Fix coerce_container_to_any false positive on autoderef (#15057)
Fixes the false positive reported in rust-lang/rust-clippy#15045. ~I
still need to work out how to fix the suggestion.~
changelog: none
diff --git a/clippy_lints/src/coerce_container_to_any.rs b/clippy_lints/src/coerce_container_to_any.rs
index 2b65925..6217fc4 100644
--- a/clippy_lints/src/coerce_container_to_any.rs
+++ b/clippy_lints/src/coerce_container_to_any.rs
@@ -1,9 +1,10 @@
use clippy_utils::diagnostics::span_lint_and_sugg;
-use clippy_utils::source::snippet;
+use clippy_utils::sugg::{self, Sugg};
use clippy_utils::sym;
use rustc_errors::Applicability;
use rustc_hir::{Expr, ExprKind};
use rustc_lint::{LateContext, LateLintPass};
+use rustc_middle::ty::adjustment::{Adjust, PointerCoercion};
use rustc_middle::ty::{self, ExistentialPredicate, Ty, TyCtxt};
use rustc_session::declare_lint_pass;
@@ -49,23 +50,18 @@
impl<'tcx> LateLintPass<'tcx> for CoerceContainerToAny {
fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) {
- // If this expression has an effective type of `&dyn Any` ...
- {
- let coerced_ty = cx.typeck_results().expr_ty_adjusted(e);
-
- let ty::Ref(_, coerced_ref_ty, _) = *coerced_ty.kind() else {
- return;
- };
- if !is_dyn_any(cx.tcx, coerced_ref_ty) {
- return;
- }
+ // If this expression was coerced to `&dyn Any` ...
+ if !cx.typeck_results().expr_adjustments(e).last().is_some_and(|adj| {
+ matches!(adj.kind, Adjust::Pointer(PointerCoercion::Unsize)) && is_ref_dyn_any(cx.tcx, adj.target)
+ }) {
+ return;
}
let expr_ty = cx.typeck_results().expr_ty(e);
let ty::Ref(_, expr_ref_ty, _) = *expr_ty.kind() else {
return;
};
- // ... but only due to coercion ...
+ // ... but it's not actually `&dyn Any` ...
if is_dyn_any(cx.tcx, expr_ref_ty) {
return;
}
@@ -78,23 +74,37 @@
}
// ... that's probably not intended.
- let (span, deref_count) = match e.kind {
+ let (target_expr, deref_count) = match e.kind {
// If `e` was already an `&` expression, skip `*&` in the suggestion
- ExprKind::AddrOf(_, _, referent) => (referent.span, depth),
- _ => (e.span, depth + 1),
+ ExprKind::AddrOf(_, _, referent) => (referent, depth),
+ _ => (e, depth + 1),
};
+ let ty::Ref(_, _, mutability) = *cx.typeck_results().expr_ty_adjusted(e).kind() else {
+ return;
+ };
+ let sugg = sugg::make_unop(
+ &format!("{}{}", mutability.ref_prefix_str(), str::repeat("*", deref_count)),
+ Sugg::hir(cx, target_expr, ".."),
+ );
span_lint_and_sugg(
cx,
COERCE_CONTAINER_TO_ANY,
e.span,
- format!("coercing `{expr_ty}` to `&dyn Any`"),
+ format!("coercing `{expr_ty}` to `{}dyn Any`", mutability.ref_prefix_str()),
"consider dereferencing",
- format!("&{}{}", str::repeat("*", deref_count), snippet(cx, span, "x")),
+ sugg.to_string(),
Applicability::MaybeIncorrect,
);
}
}
+fn is_ref_dyn_any(tcx: TyCtxt<'_>, ty: Ty<'_>) -> bool {
+ let ty::Ref(_, ref_ty, _) = *ty.kind() else {
+ return false;
+ };
+ is_dyn_any(tcx, ref_ty)
+}
+
fn is_dyn_any(tcx: TyCtxt<'_>, ty: Ty<'_>) -> bool {
let ty::Dynamic(traits, ..) = ty.kind() else {
return false;
diff --git a/tests/ui/coerce_container_to_any.fixed b/tests/ui/coerce_container_to_any.fixed
index ae9d3ef..b5b3f15 100644
--- a/tests/ui/coerce_container_to_any.fixed
+++ b/tests/ui/coerce_container_to_any.fixed
@@ -3,7 +3,7 @@
use std::any::Any;
fn main() {
- let x: Box<dyn Any> = Box::new(());
+ let mut x: Box<dyn Any> = Box::new(());
let ref_x = &x;
f(&*x);
@@ -15,12 +15,23 @@
let _: &dyn Any = &*x;
//~^ coerce_container_to_any
+ let _: &dyn Any = &*x;
+ //~^ coerce_container_to_any
+
+ let _: &mut dyn Any = &mut *x;
+ //~^ coerce_container_to_any
+
f(&42);
f(&Box::new(()));
f(&Box::new(Box::new(())));
+ let ref_x = &x;
f(&**ref_x);
f(&*x);
let _: &dyn Any = &*x;
+
+ // https://github.com/rust-lang/rust-clippy/issues/15045
+ #[allow(clippy::needless_borrow)]
+ (&x).downcast_ref::<()>().unwrap();
}
fn f(_: &dyn Any) {}
diff --git a/tests/ui/coerce_container_to_any.rs b/tests/ui/coerce_container_to_any.rs
index 9948bd4..4d6527b 100644
--- a/tests/ui/coerce_container_to_any.rs
+++ b/tests/ui/coerce_container_to_any.rs
@@ -3,7 +3,7 @@
use std::any::Any;
fn main() {
- let x: Box<dyn Any> = Box::new(());
+ let mut x: Box<dyn Any> = Box::new(());
let ref_x = &x;
f(&x);
@@ -15,12 +15,23 @@
let _: &dyn Any = &x;
//~^ coerce_container_to_any
+ let _: &dyn Any = &mut x;
+ //~^ coerce_container_to_any
+
+ let _: &mut dyn Any = &mut x;
+ //~^ coerce_container_to_any
+
f(&42);
f(&Box::new(()));
f(&Box::new(Box::new(())));
+ let ref_x = &x;
f(&**ref_x);
f(&*x);
let _: &dyn Any = &*x;
+
+ // https://github.com/rust-lang/rust-clippy/issues/15045
+ #[allow(clippy::needless_borrow)]
+ (&x).downcast_ref::<()>().unwrap();
}
fn f(_: &dyn Any) {}
diff --git a/tests/ui/coerce_container_to_any.stderr b/tests/ui/coerce_container_to_any.stderr
index 00ab77e..26389c9 100644
--- a/tests/ui/coerce_container_to_any.stderr
+++ b/tests/ui/coerce_container_to_any.stderr
@@ -19,5 +19,17 @@
LL | let _: &dyn Any = &x;
| ^^ help: consider dereferencing: `&*x`
-error: aborting due to 3 previous errors
+error: coercing `&mut std::boxed::Box<dyn std::any::Any>` to `&dyn Any`
+ --> tests/ui/coerce_container_to_any.rs:18:23
+ |
+LL | let _: &dyn Any = &mut x;
+ | ^^^^^^ help: consider dereferencing: `&*x`
+
+error: coercing `&mut std::boxed::Box<dyn std::any::Any>` to `&mut dyn Any`
+ --> tests/ui/coerce_container_to_any.rs:21:27
+ |
+LL | let _: &mut dyn Any = &mut x;
+ | ^^^^^^ help: consider dereferencing: `&mut *x`
+
+error: aborting due to 5 previous errors
