Rollup merge of rust-lang#87170 - xFrednet:clippy-5393-add-diagnostic-items, r=Manishearth,oli-obk

Add diagnostic items for Clippy

This adds a bunch of diagnostic items to `std`/`core`/`alloc` functions, structs and traits used in Clippy. The actual refactorings in Clippy to use these items will be done in a different PR in Clippy after the next sync.

This PR doesn't include all paths Clippy uses, I've only gone through the first 85 lines of Clippy's [`paths.rs`](https://github.com/rust-lang/rust-clippy/blob/ecf85f4bdc319f9d9d853d1fff68a8a25e64c7a8/clippy_utils/src/paths.rs) (after rust-lang/rust-clippy#7466) to get some feedback early on. I've also decided against adding diagnostic items to methods, as it would be nicer and more scalable to access them in a nicer fashion, like adding a `is_diagnostic_assoc_item(did, sym::Iterator, sym::map)` function or something similar (Suggested by `@camsteffen` [on Zulip](https://rust-lang.zulipchat.com/#narrow/stream/147480-t-compiler.2Fwg-diagnostics/topic/Diagnostic.20Item.20Naming.20Convention.3F/near/225024603))

There seems to be some different naming conventions when it comes to diagnostic items, some use UpperCamelCase (`BinaryHeap`) and some snake_case (`hashmap_type`). This PR uses UpperCamelCase for structs and traits and snake_case with the module name as a prefix for functions. Any feedback on is this welcome.

cc: rust-lang/rust-clippy#5393

r? `@Manishearth`

Author: JohnTitor

alloc/src/borrow.rs

@@ -177,6 +177,7 @@ where
 /// }
 /// ```
 #[stable(feature = "rust1", since = "1.0.0")]
+#[cfg_attr(not(test), rustc_diagnostic_item = "Cow")]
 pub enum Cow<'a, B: ?Sized + 'a>
 where
     B: ToOwned,

alloc/src/collections/btree/map/entry.rs

@@ -14,6 +14,7 @@ use Entry::*;
 ///
 /// [`entry`]: BTreeMap::entry
 #[stable(feature = "rust1", since = "1.0.0")]
+#[cfg_attr(not(test), rustc_diagnostic_item = "BTreeEntry")]
 pub enum Entry<'a, K: 'a, V: 'a> {
     /// A vacant entry.
     #[stable(feature = "rust1", since = "1.0.0")]

core/src/any.rs

@@ -108,6 +108,7 @@ use crate::intrinsics;
 // unsafe traits and unsafe methods (i.e., `type_id` would still be safe to call,
 // but we would likely want to indicate as such in documentation).
 #[stable(feature = "rust1", since = "1.0.0")]
+#[cfg_attr(not(test), rustc_diagnostic_item = "Any")]
 pub trait Any: 'static {
     /// Gets the `TypeId` of `self`.
     ///

core/src/cmp.rs

@@ -1104,6 +1104,7 @@ pub macro PartialOrd($item:item) {
 #[inline]
 #[must_use]
 #[stable(feature = "rust1", since = "1.0.0")]
+#[cfg_attr(not(test), rustc_diagnostic_item = "cmp_min")]
 pub fn min<T: Ord>(v1: T, v2: T) -> T {
     v1.min(v2)
 }
@@ -1166,6 +1167,7 @@ pub fn min_by_key<T, F: FnMut(&T) -> K, K: Ord>(v1: T, v2: T, mut f: F) -> T {
 #[inline]
 #[must_use]
 #[stable(feature = "rust1", since = "1.0.0")]
+#[cfg_attr(not(test), rustc_diagnostic_item = "cmp_max")]
 pub fn max<T: Ord>(v1: T, v2: T) -> T {
     v1.max(v2)
 }

core/src/convert/mod.rs

@@ -152,6 +152,7 @@ pub const fn identity<T>(x: T) -> T {
 /// is_hello(s);
 /// ```
 #[stable(feature = "rust1", since = "1.0.0")]
+#[cfg_attr(not(test), rustc_diagnostic_item = "AsRef")]
 pub trait AsRef<T: ?Sized> {
     /// Performs the conversion.
     #[stable(feature = "rust1", since = "1.0.0")]
@@ -193,6 +194,7 @@ pub trait AsRef<T: ?Sized> {
 ///
 /// [`Box<T>`]: ../../std/boxed/struct.Box.html
 #[stable(feature = "rust1", since = "1.0.0")]
+#[cfg_attr(not(test), rustc_diagnostic_item = "AsMut")]
 pub trait AsMut<T: ?Sized> {
     /// Performs the conversion.
     #[stable(feature = "rust1", since = "1.0.0")]

core/src/iter/sources/repeat.rs

@@ -51,6 +51,7 @@ use crate::iter::{FusedIterator, TrustedLen};
 /// ```
 #[inline]
 #[stable(feature = "rust1", since = "1.0.0")]
+#[cfg_attr(not(test), rustc_diagnostic_item = "iter_repeat")]
 pub fn repeat<T: Clone>(elt: T) -> Repeat<T> {
     Repeat { element: elt }
 }

core/src/iter/traits/double_ended.rs

@@ -36,6 +36,7 @@ use crate::ops::{ControlFlow, Try};
 /// assert_eq!(None, iter.next_back());
 /// ```
 #[stable(feature = "rust1", since = "1.0.0")]
+#[cfg_attr(not(test), rustc_diagnostic_item = "DoubleEndedIterator")]
 pub trait DoubleEndedIterator: Iterator {
     /// Removes and returns an element from the end of the iterator.
     ///

core/src/mem/mod.rs

@@ -140,6 +140,7 @@ pub use crate::intrinsics::transmute;
 #[inline]
 #[rustc_const_stable(feature = "const_forget", since = "1.46.0")]
 #[stable(feature = "rust1", since = "1.0.0")]
+#[cfg_attr(not(test), rustc_diagnostic_item = "mem_forget")]
 pub const fn forget<T>(t: T) {
     let _ = ManuallyDrop::new(t);
 }
@@ -298,6 +299,7 @@ pub fn forget_unsized<T: ?Sized>(t: T) {
 #[stable(feature = "rust1", since = "1.0.0")]
 #[rustc_promotable]
 #[rustc_const_stable(feature = "const_size_of", since = "1.24.0")]
+#[cfg_attr(not(test), rustc_diagnostic_item = "mem_size_of")]
 pub const fn size_of<T>() -> usize {
     intrinsics::size_of::<T>()
 }
@@ -324,6 +326,7 @@ pub const fn size_of<T>() -> usize {
 #[inline]
 #[stable(feature = "rust1", since = "1.0.0")]
 #[rustc_const_unstable(feature = "const_size_of_val", issue = "46571")]
+#[cfg_attr(not(test), rustc_diagnostic_item = "mem_size_of_val")]
 pub const fn size_of_val<T: ?Sized>(val: &T) -> usize {
     // SAFETY: `val` is a reference, so it's a valid raw pointer
     unsafe { intrinsics::size_of_val(val) }
@@ -814,6 +817,7 @@ pub fn take<T: Default>(dest: &mut T) -> T {
 #[stable(feature = "rust1", since = "1.0.0")]
 #[must_use = "if you don't need the old value, you can just assign the new value directly"]
 #[rustc_const_unstable(feature = "const_replace", issue = "83164")]
+#[cfg_attr(not(test), rustc_diagnostic_item = "mem_replace")]
 pub const fn replace<T>(dest: &mut T, src: T) -> T {
     // SAFETY: We read from `dest` but directly write `src` into it afterwards,
     // such that the old value is not duplicated. Nothing is dropped and
@@ -888,6 +892,7 @@ pub const fn replace<T>(dest: &mut T, src: T) -> T {
 /// [`RefCell`]: crate::cell::RefCell
 #[inline]
 #[stable(feature = "rust1", since = "1.0.0")]
+#[cfg_attr(not(test), rustc_diagnostic_item = "mem_drop")]
 pub fn drop<T>(_x: T) {}
 
 /// Interprets `src` as having type `&U`, and then reads `src` without moving
@@ -1015,6 +1020,7 @@ impl<T> fmt::Debug for Discriminant<T> {
 /// ```
 #[stable(feature = "discriminant_value", since = "1.21.0")]
 #[rustc_const_unstable(feature = "const_discriminant", issue = "69821")]
+#[cfg_attr(not(test), rustc_diagnostic_item = "mem_discriminant")]
 pub const fn discriminant<T>(v: &T) -> Discriminant<T> {
     Discriminant(intrinsics::discriminant_value(v))
 }

core/src/time.rs

@@ -61,6 +61,7 @@ const MICROS_PER_SEC: u64 = 1_000_000;
 /// crate to do so.
 #[stable(feature = "duration", since = "1.3.0")]
 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Default)]
+#[cfg_attr(not(test), rustc_diagnostic_item = "Duration")]
 pub struct Duration {
     secs: u64,
     nanos: u32, // Always 0 <= nanos < NANOS_PER_SEC

std/src/collections/hash/map.rs

@@ -1829,6 +1829,7 @@ impl<K, V, S> Debug for RawEntryBuilder<'_, K, V, S> {
 ///
 /// [`entry`]: HashMap::entry
 #[stable(feature = "rust1", since = "1.0.0")]
+#[cfg_attr(not(test), rustc_diagnostic_item = "HashMapEntry")]
 pub enum Entry<'a, K: 'a, V: 'a> {
     /// An occupied entry.
     #[stable(feature = "rust1", since = "1.0.0")]