Rustdoc example errors shifts one line

blonk · September 22, 2024, 11:48am

This has been an issue for basically as long as I can remember, and I'm curious if it's a known issue or just a local phenomenon:

When I run cargo test and there's a compile error in a doc test, the compiler will often, but not always, report the error one line off. Just now, the console output says an error is on line 64, but it's actually on line 63.

As far has I can remember, this has been the case for years.

It's a minor annoyance since when I go to the line, the actual error is just one line off, but still -- it's a little strange. Feels like a off-by-one error. I haven't been able to isolate when it starts happening, but once it does, it seems to be 100% reproducible and consistent.

jofas · September 22, 2024, 11:58am

The rustdoc team is aware of this:

github.com/rust-lang/rust

Line numbers in diagnostics for doctests are off by number of preceding hidden lines that aren't `use core;`

opened 12:08PM - 23 Mar 24 UTC

zopsicle

T-rustdoc A-diagnostics

### Code ```Rust /// ``` /// # use playground::f; /// x /// ``` pub fn f…() { todo!() } ``` Note that the expression `x` occurs on line 3 in the source code. ### Current output ```Shell error[E0425]: cannot find value `x` in this scope --> src/lib.rs:4:1 | 6 | x | ^ help: a function with a similar name exists: `f` | ::: /playground/src/lib.rs:5:1 | 5 | pub fn f() | ---------- similarly named function `f` defined here ``` Note that the diagnostic refers to line 4. ### Desired output ```Shell error[E0425]: cannot find value `x` in this scope --> src/lib.rs:3:1 | 6 | x | ^ help: a function with a similar name exists: `f` | ::: /playground/src/lib.rs:5:1 | 5 | pub fn f() | ---------- similarly named function `f` defined here ``` ### Rationale and extra context _No response_ ### Other cases _No response_ ### Rust Version ```Shell $ rustc --version --verbose rustc 1.77.0 (aedd173a2 2024-03-17) binary: rustc commit-hash: aedd173a2c086e558c2b66d3743b344f977621a7 commit-date: 2024-03-17 host: x86_64-unknown-linux-gnu release: 1.77.0 LLVM version: 17.0.6 ``` ### Anything else? This doesn't always seem to happen, for example in the following example it does not: ```rust /// ``` /// # use core; /// x /// ``` pub fn f() { } ``` ```Shell error[E0425]: cannot find value `x` in this scope --> src/lib.rs:3:1 | 4 | x | ^ not found in this scope ``` I'm not sure what makes the difference. The only difference in the code is that one imports `playground::f` and the other imports `core`.

system · December 21, 2024, 11:58am

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Rustdoc example errors shifts one line

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