Better Debug impl for io::Error.

[clarfonthey]

This PR includes the below changes:

1. The former impl wrapped the entire thing in Error { repr: ... } which was unhelpful; this has been removed.
2. The Os variant of io::Error included the code and message, but not the kind; this has been fixed.
3. The Custom variant of io::Error included a Custom(Custom { ... }), which is now just Custom { ... }.

Example of previous impl:

Error {
    repr: Custom(
        Custom {
            kind: InvalidData,
            error: Error {
                repr: Os {
                    code: 2,
                    message: "no such file or directory"
                }
            }
        }
    )
}

Example of new impl:

Custom {
    kind: InvalidData,
    error: Os {
        code: 2,
        kind: NotFound,
        message: "no such file or directory"
    }
}

[rust-highfive]

r? @dtolnay

(rust_highfive has picked a reviewer for you, use r? to override)

[dtolnay]

Thanks!

[dtolnay]

@bors r+

[bors]

📌 Commit f058dce has been approved by dtolnay

[clarfonthey]

I forgot a stability attribute so you'll have to r+ again.

[dtolnay]

@bors r+

[bors]

📌 Commit 418d050 has been approved by dtolnay

[frewsxcv]

@bors rollup

[frewsxcv]

[01:09:58] failures:
[01:09:58]     io::error::test::test_debug_error
[01:09:58] 
[01:09:58] test result: FAILED. 788 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out

@bors r-

[ollie27]

As Debug has been implemented for io::Error since 1.0.0 #[stable(feature = "rust1", since = "1.0.0")] would make more sense here.

[clarfonthey]

Will do

[clarfonthey]

I fixed the test, changed the stability attribute, and also added a kind field to the OS error debug considering how that wasn't included but could be useful.

[dtolnay]

Could you update your comment at the top of this thread with an accurate before and after? The after Os representation should include the new kind field and the Custom looks like it should be getting formatted as a tuple struct according to the code.

[clarfonthey]

@dtolnay done! I also modified the failing test with one that's closer to the one listed in the OP.

[kennytm]

Should be {{ here.

[01:18:41] error: invalid format string: expected `'}'`, found `'k'`
[01:18:41]    --> /checkout/src/libstd/io/error.rs:590:13
[01:18:41]     |
[01:18:41] 590 | /             "Custom { \
[01:18:41] 591 | |                 kind: InvalidInput, \
[01:18:41] 592 | |                 error: Os {{ \
[01:18:41] 593 | |                     code: {:?}, \
[01:18:41] ...   |
[01:18:41] 596 | |                 }} \
[01:18:41] 597 | |             }}",
[01:18:41]     | |_______________^

[clarfonthey]

I'm fairly certain that I've fixed the build errors. Waiting on CI.

[dtolnay]

Travis says:

error[E0308]: mismatched types
   --> /checkout/src/libstd/io/error.rs:582:32
    |
582 |               repr: Repr::Custom(Custom {
    |  ________________________________^
583 | |                 kind: ErrorKind::InvalidInput,
584 | |                 error: box Error {
585 | |                     repr: super::Repr::Os(code)
586 | |                 },
587 | |             })
    | |_____________^ expected struct `realstd::boxed::Box`, found struct `io::error::Custom`
    |
    = note: expected type `realstd::boxed::Box<io::error::Custom>`
               found type `io::error::Custom`

[shepmaster]

Ping from triage, @clarcharr! Will you have time to address the build issues?

[killercup]

Build issue seems to be addressed, CI is green, so I'm gonna go ahead and

@bors r=dtolnay

[bors]

📌 Commit 52e074e has been approved by dtolnay