`cargo test --doc -- --ignored` appears to build and run examples anotated with ```ignore but doesn't, or at least it does not report any failures.

Problem

Given a documentation example that does not build (or builds but fails execution), annotated with ```ignore, I expect:

1. Running cargo test --doc reports the example as ignored. No failures are reported. => Correct.
2. Running cargo test --doc -- --ignored builds (and runs) the sample and reports the build (or execution) errors => Incorrect.
   a. The example is reported as built and run.
   b. The example is reported as succesful.
3. (Surprisingly?), running cargo test --doc -- --ignored --show-output has the expected behaviour. => Correct
   a . The example is reported as built (or built and run).
   b. Build (or execution) failures are reported.

Steps

Given the following src\lib.rs

/// # Example
/// ```ignore
/// let x = UnknownType::new();
/// println!("Doesn't build");
/// ```
pub fn no_build(left: u64, right: u64) -> u64 {
    left + right
}

/// # Example
/// ```ignore
/// assert!(false);
/// println!("Builds but fails");
/// ```
pub fn build_no_run(left: u64, right: u64) -> u64 {
    left * right
}

/// # Example
/// ```ignore
/// println!("Builds and succeeds");
/// ```
pub fn succeeds(left: u64, right: u64) -> u64 {
    left - right
}

and Cargo.toml

[package]
name = "bar"
version = "0.1.0"
edition = "2024"

[dependencies]

1. Run cargo test --doc -- --ignored
2. See (unexpected) output

        Doc-tests bar
   
   running 3 tests
   test src\lib.rs - build_no_run (line 11) ... ok
   test src\lib.rs - no_build (line 2) ... ok
   test src\lib.rs - succeeds (line 20) ... ok
   
   test result: ok. 3 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s
   

3. Run cargo test --doc -- --ignored --show-output
4. See (expected) output

       Doc-tests bar
   
   running 3 tests
   test src\lib.rs - no_build (line 2) ... FAILED
   test src\lib.rs - succeeds (line 20) ... ok
   test src\lib.rs - build_no_run (line 11) ... FAILED
   
   successes:
   
   successes:
       src\lib.rs - succeeds (line 20)
   
   failures:
   
   ---- src\lib.rs - no_build (line 2) stdout ----
   error[E0433]: failed to resolve: use of undeclared type `UnknownType`
    --> src\lib.rs:3:9
     |
   3 | let x = UnknownType::new();
     |         ^^^^^^^^^^^ use of undeclared type `UnknownType`
   
   error: aborting due to 1 previous error
   
   For more information about this error, try `rustc --explain E0433`.
   Couldn't compile the test.
   ---- src\lib.rs - build_no_run (line 11) stdout ----
   Test executable failed (exit code: 101).
   
   stderr:
   
   thread 'main' panicked at src\lib.rs:3:1:
   assertion failed: false
   note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
   
   failures:
       src\lib.rs - build_no_run (line 11)
       src\lib.rs - no_build (line 2)
   
   test result: FAILED. 1 passed; 2 failed; 0 ignored; 0 measured; 0 filtered out; finished in 6.12s
   
   error: doctest failed, to rerun pass `--doc`
   
   

Possible Solution(s)

No response

Notes

No response

Version

cargo 1.88.0 (873a06493 2025-05-10)
release: 1.88.0
commit-hash: 873a0649350c486caf67be772828a4f36bb4734c
commit-date: 2025-05-10
host: x86_64-pc-windows-msvc
libgit2: 1.9.0 (sys:0.20.0 vendored)
libcurl: 8.12.1-DEV (sys:0.4.80+curl-8.12.1 vendored ssl:Schannel)
os: Windows 10.0.22631 (Windows 11 Enterprise) [64-bit]

Reproduce the issue with the documented src/lib.rs and Cargo.toml using cargo test --doc -- --ignored and compare it with --show-output. Inspect the doctest handling behind these command entry points; done means ignored examples are built and executed when requested, with compilation or execution failures reported consistently without requiring --show-output.