Merging upstream version 1.71.1+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 84 insertions, 33 deletions

diff --git a/compiler/rustc_lint/src/noop_method_call.rs b/compiler/rustc_lint/src/noop_method_call.rs
index d67a00619..d56c35bb6 100644
--- a/compiler/rustc_lint/src/noop_method_call.rs
+++ b/compiler/rustc_lint/src/noop_method_call.rs
@@ -1,10 +1,13 @@
 use crate::context::LintContext;
-use crate::lints::NoopMethodCallDiag;
+use crate::lints::{
+    NoopMethodCallDiag, SuspiciousDoubleRefCloneDiag, SuspiciousDoubleRefDerefDiag,
+};
 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! {
@@ -35,32 +38,62 @@ 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) {
-            // Verify we are dealing with a method/associated function.
-            Some((DefKind::AssocFn, did)) => match cx.tcx.trait_of_item(did) {
-                // Check that we're dealing with a trait method for one of the traits we care about.
-                Some(trait_id)
-                    if matches!(
-                        cx.tcx.get_diagnostic_name(trait_id),
-                        Some(sym::Borrow | sym::Clone | sym::Deref)
-                    ) =>
-                {
-                    did
-                }
-                _ => return,
-            },
-            _ => return,
+
+        let Some((DefKind::AssocFn, did)) =
+            cx.typeck_results().type_dependent_def(expr.hir_id)
+        else {
+            return;
         };
+
+        let Some(trait_id) = cx.tcx.trait_of_item(did) else { return };
+
+        if !matches!(
+            cx.tcx.get_diagnostic_name(trait_id),
+            Some(sym::Borrow | sym::Clone | sym::Deref)
+        ) {
+            return;
+        };
+
         let substs = cx
             .tcx
             .normalize_erasing_regions(cx.param_env, cx.typeck_results().node_substs(expr.hir_id));
@@ -70,25 +103,43 @@ 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 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 {
+            match name {
+                // If `type_of(x) == T` and `x.borrow()` is used to get `&T`,
+                // then that should be allowed
+                sym::noop_method_borrow => return,
+                sym::noop_method_clone => cx.emit_spanned_lint(
+                    SUSPICIOUS_DOUBLE_REF_OP,
+                    span,
+                    SuspiciousDoubleRefCloneDiag { ty: expr_ty },
+                ),
+                sym::noop_method_deref => cx.emit_spanned_lint(
+                    SUSPICIOUS_DOUBLE_REF_OP,
+                    span,
+                    SuspiciousDoubleRefDerefDiag { ty: expr_ty },
+                ),
+                _ => return,
+            }
+        }
     }
 }