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Add help message for incorrect pattern syntax #47232

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merged 7 commits into from
Jan 8, 2018
Merged

Add help message for incorrect pattern syntax #47232

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41f58a7
Add help message for incorrect pattern syntax
keatinge Jan 6, 2018
13576df
fix capitalization
keatinge Jan 6, 2018
dcb53d7
Emit non-fatal error instead
keatinge Jan 6, 2018
4436bca
fix style
keatinge Jan 6, 2018
8260209
Add tests for error message for pattern matching typo
keatinge Jan 6, 2018
a9b746b
Use span_suggestion instead of span_err_help
keatinge Jan 6, 2018
6aafdc3
Fix tidy error
keatinge Jan 6, 2018
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13 changes: 11 additions & 2 deletions src/libsyntax/parse/parser.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -3431,8 +3431,17 @@ impl<'a> Parser<'a> {
let mut pats = Vec::new();
loop {
pats.push(self.parse_pat()?);
if self.check(&token::BinOp(token::Or)) { self.bump();}
else { return Ok(pats); }

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());
err.emit();

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@keatinge keatinge Jan 6, 2018 •
edited
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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 '|': '|'

self.bump();
} else if self.check(&token::BinOp(token::Or)) {
self.bump();
} else {
return Ok(pats);
}
};
}

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17 changes: 17 additions & 0 deletions src/test/ui/did_you_mean/multiple-pattern-typo.rs
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@@ -0,0 +1,17 @@
// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

fn main() {
let x = 3;
match x {
1 | 2 || 3 => (), //~ ERROR unexpected token `||` after pattern
_ => (),
}
}
10 changes: 10 additions & 0 deletions src/test/ui/did_you_mean/multiple-pattern-typo.stderr
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@@ -0,0 +1,10 @@
error: unexpected token `||` after pattern
--> $DIR/multiple-pattern-typo.rs:14:15
|
14 | 1 | 2 || 3 => (), //~ ERROR unexpected token `||` after pattern
| ^^
|
= help: did you mean to use `|` to specify multiple patterns?

error: aborting due to previous error