Add help message for incorrect pattern syntax #47232
Conversation
|
Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @arielb1 (or someone else) soon. If any changes to this PR are deemed necessary, please add them as extra commits. This ensures that the reviewer can see what has changed since they last reviewed the code. Due to the way GitHub handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed. Large or tricky changes may require several passes of review and changes. Please see the contribution instructions for more information. |
src/libsyntax/parse/parser.rs
Outdated
| else { | ||
| // Accidental use of || instead of | inbetween patterns | ||
| if self.token == token::OrOr { | ||
| return Err(self.span_fatal_help( |
There was a problem hiding this comment.
This is an instance of "confusable tokens" pattern, so we can easily do recovery instead of returning Err.
See #46763 for the example of how to do it, except that we have | and || instead of .. and ... here.
There was a problem hiding this comment.
So I just need to emit the error instead?
There was a problem hiding this comment.
Yes, emit an error (non-fatal one) and continue parsing.
There was a problem hiding this comment.
Can you take a look now?
|
This also needs a test (#46763 has an example of this as well). |
src/libsyntax/parse/parser.rs
Outdated
| if self.token == token::OrOr { | ||
| self.span_err_help(self.span, | ||
| "unexpected token `||` after pattern", | ||
| "did you mean to use `|` to specify multiple patterns?"); |
There was a problem hiding this comment.
When we have the relevant spans and know what code to suggest, the .span_suggestion method is arguably preferable (compact, attractive output; usable by tooling cc #42823).
let mut err = self.struct_span_err(self.span, "unexpected token `||` after pattern");
err.span_suggestion(self.span, "to specify multiple patterns, use `|`", "|".to_owned());
err.emit();There was a problem hiding this comment.
I hope it's okay that I switched up the sentence a little bit because the exact text you have looks confusing when it's actually printed to specify multiple patterns use '|': '|'
|
@bors r+ |
|
📌 Commit 6aafdc3 has been approved by |
petrochenkov
added
the
S-waiting-on-bors
Add help message for incorrect pattern syntax
When I was getting started with rust I often made the mistake of using `||` instead of `|` to match multiple patterns and spent a long time staring at my code wondering what was wrong.
for example:
```
fn main() {
let x = 1;
match x {
1 || 2 => println!("1 or 2"),
_ => println!("Something else"),
}
}
```
If you compile this with current rustc you will see
```
error: expected one of `...`, `..=`, `..`, `=>`, `if`, or `|`, found `||`
--> test.rs:5:11
|
5 | 1 || 2 => println!("1 or 2"),
| -^^ unexpected token
| |
| expected one of `...`, `..=`, `..`, `=>`, `if`, or `|` here
error: aborting due to previous error
```
With my proposed change it will show:
```
error: unexpected token `||` after pattern
--> test.rs:5:11
|
5 | 1 || 2 => println!("1 or 2"),
| ^^
|
= help: did you mean to use `|` to specify multiple patterns instead?
error: aborting due to previous error
```
|
☀️ Test successful - status-appveyor, status-travis |
When I was getting started with rust I often made the mistake of using
||instead of|to match multiple patterns and spent a long time staring at my code wondering what was wrong.for example:
If you compile this with current rustc you will see
With my proposed change it will show: