Suggest `!` for bitwise negation when encountering a `~` #41722

F001 · 2017-05-03T08:29:02Z

Here is a program

fn main() {
    let x = ~1;
}

It's output:

error: `~` can not be used as an unary operator
 --> /home/fcc/temp/test.rs:4:13
  |
4 |     let x = ~1;
  |             ^^
  |
  = help: use `!` instead of `~` if you meant to bitwise negation

cc @bstrie

rust-highfive · 2017-05-03T08:29:16Z

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @nikomatsakis (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 Due to the way GitHub handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed.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.

kennytm · 2017-05-03T08:42:03Z

You should add a test case (probably in src/test/ui/did_you_mean).

F001 · 2017-05-03T09:02:30Z

Thank you @kennytm . Test case added.

petrochenkov · 2017-05-03T12:10:57Z

src/libsyntax/parse/parser.rs

+                let (span, e) = self.interpolated_or_expr_span(e)?;
+                let mut err = self.diagnostic().struct_span_err(lo.to(span),
+                        "`~` can not be used as an unary operator");
+                err.help("use `!` instead of `~` if you meant to bitwise negation");


Could you also add err.span_label(span_of_tilda, "did you mean !?") and use span_of_tilda for the primary error as well?

meant to bitwise negation

Redundant "to"

meant to bitwise negation

Alternatively meant to perform bitwise negation.

Fixed. Thanks.

By span_of_tilda I actually meant the span of ~ itself (let span_of_tilda = self.span; self.bump();)

petrochenkov · 2017-05-03T12:14:25Z

src/libsyntax/parse/parser.rs

@@ -2700,6 +2700,17 @@ impl<'a> Parser<'a> {
                let (span, e) = self.interpolated_or_expr_span(e)?;
                (span, self.mk_unary(UnOp::Not, e))
            }
+            // fix issue #41679: Suggest `!` for bitwise negation when encountering a `~`


Nit: could you remove "fix issue #41679:"? (Not useful for a reader and the history is available from git if necessary.)

petrochenkov · 2017-05-03T12:17:32Z

src/libsyntax/parse/token.rs

@@ -201,6 +201,7 @@ impl Token {
            OpenDelim(..)               => true, // tuple, array or block
            Literal(..)                 => true, // literal
            Not                         => true, // operator not
+            Tilde                       => true, // operator not (incorrect)


This is slightly risky, can_begin_expr can affect syntax accepted by parser in general, not only diagnostics.
~ is not used anywhere right now, so it's ok for now, but it may be used in the future.

Yeah, I agree. I have deleted this line, and the test works fine. At least for this case, it is not necessary to modify can_begin_expr .

This will remove the suggestion from something like return ~0, but that's more or less ok.

nagisa · 2017-05-03T13:26:33Z

I had hoped we could avoid adding a token here.

@petrochenkov I did use ~ a number of times as a separator in macros by example. You sure there’s no way it will affect them?

estebank · 2017-05-03T17:32:43Z

I had hoped we could avoid adding a token here.

@nagisa Tilde is already a token, it wasn't added in this PR.

F001 · 2017-05-04T09:45:59Z

@aidanhs Comments are resolved. Do you have other concerns?

petrochenkov · 2017-05-04T12:52:24Z

@nagisa
I could imagine this breaking something like

macro_rules! m {
    ($x: expr) => {};
    (~ $x: expr) => {};
}

fn main() {
    m!(~x); // ERROR expected expression, found `~`
}

but it doesn't seem to work already.

petrochenkov · 2017-05-04T12:57:05Z

r=me modulo #41722 (comment)

F001 · 2017-05-05T01:43:11Z

r? @petrochenkov
Thanks very much for your patient guidance!

petrochenkov · 2017-05-05T09:06:41Z

@bors r+

bors · 2017-05-05T09:06:42Z

📌 Commit a9d3b34 has been approved by petrochenkov

arqunis · 2017-05-05T20:12:47Z

src/libsyntax/parse/parser.rs

+                let (span, e) = self.interpolated_or_expr_span(e)?;
+                let span_of_tilde = lo;
+                let mut err = self.diagnostic().struct_span_err(span_of_tilde,
+                        "`~` can not be used as an unary operator");


Bit of a late review, but won't hurt. Anyway, this should be using "a" because unary doesn't start with a vowel sound (As in, it starts with "you").

@acdenisSK Looks like this PR has already been merged, would you like to submit a minor PR to fix this?

Ah, i guess, gimme a sec.

@bstrie

Suggest `!` for bitwise negation when encountering a `~` Fix rust-lang#41679 Here is a program ```rust fn main() { let x = ~1; } ``` It's output: ``` error: `~` can not be used as an unary operator --> /home/fcc/temp/test.rs:4:13 | 4 | let x = ~1; | ^^ | = help: use `!` instead of `~` if you meant to bitwise negation ``` cc @bstrie

Rollup of 9 pull requests - Successful merges: #41064, #41307, #41512, #41582, #41678, #41722, #41734, #41761, #41763 - Failed merges:

bors · 2017-05-06T01:46:50Z

⌛ Testing commit a9d3b34 with merge 42a4f37...

lambda-fairy · 2017-05-10T09:08:39Z

@petrochenkov I believe that's covered by #27832

rust-highfive assigned nikomatsakis May 3, 2017

petrochenkov reviewed May 3, 2017

View reviewed changes

aidanhs added the S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. label May 3, 2017

rust-highfive assigned petrochenkov and unassigned nikomatsakis May 5, 2017

Suggest ! for bitwise negation when encountering a ~

a9d3b34

arqunis suggested changes May 5, 2017

View reviewed changes

frewsxcv mentioned this pull request May 5, 2017

Rollup of 9 pull requests #41773

Merged

bors added a commit that referenced this pull request May 5, 2017

Auto merge of #41773 - frewsxcv:rollup, r=frewsxcv

42a4f37

Rollup of 9 pull requests - Successful merges: #41064, #41307, #41512, #41582, #41678, #41722, #41734, #41761, #41763 - Failed merges:

bors merged commit a9d3b34 into rust-lang:master May 6, 2017

F001 deleted the warnTilde branch May 7, 2017 02:13

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Suggest `!` for bitwise negation when encountering a `~` #41722

Suggest `!` for bitwise negation when encountering a `~` #41722

F001 commented May 3, 2017

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lambda-fairy commented May 10, 2017

Suggest ! for bitwise negation when encountering a ~ #41722

Suggest ! for bitwise negation when encountering a ~ #41722

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F001 commented May 3, 2017

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lambda-fairy commented May 10, 2017

Suggest `!` for bitwise negation when encountering a `~` #41722

Suggest `!` for bitwise negation when encountering a `~` #41722