Auto merge of #10855 - Centri3:explicit_deref_methods, r=llogiq

Fix suggestion on fully qualified syntax

fixes #10850

changelog: [`explicit_deref_methods`]: Fix malformed suggestion on `Foo::deref(&foo)`

4 files changed, 86 insertions, 19 deletions

diff --git a/clippy_lints/src/dereference.rs b/clippy_lints/src/dereference.rs
index a1d2147cb49..7787fc348da 100644
--- a/clippy_lints/src/dereference.rs
+++ b/clippy_lints/src/dereference.rs
@@ -56,9 +56,11 @@ declare_clippy_lint! {
     /// let b = &*a;
     /// ```
     ///
-    /// This lint excludes:
+    /// This lint excludes all of:
     /// ```rust,ignore
     /// let _ = d.unwrap().deref();
+    /// let _ = Foo::deref(&foo);
+    /// let _ = <Foo as Deref>::deref(&foo);
     /// ```
     #[clippy::version = "1.44.0"]
     pub EXPLICIT_DEREF_METHODS,
@@ -1480,7 +1482,7 @@ fn report<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, state: State, data
             target_mut,
         } => {
             let mut app = Applicability::MachineApplicable;
-            let (expr_str, expr_is_macro_call) = snippet_with_context(cx, expr.span, data.span.ctxt(), "..", &mut app);
+            let (expr_str, _expr_is_macro_call) = snippet_with_context(cx, expr.span, data.span.ctxt(), "..", &mut app);
             let ty = cx.typeck_results().expr_ty(expr);
             let (_, ref_count) = peel_mid_ty_refs(ty);
             let deref_str = if ty_changed_count >= ref_count && ref_count != 0 {
@@ -1503,11 +1505,20 @@ fn report<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, state: State, data
                 "&"
             };
 
-            let expr_str = if !expr_is_macro_call && is_final_ufcs && expr.precedence().order() < PREC_PREFIX {
-                format!("({expr_str})")
+            // expr_str (the suggestion) is never shown if is_final_ufcs is true, since it's
+            // `expr.kind == ExprKind::Call`. Therefore, this is, afaik, always unnecessary.
+            /*
+            expr_str = if !expr_is_macro_call && is_final_ufcs && expr.precedence().order() < PREC_PREFIX {
+                Cow::Owned(format!("({expr_str})"))
             } else {
-                expr_str.into_owned()
+                expr_str
             };
+            */
+
+            // Fix #10850, do not lint if it's `Foo::deref` instead of `foo.deref()`.
+            if is_final_ufcs {
+                return;
+            }
 
             span_lint_and_sugg(
                 cx,
diff --git a/tests/ui/explicit_deref_methods.fixed b/tests/ui/explicit_deref_methods.fixed
index 60482c66da7..1710b170fb8 100644
--- a/tests/ui/explicit_deref_methods.fixed
+++ b/tests/ui/explicit_deref_methods.fixed
@@ -1,11 +1,12 @@
 //@run-rustfix
 #![warn(clippy::explicit_deref_methods)]
-#![allow(unused_variables)]
+#![allow(unused_variables, unused_must_use)]
 #![allow(
     clippy::borrow_deref_ref,
     suspicious_double_ref_op,
     clippy::explicit_auto_deref,
     clippy::needless_borrow,
+    clippy::no_effect,
     clippy::uninlined_format_args
 )]
 
@@ -28,6 +29,22 @@ impl Deref for CustomVec {
     }
 }
 
+struct Aaa;
+
+impl Deref for Aaa {
+    type Target = ();
+
+    fn deref(&self) -> &Self::Target {
+        todo!();
+    }
+}
+
+impl DerefMut for Aaa {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        todo!();
+    }
+}
+
 fn main() {
     let a: &mut String = &mut String::from("foo");
 
@@ -58,6 +75,17 @@ fn main() {
     let opt_a = Some(a.clone());
     let b = &*opt_a.unwrap();
 
+    // make sure `Aaa::deref` instead of `aaa.deref()` is not linted, as well as fully qualified
+    // syntax
+
+    Aaa::deref(&Aaa);
+    Aaa::deref_mut(&mut Aaa);
+    <Aaa as Deref>::deref(&Aaa);
+    <Aaa as DerefMut>::deref_mut(&mut Aaa);
+    let mut aaa = Aaa;
+    Aaa::deref(&aaa);
+    Aaa::deref_mut(&mut aaa);
+
     // following should not require linting
 
     let cv = CustomVec(vec![0, 42]);
diff --git a/tests/ui/explicit_deref_methods.rs b/tests/ui/explicit_deref_methods.rs
index e3613e216bb..85147e1cb69 100644
--- a/tests/ui/explicit_deref_methods.rs
+++ b/tests/ui/explicit_deref_methods.rs
@@ -1,11 +1,12 @@
 //@run-rustfix
 #![warn(clippy::explicit_deref_methods)]
-#![allow(unused_variables)]
+#![allow(unused_variables, unused_must_use)]
 #![allow(
     clippy::borrow_deref_ref,
     suspicious_double_ref_op,
     clippy::explicit_auto_deref,
     clippy::needless_borrow,
+    clippy::no_effect,
     clippy::uninlined_format_args
 )]
 
@@ -28,6 +29,22 @@ impl Deref for CustomVec {
     }
 }
 
+struct Aaa;
+
+impl Deref for Aaa {
+    type Target = ();
+
+    fn deref(&self) -> &Self::Target {
+        todo!();
+    }
+}
+
+impl DerefMut for Aaa {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        todo!();
+    }
+}
+
 fn main() {
     let a: &mut String = &mut String::from("foo");
 
@@ -58,6 +75,17 @@ fn main() {
     let opt_a = Some(a.clone());
     let b = opt_a.unwrap().deref();
 
+    // make sure `Aaa::deref` instead of `aaa.deref()` is not linted, as well as fully qualified
+    // syntax
+
+    Aaa::deref(&Aaa);
+    Aaa::deref_mut(&mut Aaa);
+    <Aaa as Deref>::deref(&Aaa);
+    <Aaa as DerefMut>::deref_mut(&mut Aaa);
+    let mut aaa = Aaa;
+    Aaa::deref(&aaa);
+    Aaa::deref_mut(&mut aaa);
+
     // following should not require linting
 
     let cv = CustomVec(vec![0, 42]);
diff --git a/tests/ui/explicit_deref_methods.stderr b/tests/ui/explicit_deref_methods.stderr
index 4b10ed1377b..592563ffa8c 100644
--- a/tests/ui/explicit_deref_methods.stderr
+++ b/tests/ui/explicit_deref_methods.stderr
@@ -1,5 +1,5 @@
 error: explicit `deref` method call
-  --> $DIR/explicit_deref_methods.rs:36:19
+  --> $DIR/explicit_deref_methods.rs:53:19
    |
 LL |     let b: &str = a.deref();
    |                   ^^^^^^^^^ help: try this: `&*a`
@@ -7,67 +7,67 @@ LL |     let b: &str = a.deref();
    = note: `-D clippy::explicit-deref-methods` implied by `-D warnings`
 
 error: explicit `deref_mut` method call
-  --> $DIR/explicit_deref_methods.rs:38:23
+  --> $DIR/explicit_deref_methods.rs:55:23
    |
 LL |     let b: &mut str = a.deref_mut();
    |                       ^^^^^^^^^^^^^ help: try this: `&mut **a`
 
 error: explicit `deref` method call
-  --> $DIR/explicit_deref_methods.rs:41:39
+  --> $DIR/explicit_deref_methods.rs:58:39
    |
 LL |     let b: String = format!("{}, {}", a.deref(), a.deref());
    |                                       ^^^^^^^^^ help: try this: `&*a`
 
 error: explicit `deref` method call
-  --> $DIR/explicit_deref_methods.rs:41:50
+  --> $DIR/explicit_deref_methods.rs:58:50
    |
 LL |     let b: String = format!("{}, {}", a.deref(), a.deref());
    |                                                  ^^^^^^^^^ help: try this: `&*a`
 
 error: explicit `deref` method call
-  --> $DIR/explicit_deref_methods.rs:43:20
+  --> $DIR/explicit_deref_methods.rs:60:20
    |
 LL |     println!("{}", a.deref());
    |                    ^^^^^^^^^ help: try this: `&*a`
 
 error: explicit `deref` method call
-  --> $DIR/explicit_deref_methods.rs:46:11
+  --> $DIR/explicit_deref_methods.rs:63:11
    |
 LL |     match a.deref() {
    |           ^^^^^^^^^ help: try this: `&*a`
 
 error: explicit `deref` method call
-  --> $DIR/explicit_deref_methods.rs:50:28
+  --> $DIR/explicit_deref_methods.rs:67:28
    |
 LL |     let b: String = concat(a.deref());
    |                            ^^^^^^^^^ help: try this: `&*a`
 
 error: explicit `deref` method call
-  --> $DIR/explicit_deref_methods.rs:52:13
+  --> $DIR/explicit_deref_methods.rs:69:13
    |
 LL |     let b = just_return(a).deref();
    |             ^^^^^^^^^^^^^^^^^^^^^^ help: try this: `just_return(a)`
 
 error: explicit `deref` method call
-  --> $DIR/explicit_deref_methods.rs:54:28
+  --> $DIR/explicit_deref_methods.rs:71:28
    |
 LL |     let b: String = concat(just_return(a).deref());
    |                            ^^^^^^^^^^^^^^^^^^^^^^ help: try this: `just_return(a)`
 
 error: explicit `deref` method call
-  --> $DIR/explicit_deref_methods.rs:56:19
+  --> $DIR/explicit_deref_methods.rs:73:19
    |
 LL |     let b: &str = a.deref().deref();
    |                   ^^^^^^^^^^^^^^^^^ help: try this: `&**a`
 
 error: explicit `deref` method call
-  --> $DIR/explicit_deref_methods.rs:59:13
+  --> $DIR/explicit_deref_methods.rs:76:13
    |
 LL |     let b = opt_a.unwrap().deref();
    |             ^^^^^^^^^^^^^^^^^^^^^^ help: try this: `&*opt_a.unwrap()`
 
 error: explicit `deref` method call
-  --> $DIR/explicit_deref_methods.rs:85:31
+  --> $DIR/explicit_deref_methods.rs:113:31
    |
 LL |     let b: &str = expr_deref!(a.deref());
    |                               ^^^^^^^^^ help: try this: `&*a`