gh-estebank/rust/library/core/src/option.rs:571:1
|
571 | pub enum Option<T> {
| ------------------ doesn't satisfy `Option<{integer}>: Iterator`
|
= note: the following trait bounds were not satisfied:
`Option<{integer}>: Iterator`
which is required by `&mut Option<{integer}>: Iterator`
help: you might have meant to use `and_then`
|
3 | opt.and_then(|val| Some(val));
| ~~~~~~~~
```
On type error of method call arguments, look at confusables for suggestion. Fix rust-lang#87212:
```
error[E0308]: mismatched types
--> f101.rs:8:18
|
8 | stuff.append(Thing);
| ------ ^^^^^ expected `&mut Vec<Thing>`, found `Thing`
| |
| arguments to this method are incorrect
|
= note: expected mutable reference `&mut Vec<Thing>`
found struct `Thing`
note: method defined here
--> /home/gh-estebank/rust/library/alloc/src/vec/mod.rs:2025:12
|
2025 | pub fn append(&mut self, other: &mut Self) {
| ^^^^^^
help: you might have meant to use `push`
|
8 | stuff.push(Thing);
| ~~~~
```
bors
added a commit
to rust-lang-ci/rust
that referenced
this issue
Feb 17, 2024
Provide suggestions through `rustc_confusables` annotations
Help with common API confusion, like asking for `push` when the data structure really has `append`.
```
error[E0599]: no method named `size` found for struct `Vec<{integer}>` in the current scope
--> $DIR/rustc_confusables_std_cases.rs:17:7
|
LL | x.size();
| ^^^^
|
help: you might have meant to use `len`
|
LL | x.len();
| ~~~
help: there is a method with a similar name
|
LL | x.resize();
| ~~~~~~
```
Fix rust-lang#59450 (we can open subsequent tickets for specific cases).
Fix rust-lang#108437:
```
error[E0599]: `Option<{integer}>` is not an iterator
--> f101.rs:3:9
|
3 | opt.flat_map(|val| Some(val));
| ^^^^^^^^ `Option<{integer}>` is not an iterator
|
::: /home/gh-estebank/rust/library/core/src/option.rs:571:1
|
571 | pub enum Option<T> {
| ------------------ doesn't satisfy `Option<{integer}>: Iterator`
|
= note: the following trait bounds were not satisfied:
`Option<{integer}>: Iterator`
which is required by `&mut Option<{integer}>: Iterator`
help: you might have meant to use `and_then`
|
3 | opt.and_then(|val| Some(val));
| ~~~~~~~~
```
On type error of method call arguments, look at confusables for suggestion. Fix rust-lang#87212:
```
error[E0308]: mismatched types
--> f101.rs:8:18
|
8 | stuff.append(Thing);
| ------ ^^^^^ expected `&mut Vec<Thing>`, found `Thing`
| |
| arguments to this method are incorrect
|
= note: expected mutable reference `&mut Vec<Thing>`
found struct `Thing`
note: method defined here
--> /home/gh-estebank/rust/library/alloc/src/vec/mod.rs:2025:12
|
2025 | pub fn append(&mut self, other: &mut Self) {
| ^^^^^^
help: you might have meant to use `push`
|
8 | stuff.push(Thing);
| ~~~~
```
estebank
added a commit
to estebank/rust
that referenced
this issue
Feb 22, 2024
Help with common API confusion, like asking for `push` when the data structure really has `append`.
```
error[E0599]: no method named `size` found for struct `Vec<{integer}>` in the current scope
--> $DIR/rustc_confusables_std_cases.rs:17:7
|
LL | x.size();
| ^^^^
|
help: you might have meant to use `len`
|
LL | x.len();
| ~~~
help: there is a method with a similar name
|
LL | x.resize();
| ~~~~~~
```
rust-lang#59450
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Rustc currently shows a perfectly reasonable error message when calling a nonexistent method:
But for specific frequently encountered cases, it would be great to show a more targeted error that gives the name of the method you almost definitely meant to call, despite not being similar enough to trigger the "did you mean" suggestion.
Candidates would be cases that arise often from refactoring (this applies to BTreeSet::push, which I see every now and then after replacing a Vec with a BTreeSet) or cases of a Rust API being named differently from an equivalent C++ API.
insertpushpush_backlenThe text was updated successfully, but these errors were encountered: