portable-simd is entirely untested in rust-lang/rust

[RalfJung]

It looks like portable-simd doctests (and possibly the other tests as well) are entirely untested in this repo. Since #146882, some of the doctests are now failing to compile:

  0.000008   ---- crates/core_simd/src/simd/num/int.rs - core_simd::simd::num::int::SimdInt::abs_diff (line 81) stdout ----
  0.000007   error: use of deprecated constant `std::i32::MIN`: replaced by the `MIN` associated constant on this type
  0.000007     --> crates/core_simd/src/simd/num/int.rs:89:27
  0.000007      |
  0.000006   89 | let a = Simd::from_array([MIN, MAX, 100, -100]);
  0.000007      |                           ^^^
  0.000006      |
  0.000007   note: the lint level is defined here
  0.000007     --> crates/core_simd/src/simd/num/int.rs:79:9
  0.000007      |
  0.000007   79 | #![deny(warnings)]
  0.000006      |         ^^^^^^^^
  0.000007      = note: `#[deny(deprecated)]` implied by `#[deny(warnings)]`
  0.000007   
  0.000007   error: use of deprecated constant `std::i32::MAX`: replaced by the `MAX` associated constant on this type
  0.000008     --> crates/core_simd/src/simd/num/int.rs:89:32
  0.000005      |
  0.000005   89 | let a = Simd::from_array([MIN, MAX, 100, -100]);
  0.000004      |                                ^^^
  0.000005   
  0.000004   error: use of deprecated constant `std::i32::MAX`: replaced by the `MAX` associated constant on this type
  0.000005     --> crates/core_simd/src/simd/num/int.rs:90:27
  0.000004      |
  0.000005   90 | let b = Simd::from_array([MAX, MIN, -80, -120]);
  0.000004      |                           ^^^
  0.000005   
  0.000004   error: use of deprecated constant `std::i32::MIN`: replaced by the `MIN` associated constant on this type
  0.000005     --> crates/core_simd/src/simd/num/int.rs:90:32
  0.000004      |
  0.000005   90 | let b = Simd::from_array([MAX, MIN, -80, -120]);
  0.000004      |                                ^^^
  0.000005   
  0.000005   error: use of deprecated constant `std::i32::MIN`: replaced by the `MIN` associated constant on this type
  0.000004     --> crates/core_simd/src/simd/num/int.rs:88:17
  0.000005      |
  0.000008   88 | use core::i32::{MIN, MAX};
  0.000007      |                 ^^^
  0.000007   
  0.000007   error: use of deprecated constant `std::i32::MAX`: replaced by the `MAX` associated constant on this type
  0.000007     --> crates/core_simd/src/simd/num/int.rs:88:22
  0.000007      |
  0.000007   88 | use core::i32::{MIN, MAX};
  0.000007      |                      ^^^
  0.000010   
  0.000008   error: aborting due to 6 previous errors
  0.000012   
  0.000007   Couldn't compile the test.

We should have at least some basic "does it build" smoke tests running in this repo.

Cc @rust-lang/project-portable-simd

[RalfJung]

I am very surprised that apparently this is not run together with ./x test library/core --doc. These files are included as a regular module in libcore, aren't they?

[RalfJung]

@Kobzol any idea why these doctests apparently have not been run?

[RalfJung]

Hm, there's also something else that is odd... the output says int.rs:79 is where we configure deny(warnings) but there is no such thing there?

rust/library/portable-simd/crates/core_simd/src/simd/num/int.rs

Lines 77 to 91 in 7608eb7

	/// Lanewise absolute difference.
	/// Every element becomes the absolute difference of `self` and `second`.
	///
	/// # Examples
	/// ```
	/// # #![feature(portable_simd)]
	/// # #[cfg(feature = "as_crate")] use core_simd::simd;
	/// # #[cfg(not(feature = "as_crate"))] use core::simd;
	/// # use simd::prelude::*;
	/// use core::i32::{MIN, MAX};
	/// let a = Simd::from_array([MIN, MAX, 100, -100]);
	/// let b = Simd::from_array([MAX, MIN, -80, -120]);
	/// assert_eq!(a.abs_diff(b), Simd::from_array([u32::MAX, u32::MAX, 180, 20]));
	/// ```
	fn abs_diff(self, second: Self) -> Self::Unsigned;

Is rustdoc sometimes auto-inserting a deny(warnings)?

[RalfJung]

Ah, I think I found it... libcore has this

#![doc(
    html_playground_url = "https://play.rust-lang.org/",
    issue_tracker_base_url = "https://github.com/rust-lang/rust/issues/",
    test(no_crate_inject, attr(deny(warnings))),
    test(attr(allow(dead_code, deprecated, unused_variables, unused_mut, duplicate_features)))
)]

but portable-simd's core crate only has

#![doc(test(attr(deny(warnings))))]

Therefore the tests work fine when run as part of libcore, but don't work when run separately.