Auto merge of #75145 - davidtwco:issue-60607-preallocate-defid-for-lang-items, r=petrochenkov

Reference lang items during AST lowering

Fixes #60607 and fixes #61019.

This PR introduces `QPath::LangItem` to the HIR and uses it in AST lowering instead of constructing a `hir::Path` from a slice of symbols:

- Credit for much of this work goes to @matthewjasper, I basically just [rebased their earlier work](matthewjasper@a227c70#diff-c0f791ead38d2d02916faaad0f56f41d).
- ~~Changes to Clippy might not be correct, they compile but attempting to run tests through `./x.py` produced failures which appeared spurious, so I didn't run any clippy tests.~~
- Changes to save analysis might not be correct - tests pass but I don't have a lot of confidence in those changes being correct.
- I've used `GenericBounds::LangItemTrait` rather than changing `PolyTraitRef`, as suggested by @matthewjasper [in this comment](matthewjasper@a227c70#r40107992) but I'd prefer that be left for a follow-up.
- I've split things into smaller commits fairly arbitrarily to make the diff easier to review, each commit should compile but might not pass tests until the final commit.

r? @oli-obk
cc @matthewjasper

Author: bors

Diff for: library/core/src/convert/mod.rs

@@ -385,6 +385,7 @@ pub trait Into<T>: Sized {
 ))]
 pub trait From<T>: Sized {
     /// Performs the conversion.
+    #[cfg_attr(not(bootstrap), lang = "from")]
     #[stable(feature = "rust1", since = "1.0.0")]
     fn from(_: T) -> Self;
 }

Diff for: library/core/src/future/future.rs

@@ -96,6 +96,7 @@ pub trait Future {
     /// [`Context`]: ../task/struct.Context.html
     /// [`Waker`]: ../task/struct.Waker.html
     /// [`Waker::wake`]: ../task/struct.Waker.html#method.wake
+    #[cfg_attr(not(bootstrap), lang = "poll")]
     #[stable(feature = "futures_api", since = "1.36.0")]
     fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output>;
 }

Diff for: library/core/src/future/mod.rs

@@ -53,6 +53,7 @@ unsafe impl Sync for ResumeTy {}
 /// This function returns a `GenFuture` underneath, but hides it in `impl Trait` to give
 /// better error messages (`impl Future` rather than `GenFuture<[closure.....]>`).
 // This is `const` to avoid extra errors after we recover from `const async fn`
+#[cfg_attr(not(bootstrap), lang = "from_generator")]
 #[doc(hidden)]
 #[unstable(feature = "gen_future", issue = "50547")]
 #[inline]
@@ -85,6 +86,7 @@ where
     GenFuture(gen)
 }
 
+#[cfg_attr(not(bootstrap), lang = "get_context")]
 #[doc(hidden)]
 #[unstable(feature = "gen_future", issue = "50547")]
 #[inline]

Diff for: library/core/src/iter/traits/collect.rs

@@ -235,6 +235,7 @@ pub trait IntoIterator {
     /// assert_eq!(Some(3), iter.next());
     /// assert_eq!(None, iter.next());
     /// ```
+    #[cfg_attr(not(bootstrap), lang = "into_iter")]
     #[stable(feature = "rust1", since = "1.0.0")]
     fn into_iter(self) -> Self::IntoIter;
 }

Diff for: library/core/src/iter/traits/iterator.rs

@@ -129,6 +129,7 @@ pub trait Iterator {
     /// assert_eq!(None, iter.next());
     /// assert_eq!(None, iter.next());
     /// ```
+    #[cfg_attr(not(bootstrap), lang = "next")]
     #[stable(feature = "rust1", since = "1.0.0")]
     fn next(&mut self) -> Option<Self::Item>;
 

Diff for: library/core/src/ops/range.rs

@@ -38,6 +38,7 @@ use crate::hash::Hash;
 /// [`IntoIterator`]: ../iter/trait.Iterator.html
 /// [`Iterator`]: ../iter/trait.IntoIterator.html
 /// [slicing index]: ../slice/trait.SliceIndex.html
+#[cfg_attr(not(bootstrap), lang = "RangeFull")]
 #[doc(alias = "..")]
 #[derive(Copy, Clone, Default, PartialEq, Eq, Hash)]
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -70,6 +71,7 @@ impl fmt::Debug for RangeFull {
 /// assert_eq!(arr[1.. 3], [  1,2    ]);  // Range
 /// assert_eq!(arr[1..=3], [  1,2,3  ]);
 /// ```
+#[cfg_attr(not(bootstrap), lang = "Range")]
 #[doc(alias = "..")]
 #[derive(Clone, Default, PartialEq, Eq, Hash)] // not Copy -- see #27186
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -178,6 +180,7 @@ impl<Idx: PartialOrd<Idx>> Range<Idx> {
 /// ```
 ///
 /// [`Iterator`]: ../iter/trait.IntoIterator.html
+#[cfg_attr(not(bootstrap), lang = "RangeFrom")]
 #[doc(alias = "..")]
 #[derive(Clone, PartialEq, Eq, Hash)] // not Copy -- see #27186
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -260,6 +263,7 @@ impl<Idx: PartialOrd<Idx>> RangeFrom<Idx> {
 /// [`IntoIterator`]: ../iter/trait.Iterator.html
 /// [`Iterator`]: ../iter/trait.IntoIterator.html
 /// [slicing index]: ../slice/trait.SliceIndex.html
+#[cfg_attr(not(bootstrap), lang = "RangeTo")]
 #[doc(alias = "..")]
 #[derive(Copy, Clone, PartialEq, Eq, Hash)]
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -328,6 +332,7 @@ impl<Idx: PartialOrd<Idx>> RangeTo<Idx> {
 /// assert_eq!(arr[1.. 3], [  1,2    ]);
 /// assert_eq!(arr[1..=3], [  1,2,3  ]);  // RangeInclusive
 /// ```
+#[cfg_attr(not(bootstrap), lang = "RangeInclusive")]
 #[doc(alias = "..=")]
 #[derive(Clone, PartialEq, Eq, Hash)] // not Copy -- see #27186
 #[stable(feature = "inclusive_range", since = "1.26.0")]
@@ -359,6 +364,7 @@ impl<Idx> RangeInclusive<Idx> {
     ///
     /// assert_eq!(3..=5, RangeInclusive::new(3, 5));
     /// ```
+    #[cfg_attr(not(bootstrap), lang = "range_inclusive_new")]
     #[stable(feature = "inclusive_range_methods", since = "1.27.0")]
     #[inline]
     #[rustc_promotable]
@@ -555,6 +561,7 @@ impl<Idx: PartialOrd<Idx>> RangeInclusive<Idx> {
 /// [`IntoIterator`]: ../iter/trait.Iterator.html
 /// [`Iterator`]: ../iter/trait.IntoIterator.html
 /// [slicing index]: ../slice/trait.SliceIndex.html
+#[cfg_attr(not(bootstrap), lang = "RangeToInclusive")]
 #[doc(alias = "..=")]
 #[derive(Copy, Clone, PartialEq, Eq, Hash)]
 #[stable(feature = "inclusive_range", since = "1.26.0")]

Diff for: library/core/src/ops/try.rs

@@ -43,16 +43,19 @@ pub trait Try {
     /// in the return type of the enclosing scope (which must itself implement
     /// `Try`). Specifically, the value `X::from_error(From::from(e))`
     /// is returned, where `X` is the return type of the enclosing function.
+    #[cfg_attr(not(bootstrap), lang = "into_result")]
     #[unstable(feature = "try_trait", issue = "42327")]
     fn into_result(self) -> Result<Self::Ok, Self::Error>;
 
     /// Wrap an error value to construct the composite result. For example,
     /// `Result::Err(x)` and `Result::from_error(x)` are equivalent.
+    #[cfg_attr(not(bootstrap), lang = "from_error")]
     #[unstable(feature = "try_trait", issue = "42327")]
     fn from_error(v: Self::Error) -> Self;
 
     /// Wrap an OK value to construct the composite result. For example,
     /// `Result::Ok(x)` and `Result::from_ok(x)` are equivalent.
+    #[cfg_attr(not(bootstrap), lang = "from_ok")]
     #[unstable(feature = "try_trait", issue = "42327")]
     fn from_ok(v: Self::Ok) -> Self;
 }

Diff for: library/core/src/option.rs

@@ -144,9 +144,11 @@ use crate::{
 #[stable(feature = "rust1", since = "1.0.0")]
 pub enum Option<T> {
     /// No value
+    #[cfg_attr(not(bootstrap), lang = "None")]
     #[stable(feature = "rust1", since = "1.0.0")]
     None,
     /// Some value `T`
+    #[cfg_attr(not(bootstrap), lang = "Some")]
     #[stable(feature = "rust1", since = "1.0.0")]
     Some(#[stable(feature = "rust1", since = "1.0.0")] T),
 }

Diff for: library/core/src/pin.rs

@@ -569,6 +569,7 @@ impl<P: Deref> Pin<P> {
     ///  ```
     ///
     /// [`mem::swap`]: ../../std/mem/fn.swap.html
+    #[cfg_attr(not(bootstrap), lang = "new_unchecked")]
     #[stable(feature = "pin", since = "1.33.0")]
     #[inline(always)]
     pub unsafe fn new_unchecked(pointer: P) -> Pin<P> {

Diff for: library/core/src/result.rs

@@ -246,10 +246,12 @@ use crate::{convert, fmt};
 #[stable(feature = "rust1", since = "1.0.0")]
 pub enum Result<T, E> {
     /// Contains the success value
+    #[cfg_attr(not(bootstrap), lang = "Ok")]
     #[stable(feature = "rust1", since = "1.0.0")]
     Ok(#[stable(feature = "rust1", since = "1.0.0")] T),
 
     /// Contains the error value
+    #[cfg_attr(not(bootstrap), lang = "Err")]
     #[stable(feature = "rust1", since = "1.0.0")]
     Err(#[stable(feature = "rust1", since = "1.0.0")] E),
 }

Diff for: library/core/src/task/poll.rs

@@ -10,6 +10,7 @@ use crate::result::Result;
 #[stable(feature = "futures_api", since = "1.36.0")]
 pub enum Poll<T> {
     /// Represents that a value is immediately ready.
+    #[cfg_attr(not(bootstrap), lang = "Ready")]
     #[stable(feature = "futures_api", since = "1.36.0")]
     Ready(#[stable(feature = "futures_api", since = "1.36.0")] T),
 
@@ -18,6 +19,7 @@ pub enum Poll<T> {
     /// When a function returns `Pending`, the function *must* also
     /// ensure that the current task is scheduled to be awoken when
     /// progress can be made.
+    #[cfg_attr(not(bootstrap), lang = "Pending")]
     #[stable(feature = "futures_api", since = "1.36.0")]
     Pending,
 }