Rollup of 6 pull requests

compiler/rustc_codegen_ssa/src/back/link.rs

@@ -40,7 +40,6 @@ use regex::Regex;
 use tempfile::Builder as TempFileBuilder;
 
 use itertools::Itertools;
-use std::borrow::Borrow;
 use std::cell::OnceCell;
 use std::collections::BTreeSet;
 use std::ffi::OsString;
@@ -576,17 +575,17 @@ fn link_dwarf_object<'a>(
 
     impl<Relocations> ThorinSession<Relocations> {
         fn alloc_mmap(&self, data: Mmap) -> &Mmap {
-            (*self.arena_mmap.alloc(data)).borrow()
+            &*self.arena_mmap.alloc(data)
         }
     }
 
     impl<Relocations> thorin::Session<Relocations> for ThorinSession<Relocations> {
         fn alloc_data(&self, data: Vec<u8>) -> &[u8] {
-            (*self.arena_data.alloc(data)).borrow()
+            &*self.arena_data.alloc(data)
         }
 
         fn alloc_relocation(&self, data: Relocations) -> &Relocations {
-            (*self.arena_relocations.alloc(data)).borrow()
+            &*self.arena_relocations.alloc(data)
         }
 
         fn read_input(&self, path: &Path) -> std::io::Result<&[u8]> {

compiler/rustc_lint/messages.ftl

@@ -50,6 +50,14 @@ lint_deprecated_lint_name =
 lint_renamed_or_removed_lint = {$msg}
     .suggestion = use the new name
 
+lint_suspicious_double_ref_op =
+    using `.{$call}()` on a double reference, which returns `{$ty}` instead of {$op ->
+        *[should_not_happen] [{$op}]
+        [deref] dereferencing
+        [borrow] borrowing
+        [clone] cloning
+    } the inner type
+
 lint_unknown_lint =
     unknown lint: `{$name}`
     .suggestion = did you mean

compiler/rustc_lint/src/lints.rs

@@ -1150,6 +1150,14 @@ pub struct NoopMethodCallDiag<'a> {
     pub label: Span,
 }
 
+#[derive(LintDiagnostic)]
+#[diag(lint_suspicious_double_ref_op)]
+pub struct SuspiciousDoubleRefDiag<'a> {
+    pub call: Symbol,
+    pub ty: Ty<'a>,
+    pub op: &'static str,
+}
+
 // pass_by_value.rs
 #[derive(LintDiagnostic)]
 #[diag(lint_pass_by_value)]

compiler/rustc_lint/src/noop_method_call.rs

@@ -1,10 +1,11 @@
 use crate::context::LintContext;
-use crate::lints::NoopMethodCallDiag;
+use crate::lints::{NoopMethodCallDiag, SuspiciousDoubleRefDiag};
 use crate::LateContext;
 use crate::LateLintPass;
 use rustc_hir::def::DefKind;
 use rustc_hir::{Expr, ExprKind};
 use rustc_middle::ty;
+use rustc_middle::ty::adjustment::Adjust;
 use rustc_span::symbol::sym;
 
 declare_lint! {
@@ -35,14 +36,44 @@ declare_lint! {
     "detects the use of well-known noop methods"
 }
 
-declare_lint_pass!(NoopMethodCall => [NOOP_METHOD_CALL]);
+declare_lint! {
+    /// The `suspicious_double_ref_op` lint checks for usage of `.clone()`/`.borrow()`/`.deref()`
+    /// on an `&&T` when `T: !Deref/Borrow/Clone`, which means the call will return the inner `&T`,
+    /// instead of performing the operation on the underlying `T` and can be confusing.
+    ///
+    /// ### Example
+    ///
+    /// ```rust
+    /// # #![allow(unused)]
+    /// struct Foo;
+    /// let foo = &&Foo;
+    /// let clone: &Foo = foo.clone();
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// Since `Foo` doesn't implement `Clone`, running `.clone()` only dereferences the double
+    /// reference, instead of cloning the inner type which should be what was intended.
+    pub SUSPICIOUS_DOUBLE_REF_OP,
+    Warn,
+    "suspicious call of trait method on `&&T`"
+}
+
+declare_lint_pass!(NoopMethodCall => [NOOP_METHOD_CALL, SUSPICIOUS_DOUBLE_REF_OP]);
 
 impl<'tcx> LateLintPass<'tcx> for NoopMethodCall {
     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
         // We only care about method calls.
-        let ExprKind::MethodCall(call, receiver, ..) = &expr.kind else {
-            return
+        let ExprKind::MethodCall(call, receiver, _, call_span) = &expr.kind else {
+            return;
         };
+
+        if call_span.from_expansion() {
+            return;
+        }
+
         // We only care about method calls corresponding to the `Clone`, `Deref` and `Borrow`
         // traits and ignore any other method call.
         let did = match cx.typeck_results().type_dependent_def(expr.hir_id) {
@@ -70,25 +101,39 @@ impl<'tcx> LateLintPass<'tcx> for NoopMethodCall {
         };
         // (Re)check that it implements the noop diagnostic.
         let Some(name) = cx.tcx.get_diagnostic_name(i.def_id()) else { return };
-        if !matches!(
-            name,
-            sym::noop_method_borrow | sym::noop_method_clone | sym::noop_method_deref
-        ) {
-            return;
-        }
+
+        let op = match name {
+            sym::noop_method_borrow => "borrow",
+            sym::noop_method_clone => "clone",
+            sym::noop_method_deref => "deref",
+            _ => return,
+        };
+
         let receiver_ty = cx.typeck_results().expr_ty(receiver);
         let expr_ty = cx.typeck_results().expr_ty_adjusted(expr);
-        if receiver_ty != expr_ty {
-            // This lint will only trigger if the receiver type and resulting expression \
-            // type are the same, implying that the method call is unnecessary.
+        let arg_adjustments = cx.typeck_results().expr_adjustments(receiver);
+
+        // If there is any user defined auto-deref step, then we don't want to warn.
+        // https://github.com/rust-lang/rust-clippy/issues/9272
+        if arg_adjustments.iter().any(|adj| matches!(adj.kind, Adjust::Deref(Some(_)))) {
             return;
         }
+
         let expr_span = expr.span;
         let span = expr_span.with_lo(receiver.span.hi());
-        cx.emit_spanned_lint(
-            NOOP_METHOD_CALL,
-            span,
-            NoopMethodCallDiag { method: call.ident.name, receiver_ty, label: span },
-        );
+
+        if receiver_ty == expr_ty {
+            cx.emit_spanned_lint(
+                NOOP_METHOD_CALL,
+                span,
+                NoopMethodCallDiag { method: call.ident.name, receiver_ty, label: span },
+            );
+        } else {
+            cx.emit_spanned_lint(
+                SUSPICIOUS_DOUBLE_REF_OP,
+                span,
+                SuspiciousDoubleRefDiag { call: call.ident.name, ty: expr_ty, op },
+            )
+        }
     }
 }

library/alloc/src/boxed.rs

@@ -1455,9 +1455,36 @@ where
     }
 }
 
+/// Specialization trait used for `From<&[T]>`.
+#[cfg(not(no_global_oom_handling))]
+trait BoxFromSlice<T> {
+    fn from_slice(slice: &[T]) -> Self;
+}
+
+#[cfg(not(no_global_oom_handling))]
+impl<T: Clone> BoxFromSlice<T> for Box<[T]> {
+    #[inline]
+    default fn from_slice(slice: &[T]) -> Self {
+        slice.to_vec().into_boxed_slice()
+    }
+}
+
+#[cfg(not(no_global_oom_handling))]
+impl<T: Copy> BoxFromSlice<T> for Box<[T]> {
+    #[inline]
+    fn from_slice(slice: &[T]) -> Self {
+        let len = slice.len();
+        let buf = RawVec::with_capacity(len);
+        unsafe {
+            ptr::copy_nonoverlapping(slice.as_ptr(), buf.ptr(), len);
+            buf.into_box(slice.len()).assume_init()
+        }
+    }
+}
+
 #[cfg(not(no_global_oom_handling))]
 #[stable(feature = "box_from_slice", since = "1.17.0")]
-impl<T: Copy> From<&[T]> for Box<[T]> {
+impl<T: Clone> From<&[T]> for Box<[T]> {
     /// Converts a `&[T]` into a `Box<[T]>`
     ///
     /// This conversion allocates on the heap
@@ -1471,19 +1498,15 @@ impl<T: Copy> From<&[T]> for Box<[T]> {
     ///
     /// println!("{boxed_slice:?}");
     /// ```
+    #[inline]
     fn from(slice: &[T]) -> Box<[T]> {
-        let len = slice.len();
-        let buf = RawVec::with_capacity(len);
-        unsafe {
-            ptr::copy_nonoverlapping(slice.as_ptr(), buf.ptr(), len);
-            buf.into_box(slice.len()).assume_init()
-        }
+        <Self as BoxFromSlice<T>>::from_slice(slice)
     }
 }
 
 #[cfg(not(no_global_oom_handling))]
 #[stable(feature = "box_from_cow", since = "1.45.0")]
-impl<T: Copy> From<Cow<'_, [T]>> for Box<[T]> {
+impl<T: Clone> From<Cow<'_, [T]>> for Box<[T]> {
     /// Converts a `Cow<'_, [T]>` into a `Box<[T]>`
     ///
     /// When `cow` is the `Cow::Borrowed` variant, this

library/core/src/option.rs

@@ -1007,7 +1007,7 @@ impl<T> Option<T> {
     {
         match self {
             Some(x) => x,
-            None => Default::default(),
+            None => T::default(),
         }
     }
 
@@ -1615,11 +1615,7 @@ impl<T> Option<T> {
     where
         T: Default,
     {
-        fn default<T: Default>() -> T {
-            T::default()
-        }
-
-        self.get_or_insert_with(default)
+        self.get_or_insert_with(T::default)
     }
 
     /// Inserts a value computed from `f` into the option if it is [`None`],

library/core/tests/clone.rs

@@ -1,4 +1,5 @@
 #[test]
+#[cfg_attr(not(bootstrap), allow(suspicious_double_ref_op))]
 fn test_borrowed_clone() {
     let x = 5;
     let y: &i32 = &x;

src/bootstrap/config.rs

@@ -1309,7 +1309,7 @@ impl Config {
         if config.llvm_from_ci {
             let triple = &config.build.triple;
             let ci_llvm_bin = config.ci_llvm_root().join("bin");
-            let mut build_target = config
+            let build_target = config
                 .target_config
                 .entry(config.build)
                 .or_insert_with(|| Target::from_triple(&triple));

src/librustdoc/clean/mod.rs

@@ -1529,7 +1529,9 @@ fn maybe_expand_private_type_alias<'tcx>(
     let Res::Def(DefKind::TyAlias, def_id) = path.res else { return None };
     // Substitute private type aliases
     let def_id = def_id.as_local()?;
-    let alias = if !cx.cache.effective_visibilities.is_exported(cx.tcx, def_id.to_def_id()) {
+    let alias = if !cx.cache.effective_visibilities.is_exported(cx.tcx, def_id.to_def_id())
+        && !cx.current_type_aliases.contains_key(&def_id.to_def_id())
+    {
         &cx.tcx.hir().expect_item(def_id).kind
     } else {
         return None;
@@ -1609,7 +1611,7 @@ fn maybe_expand_private_type_alias<'tcx>(
         }
     }
 
-    Some(cx.enter_alias(substs, |cx| clean_ty(ty, cx)))
+    Some(cx.enter_alias(substs, def_id.to_def_id(), |cx| clean_ty(ty, cx)))
 }
 
 pub(crate) fn clean_ty<'tcx>(ty: &hir::Ty<'tcx>, cx: &mut DocContext<'tcx>) -> Type {
@@ -1700,7 +1702,7 @@ fn normalize<'tcx>(
 pub(crate) fn clean_middle_ty<'tcx>(
     bound_ty: ty::Binder<'tcx, Ty<'tcx>>,
     cx: &mut DocContext<'tcx>,
-    def_id: Option<DefId>,
+    parent_def_id: Option<DefId>,
 ) -> Type {
     let bound_ty = normalize(cx, bound_ty).unwrap_or(bound_ty);
     match *bound_ty.skip_binder().kind() {
@@ -1830,7 +1832,9 @@ pub(crate) fn clean_middle_ty<'tcx>(
             Tuple(t.iter().map(|t| clean_middle_ty(bound_ty.rebind(t), cx, None)).collect())
         }
 
-        ty::Alias(ty::Projection, ref data) => clean_projection(bound_ty.rebind(*data), cx, def_id),
+        ty::Alias(ty::Projection, ref data) => {
+            clean_projection(bound_ty.rebind(*data), cx, parent_def_id)
+        }
 
         ty::Param(ref p) => {
             if let Some(bounds) = cx.impl_trait_bounds.remove(&p.index.into()) {
@@ -1841,15 +1845,30 @@ pub(crate) fn clean_middle_ty<'tcx>(
         }
 
         ty::Alias(ty::Opaque, ty::AliasTy { def_id, substs, .. }) => {
-            // Grab the "TraitA + TraitB" from `impl TraitA + TraitB`,
-            // by looking up the bounds associated with the def_id.
-            let bounds = cx
-                .tcx
-                .explicit_item_bounds(def_id)
-                .subst_iter_copied(cx.tcx, substs)
-                .map(|(bound, _)| bound)
-                .collect::<Vec<_>>();
-            clean_middle_opaque_bounds(cx, bounds)
+            // If it's already in the same alias, don't get an infinite loop.
+            if cx.current_type_aliases.contains_key(&def_id) {
+                let path =
+                    external_path(cx, def_id, false, ThinVec::new(), bound_ty.rebind(substs));
+                Type::Path { path }
+            } else {
+                *cx.current_type_aliases.entry(def_id).or_insert(0) += 1;
+                // Grab the "TraitA + TraitB" from `impl TraitA + TraitB`,
+                // by looking up the bounds associated with the def_id.
+                let bounds = cx
+                    .tcx
+                    .explicit_item_bounds(def_id)
+                    .subst_iter_copied(cx.tcx, substs)
+                    .map(|(bound, _)| bound)
+                    .collect::<Vec<_>>();
+                let ty = clean_middle_opaque_bounds(cx, bounds);
+                if let Some(count) = cx.current_type_aliases.get_mut(&def_id) {
+                    *count -= 1;
+                    if *count == 0 {
+                        cx.current_type_aliases.remove(&def_id);
+                    }
+                }
+                ty
+            }
         }
 
         ty::Closure(..) => panic!("Closure"),
@@ -2229,13 +2248,17 @@ fn clean_maybe_renamed_item<'tcx>(
                 generics: clean_generics(ty.generics, cx),
             }),
             ItemKind::TyAlias(hir_ty, generics) => {
+                *cx.current_type_aliases.entry(def_id).or_insert(0) += 1;
                 let rustdoc_ty = clean_ty(hir_ty, cx);
                 let ty = clean_middle_ty(ty::Binder::dummy(hir_ty_to_ty(cx.tcx, hir_ty)), cx, None);
-                TypedefItem(Box::new(Typedef {
-                    type_: rustdoc_ty,
-                    generics: clean_generics(generics, cx),
-                    item_type: Some(ty),
-                }))
+                let generics = clean_generics(generics, cx);
+                if let Some(count) = cx.current_type_aliases.get_mut(&def_id) {
+                    *count -= 1;
+                    if *count == 0 {
+                        cx.current_type_aliases.remove(&def_id);
+                    }
+                }
+                TypedefItem(Box::new(Typedef { type_: rustdoc_ty, generics, item_type: Some(ty) }))
             }
             ItemKind::Enum(ref def, generics) => EnumItem(Enum {
                 variants: def.variants.iter().map(|v| clean_variant(v, cx)).collect(),