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Invalid char literal error message has an unhelpful snippet #30033

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apasel422 opened this issue Nov 24, 2015 · 4 comments
Closed

Invalid char literal error message has an unhelpful snippet #30033

apasel422 opened this issue Nov 24, 2015 · 4 comments
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A-diagnostics Area: Messages for errors, warnings, and lints A-parser Area: The parsing of Rust source code to an AST

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@apasel422
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foo.rs:

fn main() {
    let _ = 'ab';
}
foo.rs:2:16: 2:18 error: character literal may only contain one codepoint: ';
foo.rs:2     let _ = 'ab';
                        ^~

The snippet at the end of the error message is not helpful, and should probably encompass everything between the two 's.
@apasel422 apasel422 added A-diagnostics Area: Messages for errors, warnings, and lints A-parser Area: The parsing of Rust source code to an AST labels Nov 24, 2015
@gchp
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gchp commented Jan 6, 2016

I get a different error for your example.

test.rs:2:16: 2:18 error: unterminated character constant: ';
test.rs:2     let _ = 'ab';
                         ^~

$ rustc -V
rustc 1.5.0 (3d7cd77e4 2015-12-04)

@apasel422
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The error message from the original issue remains the same on nightly.

@gchp
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gchp commented Jan 6, 2016

Ah, sorry, I didn't test with nightly. I see the error now.

@gchp
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gchp commented Jan 6, 2016

Gonna take a crack at this issue. Should have a PR up soon, seems simple enough.

@gchp gchp mentioned this issue Jan 7, 2016
Merged
gchp added a commit to gchp/rust that referenced this issue Jan 14, 2016
@gchp
Display better snippet for invalid char literal
acc9428 
Given this code:

    fn main() {
        let _ = 'abcd';
    }

The compiler would give a message like:

    error: character literal may only contain one codepoint: ';
    let _ = 'abcd';
                 ^~

With this change, the message now displays:

    error: character literal may only contain one codepoint: 'abcd'
    let _ = 'abcd'
            ^~~~~~

Fixes rust-lang#30033
bors added a commit that referenced this issue Jan 15, 2016
@bors
Auto merge of #30763 - gchp:issue/30033, r=nagisa
a70a60a 
This is achieved by adding the scan_back method. This method looks back
through the source_text of the StringReader until it finds the target
char, returning it's offset in the source. We use this method to find
the offset of the opening single quote, and use that offset as the start
of the error.

Given this code:

```rust
fn main() {
    let _ = 'abcd';
}
```

The compiler would give a message like:

```
error: character literal may only contain one codepoint: ';
let _ = 'abcd';
             ^~
```
With this change, the message now displays:

```
error: character literal may only contain one codepoint: 'abcd';
let _ = 'abcd';
        ^~~~~~~
```

Fixes #30033
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