Add help message for incorrect pattern syntax#47232
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| else { | ||
| // Accidental use of || instead of | inbetween patterns | ||
| if self.token == token::OrOr { | ||
| return Err(self.span_fatal_help( |
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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.
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So I just need to emit the error instead?
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Yes, emit an error (non-fatal one) and continue parsing.
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Can you take a look now?
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This also needs a test (#46763 has an example of this as well). |
| if self.token == token::OrOr { | ||
| self.span_err_help(self.span, | ||
| "unexpected token `||` after pattern", | ||
| "did you mean to use `|` to specify multiple patterns?"); |
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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());
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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 '|': '|'
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@bors r+ |
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📌 Commit 6aafdc3 has been approved by |
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: