Running rustdoc using https://github.com/eddyb/rust/tree/250dc4e5691d68ecb051a1fd11a21cbee8c68fb7

lib.rs

#![crate_name = "parser"]
#![crate_type = "lib"]

use std::ops::Add;

/// ```
/// use parser::test;
/// 
/// assert_eq!(test::<i32>(1)(2), 3);
/// ```
pub fn test<'a, I: 'a + Add<I, Output=I>>(i: I) -> impl FnOnce(I) -> I + 'a {
    |a| a + i
}

terminal.txt

➜  src  rustc lib.rs
➜  src  rustdoc --test -L. lib.rs

running 1 test
test test_0 ... FAILED

failures:

---- test_0 stdout ----
        thread 'test_0' panicked at 'lookup_item: id not found: 9', src/librustc/metadata/decoder.rs:99



failures:
    test_0

test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured

thread '<unnamed>' panicked at 'Some tests failed', src/libtest/lib.rs:253