Auto merge of #138114 - compiler-errors:rollup-7xr4b69, r=compiler-errors

Rollup of 25 pull requests

Successful merges:

 - #135733 (Implement `&pin const self` and `&pin mut self` sugars)
 - #135895 (Document workings of successors more clearly)
 - #136922 (Pattern types: Avoid having to handle an Option for range ends in the type system or the HIR)
 - #137303 (Remove `MaybeForgetReturn` suggestion)
 - #137327 (Undeprecate env::home_dir)
 - #137358 (Match Ergonomics 2024: add context and examples to the unstable book)
 - #137534 ([rustdoc] hide item that is not marked as doc(inline) and whose src is doc(hidden))
 - #137565 (Try to point of macro expansion from resolver and method errors if it involves macro var)
 - #137637 (Check dyn flavor before registering upcast goal on wide pointer cast in MIR typeck)
 - #137643 (Add DWARF test case for non-C-like `repr128` enums)
 - #137744 (Re-add `Clone`-derive on `Thir`)
 - #137758 (fix usage of ty decl macro fragments in attributes)
 - #137764 (Ensure that negative auto impls are always applicable)
 - #137772 (Fix char count in `Display` for `ByteStr`)
 - #137798 (ci: use ubuntu 24 on arm large runner)
 - #137802 (miri native-call support: all previously exposed provenance is accessible to the callee)
 - #137805 (adjust Layout debug printing to match the internal field name)
 - #137808 (Do not require that unsafe fields lack drop glue)
 - #137820 (Clarify why InhabitedPredicate::instantiate_opt exists)
 - #137825 (Provide more context on resolve error caused from incorrect RTN)
 - #137834 (rustc_fluent_macro: use CARGO_CRATE_NAME instead of CARGO_PKG_NAME)
 - #137868 (Add minimal platform support documentation for powerpc-unknown-linux-gnuspe)
 - #137910 (Improve error message for `AsyncFn` trait failure for RPIT)
 - #137920 (interpret/provenance_map: consistently use range_is_empty)
 - #138038 (Update `compiler-builtins` to 0.1.151)

r? `@ghost`
`@rustbot` modify labels: rollup

1 files changed, 42 insertions, 20 deletions

diff --git a/compiler/rustc_parse/src/parser/item.rs b/compiler/rustc_parse/src/parser/item.rs
index 3f642a7ac1f..c3b1956ad2e 100644
--- a/compiler/rustc_parse/src/parser/item.rs
+++ b/compiler/rustc_parse/src/parser/item.rs
@@ -2954,14 +2954,27 @@ impl<'a> Parser<'a> {
             }
             _ => unreachable!(),
         };
+        // is lifetime `n` tokens ahead?
+        let is_lifetime = |this: &Self, n| this.look_ahead(n, |t| t.is_lifetime());
         // Is `self` `n` tokens ahead?
         let is_isolated_self = |this: &Self, n| {
             this.is_keyword_ahead(n, &[kw::SelfLower])
                 && this.look_ahead(n + 1, |t| t != &token::PathSep)
         };
+        // Is `pin const self` `n` tokens ahead?
+        let is_isolated_pin_const_self = |this: &Self, n| {
+            this.look_ahead(n, |token| token.is_ident_named(sym::pin))
+                && this.is_keyword_ahead(n + 1, &[kw::Const])
+                && is_isolated_self(this, n + 2)
+        };
         // Is `mut self` `n` tokens ahead?
         let is_isolated_mut_self =
             |this: &Self, n| this.is_keyword_ahead(n, &[kw::Mut]) && is_isolated_self(this, n + 1);
+        // Is `pin mut self` `n` tokens ahead?
+        let is_isolated_pin_mut_self = |this: &Self, n| {
+            this.look_ahead(n, |token| token.is_ident_named(sym::pin))
+                && is_isolated_mut_self(this, n + 1)
+        };
         // Parse `self` or `self: TYPE`. We already know the current token is `self`.
         let parse_self_possibly_typed = |this: &mut Self, m| {
             let eself_ident = expect_self_ident(this);
@@ -3012,26 +3025,35 @@ impl<'a> Parser<'a> {
         let eself_lo = self.token.span;
         let (eself, eself_ident, eself_hi) = match self.token.uninterpolate().kind {
             token::And => {
-                let eself = if is_isolated_self(self, 1) {
-                    // `&self`
-                    self.bump();
-                    SelfKind::Region(None, Mutability::Not)
-                } else if is_isolated_mut_self(self, 1) {
-                    // `&mut self`
-                    self.bump();
-                    self.bump();
-                    SelfKind::Region(None, Mutability::Mut)
-                } else if self.look_ahead(1, |t| t.is_lifetime()) && is_isolated_self(self, 2) {
-                    // `&'lt self`
-                    self.bump();
-                    let lt = self.expect_lifetime();
-                    SelfKind::Region(Some(lt), Mutability::Not)
-                } else if self.look_ahead(1, |t| t.is_lifetime()) && is_isolated_mut_self(self, 2) {
-                    // `&'lt mut self`
-                    self.bump();
-                    let lt = self.expect_lifetime();
-                    self.bump();
-                    SelfKind::Region(Some(lt), Mutability::Mut)
+                let has_lifetime = is_lifetime(self, 1);
+                let skip_lifetime_count = has_lifetime as usize;
+                let eself = if is_isolated_self(self, skip_lifetime_count + 1) {
+                    // `&{'lt} self`
+                    self.bump(); // &
+                    let lifetime = has_lifetime.then(|| self.expect_lifetime());
+                    SelfKind::Region(lifetime, Mutability::Not)
+                } else if is_isolated_mut_self(self, skip_lifetime_count + 1) {
+                    // `&{'lt} mut self`
+                    self.bump(); // &
+                    let lifetime = has_lifetime.then(|| self.expect_lifetime());
+                    self.bump(); // mut
+                    SelfKind::Region(lifetime, Mutability::Mut)
+                } else if is_isolated_pin_const_self(self, skip_lifetime_count + 1) {
+                    // `&{'lt} pin const self`
+                    self.bump(); // &
+                    let lifetime = has_lifetime.then(|| self.expect_lifetime());
+                    self.psess.gated_spans.gate(sym::pin_ergonomics, self.token.span);
+                    self.bump(); // pin
+                    self.bump(); // const
+                    SelfKind::Pinned(lifetime, Mutability::Not)
+                } else if is_isolated_pin_mut_self(self, skip_lifetime_count + 1) {
+                    // `&{'lt} pin mut self`
+                    self.bump(); // &
+                    let lifetime = has_lifetime.then(|| self.expect_lifetime());
+                    self.psess.gated_spans.gate(sym::pin_ergonomics, self.token.span);
+                    self.bump(); // pin
+                    self.bump(); // mut
+                    SelfKind::Pinned(lifetime, Mutability::Mut)
                 } else {
                     // `&not_self`
                     return Ok(None);