Merge pull request rust-lang#4095 from rust-lang/rustup-2024-12-15

Automatic Rustup

Author: oli-obk

Cargo.lock

@@ -3507,7 +3507,6 @@ dependencies = [
  "cc",
  "either",
  "itertools",
- "jobserver",
  "libc",
  "object 0.36.5",
  "pathdiff",

compiler/rustc_ast/src/ast.rs

@@ -1382,6 +1382,7 @@ impl Expr {
             | ExprKind::Tup(_)
             | ExprKind::Type(..)
             | ExprKind::Underscore
+            | ExprKind::UnsafeBinderCast(..)
             | ExprKind::While(..)
             | ExprKind::Err(_)
             | ExprKind::Dummy => ExprPrecedence::Unambiguous,
@@ -1509,7 +1510,13 @@ pub enum ExprKind {
     /// `'label: for await? pat in iter { block }`
     ///
     /// This is desugared to a combination of `loop` and `match` expressions.
-    ForLoop { pat: P<Pat>, iter: P<Expr>, body: P<Block>, label: Option<Label>, kind: ForLoopKind },
+    ForLoop {
+        pat: P<Pat>,
+        iter: P<Expr>,
+        body: P<Block>,
+        label: Option<Label>,
+        kind: ForLoopKind,
+    },
     /// Conditionless loop (can be exited with `break`, `continue`, or `return`).
     ///
     /// `'label: loop { block }`
@@ -1614,6 +1621,8 @@ pub enum ExprKind {
     /// A `format_args!()` expression.
     FormatArgs(P<FormatArgs>),
 
+    UnsafeBinderCast(UnsafeBinderCastKind, P<Expr>, Option<P<Ty>>),
+
     /// Placeholder for an expression that wasn't syntactically well formed in some way.
     Err(ErrorGuaranteed),
 
@@ -1652,6 +1661,16 @@ impl GenBlockKind {
     }
 }
 
+/// Whether we're unwrapping or wrapping an unsafe binder
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+#[derive(Encodable, Decodable, HashStable_Generic)]
+pub enum UnsafeBinderCastKind {
+    // e.g. `&i32` -> `unsafe<'a> &'a i32`
+    Wrap,
+    // e.g. `unsafe<'a> &'a i32` -> `&i32`
+    Unwrap,
+}
+
 /// The explicit `Self` type in a "qualified path". The actual
 /// path, including the trait and the associated item, is stored
 /// separately. `position` represents the index of the associated
@@ -2223,6 +2242,12 @@ pub struct BareFnTy {
     pub decl_span: Span,
 }
 
+#[derive(Clone, Encodable, Decodable, Debug)]
+pub struct UnsafeBinderTy {
+    pub generic_params: ThinVec<GenericParam>,
+    pub inner_ty: P<Ty>,
+}
+
 /// The various kinds of type recognized by the compiler.
 //
 // Adding a new variant? Please update `test_ty` in `tests/ui/macros/stringify.rs`.
@@ -2242,6 +2267,8 @@ pub enum TyKind {
     PinnedRef(Option<Lifetime>, MutTy),
     /// A bare function (e.g., `fn(usize) -> bool`).
     BareFn(P<BareFnTy>),
+    /// An unsafe existential lifetime binder (e.g., `unsafe<'a> &'a ()`).
+    UnsafeBinder(P<UnsafeBinderTy>),
     /// The never type (`!`).
     Never,
     /// A tuple (`(A, B, C, D,...)`).
@@ -2877,7 +2904,7 @@ pub enum ModKind {
     /// or with definition outlined to a separate file `mod foo;` and already loaded from it.
     /// The inner span is from the first token past `{` to the last token until `}`,
     /// or from the first to the last token in the loaded file.
-    Loaded(ThinVec<P<Item>>, Inline, ModSpans),
+    Loaded(ThinVec<P<Item>>, Inline, ModSpans, Result<(), ErrorGuaranteed>),
     /// Module with definition outlined to a separate file `mod foo;` but not yet loaded from it.
     Unloaded,
 }

compiler/rustc_ast/src/mut_visit.rs

@@ -558,6 +558,11 @@ pub fn walk_ty<T: MutVisitor>(vis: &mut T, ty: &mut P<Ty>) {
             vis.visit_fn_decl(decl);
             vis.visit_span(decl_span);
         }
+        TyKind::UnsafeBinder(binder) => {
+            let UnsafeBinderTy { generic_params, inner_ty } = binder.deref_mut();
+            generic_params.flat_map_in_place(|param| vis.flat_map_generic_param(param));
+            vis.visit_ty(inner_ty);
+        }
         TyKind::Tup(tys) => visit_thin_vec(tys, |ty| vis.visit_ty(ty)),
         TyKind::Paren(ty) => vis.visit_ty(ty),
         TyKind::Pat(ty, pat) => {
@@ -1212,7 +1217,12 @@ impl WalkItemKind for ItemKind {
             ItemKind::Mod(safety, mod_kind) => {
                 visit_safety(vis, safety);
                 match mod_kind {
-                    ModKind::Loaded(items, _inline, ModSpans { inner_span, inject_use_span }) => {
+                    ModKind::Loaded(
+                        items,
+                        _inline,
+                        ModSpans { inner_span, inject_use_span },
+                        _,
+                    ) => {
                         items.flat_map_in_place(|item| vis.flat_map_item(item));
                         vis.visit_span(inner_span);
                         vis.visit_span(inject_use_span);
@@ -1775,6 +1785,12 @@ pub fn walk_expr<T: MutVisitor>(vis: &mut T, Expr { kind, id, span, attrs, token
         ExprKind::TryBlock(body) => vis.visit_block(body),
         ExprKind::Lit(_token) => {}
         ExprKind::IncludedBytes(_bytes) => {}
+        ExprKind::UnsafeBinderCast(_kind, expr, ty) => {
+            vis.visit_expr(expr);
+            if let Some(ty) = ty {
+                vis.visit_ty(ty);
+            }
+        }
         ExprKind::Err(_guar) => {}
         ExprKind::Dummy => {}
     }

compiler/rustc_ast/src/util/classify.rs

@@ -152,6 +152,7 @@ pub fn leading_labeled_expr(mut expr: &ast::Expr) -> bool {
             | Underscore
             | Yeet(..)
             | Yield(..)
+            | UnsafeBinderCast(..)
             | Err(..)
             | Dummy => return false,
         }
@@ -232,6 +233,7 @@ pub fn expr_trailing_brace(mut expr: &ast::Expr) -> Option<TrailingBrace<'_>> {
             | Paren(_)
             | Try(_)
             | Yeet(None)
+            | UnsafeBinderCast(..)
             | Err(_)
             | Dummy => break None,
         }
@@ -253,6 +255,10 @@ fn type_trailing_braced_mac_call(mut ty: &ast::Ty) -> Option<&ast::MacCall> {
                 ty = &mut_ty.ty;
             }
 
+            ast::TyKind::UnsafeBinder(binder) => {
+                ty = &binder.inner_ty;
+            }
+
             ast::TyKind::BareFn(fn_ty) => match &fn_ty.decl.output {
                 ast::FnRetTy::Default(_) => break None,
                 ast::FnRetTy::Ty(ret) => ty = ret,

compiler/rustc_ast/src/visit.rs

@@ -380,7 +380,7 @@ impl WalkItemKind for ItemKind {
                 try_visit!(visitor.visit_fn(kind, span, id));
             }
             ItemKind::Mod(_unsafety, mod_kind) => match mod_kind {
-                ModKind::Loaded(items, _inline, _inner_span) => {
+                ModKind::Loaded(items, _inline, _inner_span, _) => {
                     walk_list!(visitor, visit_item, items);
                 }
                 ModKind::Unloaded => {}
@@ -522,6 +522,10 @@ pub fn walk_ty<'a, V: Visitor<'a>>(visitor: &mut V, typ: &'a Ty) -> V::Result {
             walk_list!(visitor, visit_generic_param, generic_params);
             try_visit!(visitor.visit_fn_decl(decl));
         }
+        TyKind::UnsafeBinder(binder) => {
+            walk_list!(visitor, visit_generic_param, &binder.generic_params);
+            try_visit!(visitor.visit_ty(&binder.inner_ty));
+        }
         TyKind::Path(maybe_qself, path) => {
             try_visit!(visitor.visit_qself(maybe_qself));
             try_visit!(visitor.visit_path(path, *id));
@@ -1226,6 +1230,10 @@ pub fn walk_expr<'a, V: Visitor<'a>>(visitor: &mut V, expression: &'a Expr) -> V
         ExprKind::TryBlock(body) => try_visit!(visitor.visit_block(body)),
         ExprKind::Lit(_token) => {}
         ExprKind::IncludedBytes(_bytes) => {}
+        ExprKind::UnsafeBinderCast(_kind, expr, ty) => {
+            try_visit!(visitor.visit_expr(expr));
+            visit_opt!(visitor, visit_ty, ty);
+        }
         ExprKind::Err(_guar) => {}
         ExprKind::Dummy => {}
     }

compiler/rustc_ast_lowering/src/block.rs

@@ -1,5 +1,6 @@
 use rustc_ast::{Block, BlockCheckMode, Local, LocalKind, Stmt, StmtKind};
 use rustc_hir as hir;
+use rustc_span::sym;
 use smallvec::SmallVec;
 
 use crate::{ImplTraitContext, ImplTraitPosition, LoweringContext};
@@ -82,11 +83,21 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         (self.arena.alloc_from_iter(stmts), expr)
     }
 
+    /// Return an `ImplTraitContext` that allows impl trait in bindings if
+    /// the feature gate is enabled, or issues a feature error if it is not.
+    fn impl_trait_in_bindings_ctxt(&self, position: ImplTraitPosition) -> ImplTraitContext {
+        if self.tcx.features().impl_trait_in_bindings() {
+            ImplTraitContext::InBinding
+        } else {
+            ImplTraitContext::FeatureGated(position, sym::impl_trait_in_bindings)
+        }
+    }
+
     fn lower_local(&mut self, l: &Local) -> &'hir hir::LetStmt<'hir> {
-        let ty = l
-            .ty
-            .as_ref()
-            .map(|t| self.lower_ty(t, ImplTraitContext::Disallowed(ImplTraitPosition::Variable)));
+        // Let statements are allowed to have impl trait in bindings.
+        let ty = l.ty.as_ref().map(|t| {
+            self.lower_ty(t, self.impl_trait_in_bindings_ctxt(ImplTraitPosition::Variable))
+        });
         let init = l.kind.init().map(|init| self.lower_expr(init));
         let hir_id = self.lower_node_id(l.id);
         let pat = self.lower_pat(&l.pat);

compiler/rustc_ast_lowering/src/expr.rs

@@ -379,6 +379,14 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 ExprKind::Yield(opt_expr) => self.lower_expr_yield(e.span, opt_expr.as_deref()),
                 ExprKind::Err(guar) => hir::ExprKind::Err(*guar),
 
+                ExprKind::UnsafeBinderCast(kind, expr, ty) => hir::ExprKind::UnsafeBinderCast(
+                    *kind,
+                    self.lower_expr(expr),
+                    ty.as_ref().map(|ty| {
+                        self.lower_ty(ty, ImplTraitContext::Disallowed(ImplTraitPosition::Cast))
+                    }),
+                ),
+
                 ExprKind::Dummy => {
                     span_bug!(e.span, "lowered ExprKind::Dummy")
                 }

compiler/rustc_ast_lowering/src/item.rs

@@ -238,7 +238,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 })
             }
             ItemKind::Mod(_, mod_kind) => match mod_kind {
-                ModKind::Loaded(items, _, spans) => {
+                ModKind::Loaded(items, _, spans, _) => {
                     hir::ItemKind::Mod(self.lower_mod(items, spans))
                 }
                 ModKind::Unloaded => panic!("`mod` items should have been loaded by now"),

compiler/rustc_ast_lowering/src/lib.rs

@@ -260,6 +260,13 @@ enum ImplTraitContext {
     /// equivalent to a new opaque type like `type T = impl Debug; fn foo() -> T`.
     ///
     OpaqueTy { origin: hir::OpaqueTyOrigin<LocalDefId> },
+
+    /// Treat `impl Trait` as a "trait ascription", which is like a type
+    /// variable but that also enforces that a set of trait goals hold.
+    ///
+    /// This is useful to guide inference for unnameable types.
+    InBinding,
+
     /// `impl Trait` is unstably accepted in this position.
     FeatureGated(ImplTraitPosition, Symbol),
     /// `impl Trait` is not accepted in this position.
@@ -1228,6 +1235,13 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                     param_names: self.lower_fn_params_to_names(&f.decl),
                 }))
             }
+            TyKind::UnsafeBinder(f) => {
+                let generic_params = self.lower_lifetime_binder(t.id, &f.generic_params);
+                hir::TyKind::UnsafeBinder(self.arena.alloc(hir::UnsafeBinderTy {
+                    generic_params,
+                    inner_ty: self.lower_ty(&f.inner_ty, itctx),
+                }))
+            }
             TyKind::Never => hir::TyKind::Never,
             TyKind::Tup(tys) => hir::TyKind::Tup(
                 self.arena.alloc_from_iter(tys.iter().map(|ty| self.lower_ty_direct(ty, itctx))),
@@ -1320,6 +1334,9 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                         }
                         path
                     }
+                    ImplTraitContext::InBinding => {
+                        hir::TyKind::TraitAscription(self.lower_param_bounds(bounds, itctx))
+                    }
                     ImplTraitContext::FeatureGated(position, feature) => {
                         let guar = self
                             .tcx

compiler/rustc_ast_passes/src/ast_validation.rs

@@ -1029,7 +1029,7 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                     self.dcx().emit_err(errors::UnsafeItem { span, kind: "module" });
                 }
                 // Ensure that `path` attributes on modules are recorded as used (cf. issue #35584).
-                if !matches!(mod_kind, ModKind::Loaded(_, Inline::Yes, _))
+                if !matches!(mod_kind, ModKind::Loaded(_, Inline::Yes, _, _))
                     && !attr::contains_name(&item.attrs, sym::path)
                 {
                     self.check_mod_file_item_asciionly(item.ident);