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"did you mean" for misusing a field as a method is misleading #38321

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whitequark opened this issue Dec 12, 2016 · 11 comments
Closed

"did you mean" for misusing a field as a method is misleading #38321

whitequark opened this issue Dec 12, 2016 · 11 comments
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A-diagnostics Area: Messages for errors, warnings, and lints T-compiler Relevant to the compiler team, which will review and decide on the PR/issue.

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@whitequark
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whitequark commented Dec 12, 2016 •
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The error is currently:

error: no method named `src_addr` found for type `&wire::ipv4::Repr` in the current scope
   --> src/wire/ipv4.rs:409:34
    |
409 |         packet.set_src_addr(self.src_addr());
    |                                  ^^^^^^^^
    |
note: did you mean to write `self.src_addr`?
   --> src/wire/ipv4.rs:409:34
    |
409 |         packet.set_src_addr(self.src_addr());
    |                                  ^^^^^^^^

which is of course absurd.

To reproduce:

struct Foo {
    src_addr: usize
}

fn main() {
    let foo = Foo { src_addr: 10 };
    foo.src_addr()
}
@KalitaAlexey
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Why is it misleading?

@frewsxcv
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frewsxcv commented Dec 12, 2016 •
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@whitequark Are you able to share the project where you encountered this error?

@whitequark
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Why is it misleading?

Because it suggests to write the same thing as is already written.

@frewsxcv
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Why is it misleading?

Because it suggests to write the same thing as is already written.

The suggestion is telling you to write self.src_addr instead of self.src_addr(), since there is presumably a field (not a method) on your structure called src_addr.

@whitequark
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whitequark commented Dec 12, 2016 •
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The suggestion is telling you to write self.src_addr instead of self.src_addr(), since there is presumably a field (not a method) on your structure called src_addr.

It points to src_addr (not src_addr()) and suggests to write src_addr. This makes no sense. It should at least highlight the parens so that it points to src_addr().

@whitequark
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I've added a minimal repro to the issue text.

@frewsxcv frewsxcv added the A-diagnostics Area: Messages for errors, warnings, and lints label Dec 12, 2016
@whitequark
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Also, ideally it would highlight the entire self.src_addr() expression, not just the single token, since that's what it talks about in the error anyhow.

@KalitaAlexey
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I've got. It's a span problem.

@TheZoq2
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TheZoq2 commented Jan 3, 2017

I just ran into this aswell. I agree that it would be more clear if it highlighted the whole src_addr() instead of just src_addr but adding a note saying something along the lines of

There is no method called src_addr, did you mean to access the field src_addr?

Would be even more helpfull

@zackmdavis
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Yes, I found this confusing, too. I should submit a PR to fix this tomorrow (have code fix, but still need to correct compile-fail test expectations, but even more than that, need to sleep).

@zackmdavis
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okay, not literally tomorrow, but soon

zackmdavis added a commit to zackmdavis/rust that referenced this issue Feb 1, 2017
@zackmdavis
use help rather than span note for no method error; a slight rephrasing
17bfd14 
The use of the `span_note` diagnostic method resulted in error messages
that some users (including the present author) found very confusing: the
code snippet and highlighted span displayed with the "did you mean" note
was easy to interpret as a suggested edit (as if it had been set by
`span_suggestion`), but was in fact identical to the snippet/span
displayed just above, indicating the error in the original code, making
it look as if the compiler was suggesting a no-op change.

To remedy this, we use `help` instead of `span_note`, and reword one of
the affected messages to emphasize the concept of accessing a field
being different from calling a method (when the message just said, "did
you mean to write `self.foo`", it was not immediately obvious that this
was meant in contrast to `self.foo()`, with method-call parens).

Resolves rust-lang#38321.
@zackmdavis zackmdavis mentioned this issue Feb 1, 2017
Closed
@steveklabnik steveklabnik added the T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. label Mar 9, 2017
@estebank estebank mentioned this issue Mar 25, 2017
Merged
frewsxcv added a commit to frewsxcv/rust that referenced this issue Mar 29, 2017
@frewsxcv
Rollup merge of rust-lang#40816 - estebank:issue-38321, r=nikomatsakis
7f1083e 
Clarify suggetion for field used as method

Instead of

```rust
error: no method named `src_addr` found for type `&wire::ipv4::Repr` in the current scope
   --> src/wire/ipv4.rs:409:34
    |
409 |         packet.set_src_addr(self.src_addr());
    |                                  ^^^^^^^^
    |
note: did you mean to write `self.src_addr`?
   --> src/wire/ipv4.rs:409:34
    |
409 |         packet.set_src_addr(self.src_addr());
    |                                  ^^^^^^^^
```

present

```rust
error: no method named `src_addr` found for type `&wire::ipv4::Repr` in the current scope
   --> src/wire/ipv4.rs:409:34
    |
409 |         packet.set_src_addr(self.src_addr());
    |                                  ^^^^^^^^ field, not a method
    |
    = help: did you mean to write `self.src_addr` instead of `self.src_addr(...)`?
```

Fix rust-lang#38321.
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@steveklabnik @whitequark @frewsxcv @zackmdavis @TheZoq2 @KalitaAlexey