Update a bunch of library types for MCP807 #135236

scottmcm · 2025-01-08T08:09:04Z

This greatly reduces the number of places that actually use the rustc_layout_scalar_valid_range_* attributes down to just 3:

library/core\src\ptr\non_null.rs
68:#[rustc_layout_scalar_valid_range_start(1)]

library/core\src\num\niche_types.rs
19:        #[rustc_layout_scalar_valid_range_start($low)]
20:        #[rustc_layout_scalar_valid_range_end($high)]

Everything else -- PAL Nanoseconds, alloc's Cap, niched FDs, etc -- all just wrap those niche_types types.

r? ghost

juntyr · 2025-01-09T06:20:53Z

library/core/src/num/nonzero.rs

-                #[derive(Clone, Copy)]
-                #[repr(transparent)]
-                #[rustc_layout_scalar_valid_range_start(1)]
-                #[rustc_nonnull_optimization_guaranteed]


I didn't see this attribute in the new code for the non zero integers

Good catch! Thank you.

Oh, actually, I think it's fine. The inner ones don't need it because they're not exactly the guaranteed ones, rather the NonZero wrapper struct has it:

rust/library/core/src/num/nonzero.rs

Lines 122 to 126 in 62bf38f

#[stable(feature = "generic_nonzero", since = "1.79.0")]

#[repr(transparent)]

#[rustc_nonnull_optimization_guaranteed]

#[rustc_diagnostic_item = "NonZero"]

pub struct NonZero<T: ZeroablePrimitive>(T::NonZeroInner);

This greatly reduces the number of places that actually use the `rustc_layout_scalar_valid_range_*` attributes down to just 3: ``` library/core\src\ptr\non_null.rs 68:#[rustc_layout_scalar_valid_range_start(1)] library/core\src\num\niche_types.rs 19: #[rustc_layout_scalar_valid_range_start($low)] 20: #[rustc_layout_scalar_valid_range_end($high)] ``` Everything else -- PAL Nanoseconds, alloc's `Cap`, niched FDs, etc -- all just wrap those `niche_types` types.

scottmcm · 2025-01-10T19:36:47Z

Yay, finally got through CI 🎉

Hmm, since PAL changes, how about
r? @ChrisDenton

@rustbot ready

library/alloc/src/raw_vec.rs

ChrisDenton

This looks great! And thanks to juntyr for reviewing too.

ChrisDenton · 2025-01-10T22:43:48Z

library/core/src/num/mod.rs

+/// 100% perma-unstable
+#[doc(hidden)]
+pub mod niche_types;


It's a shame there isn't a way to say "this is pub only for alloc/std". But I guess having it be unstable is good enough.

Yeah, there's a bunch of issue = "none" stuff so that alloc and core can both use it :/

ChrisDenton · 2025-01-10T22:43:51Z

library/core/src/num/niche_types.rs

+        impl $name {
+            #[inline]
+            pub const unsafe fn new_unchecked(val: $int) -> Self {
+                // SAFETY: same precondition


It's kinda weird to write "same precondition" here as it isn't entirely clear what "same" is referring to. In any case, I think a bit of repetition here would be fine. Especially if things get moved around in the future.

Agreed, especially now that it's used cross-crates. (An earlier version of this it was pub(super) and I didn't care as much.) Put proper /// docs and SAFETY on it.

ChrisDenton · 2025-01-11T05:13:25Z

Thanks!

@bors r+

bors · 2025-01-11T05:13:28Z

📌 Commit ebd6d3f has been approved by ChrisDenton

It is now in the queue for this repository.

scottmcm mentioned this pull request Jan 8, 2025

Tracking issue for banning field projecting into [rustc_layout_scalar_valid_range_*] types (MCP807) #133652

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