add suggestion

compiler/rustc_lint/messages.ftl

@@ -412,7 +412,7 @@ lint_non_upper_case_global = {$sort} `{$name}` should have an upper case name
     .label = should have an UPPER_CASE name
 
 lint_noop_method_call = call to `.{$method}()` on a reference in this situation does nothing
-    .label = unnecessary method call
+    .suggestion = remove this redundant call
     .note = the type `{$orig_ty}` does not implement `{$trait_}`, so calling `{$method}` on `&{$orig_ty}` copies the reference, which does not do anything and can be removed
 
 lint_only_cast_u8_to_char = only `u8` can be cast into `char`

compiler/rustc_lint/src/lints.rs

@@ -1233,7 +1233,7 @@ pub struct NoopMethodCallDiag<'a> {
     pub method: Symbol,
     pub orig_ty: Ty<'a>,
     pub trait_: Symbol,
-    #[label]
+    #[suggestion(code = "", applicability = "machine-applicable")]
     pub label: Span,
 }
 

tests/ui/lint/noop-method-call.fixed

@@ -0,0 +1,51 @@
+// check-pass
+// run-rustfix
+
+#![allow(unused)]
+
+use std::borrow::Borrow;
+use std::ops::Deref;
+
+struct PlainType<T>(T);
+
+#[derive(Clone)]
+struct CloneType<T>(T);
+
+fn check(mut encoded: &[u8]) {
+    let _ = &mut encoded;
+    //~^ WARN call to `.clone()` on a reference in this situation does nothing
+    let _ = &encoded;
+    //~^ WARN call to `.clone()` on a reference in this situation does nothing
+}
+
+fn main() {
+    let non_clone_type_ref = &PlainType(1u32);
+    let non_clone_type_ref_clone: &PlainType<u32> = non_clone_type_ref;
+    //~^ WARN call to `.clone()` on a reference in this situation does nothing
+
+    let clone_type_ref = &CloneType(1u32);
+    let clone_type_ref_clone: CloneType<u32> = clone_type_ref.clone();
+
+
+    let non_deref_type = &PlainType(1u32);
+    let non_deref_type_deref: &PlainType<u32> = non_deref_type;
+    //~^ WARN call to `.deref()` on a reference in this situation does nothing
+
+    let non_borrow_type = &PlainType(1u32);
+    let non_borrow_type_borrow: &PlainType<u32> = non_borrow_type;
+    //~^ WARN call to `.borrow()` on a reference in this situation does nothing
+
+    // Borrowing a &&T does not warn since it has collapsed the double reference
+    let non_borrow_type = &&PlainType(1u32);
+    let non_borrow_type_borrow: &PlainType<u32> = non_borrow_type.borrow();
+}
+
+fn generic<T>(non_clone_type: &PlainType<T>) {
+    non_clone_type;
+    //~^ WARN call to `.clone()` on a reference in this situation does nothing
+}
+
+fn non_generic(non_clone_type: &PlainType<u32>) {
+    non_clone_type;
+    //~^ WARN call to `.clone()` on a reference in this situation does nothing
+}

tests/ui/lint/noop-method-call.rs

@@ -1,4 +1,5 @@
 // check-pass
+// run-rustfix
 
 #![allow(unused)]
 
@@ -10,45 +11,41 @@ struct PlainType<T>(T);
 #[derive(Clone)]
 struct CloneType<T>(T);
 
+fn check(mut encoded: &[u8]) {
+    let _ = &mut encoded.clone();
+    //~^ WARN call to `.clone()` on a reference in this situation does nothing
+    let _ = &encoded.clone();
+    //~^ WARN call to `.clone()` on a reference in this situation does nothing
+}
+
 fn main() {
     let non_clone_type_ref = &PlainType(1u32);
     let non_clone_type_ref_clone: &PlainType<u32> = non_clone_type_ref.clone();
-    //~^ WARNING call to `.clone()` on a reference in this situation does nothing
+    //~^ WARN call to `.clone()` on a reference in this situation does nothing
 
     let clone_type_ref = &CloneType(1u32);
     let clone_type_ref_clone: CloneType<u32> = clone_type_ref.clone();
 
-    let clone_type_ref = &&CloneType(1u32);
-    let clone_type_ref_clone: &CloneType<u32> = clone_type_ref.clone();
-    //~^ WARNING using `.clone()` on a double reference, which returns `&CloneType<u32>`
 
     let non_deref_type = &PlainType(1u32);
     let non_deref_type_deref: &PlainType<u32> = non_deref_type.deref();
-    //~^ WARNING call to `.deref()` on a reference in this situation does nothing
-
-    let non_deref_type = &&PlainType(1u32);
-    let non_deref_type_deref: &PlainType<u32> = non_deref_type.deref();
-    //~^ WARNING using `.deref()` on a double reference, which returns `&PlainType<u32>`
+    //~^ WARN call to `.deref()` on a reference in this situation does nothing
 
     let non_borrow_type = &PlainType(1u32);
     let non_borrow_type_borrow: &PlainType<u32> = non_borrow_type.borrow();
-    //~^ WARNING call to `.borrow()` on a reference in this situation does nothing
+    //~^ WARN call to `.borrow()` on a reference in this situation does nothing
 
     // Borrowing a &&T does not warn since it has collapsed the double reference
     let non_borrow_type = &&PlainType(1u32);
     let non_borrow_type_borrow: &PlainType<u32> = non_borrow_type.borrow();
-
-    let xs = ["a", "b", "c"];
-    let _v: Vec<&str> = xs.iter().map(|x| x.clone()).collect(); // could use `*x` instead
-    //~^ WARNING using `.clone()` on a double reference, which returns `&str`
 }
 
 fn generic<T>(non_clone_type: &PlainType<T>) {
     non_clone_type.clone();
-    //~^ WARNING call to `.clone()` on a reference in this situation does nothing
+    //~^ WARN call to `.clone()` on a reference in this situation does nothing
 }
 
 fn non_generic(non_clone_type: &PlainType<u32>) {
     non_clone_type.clone();
-    //~^ WARNING call to `.clone()` on a reference in this situation does nothing
+    //~^ WARN call to `.clone()` on a reference in this situation does nothing
 }

tests/ui/lint/noop-method-call.stderr

@@ -1,63 +1,59 @@
 warning: call to `.clone()` on a reference in this situation does nothing
-  --> $DIR/noop-method-call.rs:15:71
+  --> $DIR/noop-method-call.rs:15:25
    |
-LL |     let non_clone_type_ref_clone: &PlainType<u32> = non_clone_type_ref.clone();
-   |                                                                       ^^^^^^^^ unnecessary method call
+LL |     let _ = &mut encoded.clone();
+   |                         ^^^^^^^^ help: remove this redundant call
    |
-   = note: the type `PlainType<u32>` does not implement `Clone`, so calling `clone` on `&PlainType<u32>` copies the reference, which does not do anything and can be removed
+   = note: the type `[u8]` does not implement `Clone`, so calling `clone` on `&[u8]` copies the reference, which does not do anything and can be removed
    = note: `#[warn(noop_method_call)]` on by default
 
-warning: using `.clone()` on a double reference, which returns `&CloneType<u32>` instead of cloning the inner type
-  --> $DIR/noop-method-call.rs:22:63
+warning: call to `.clone()` on a reference in this situation does nothing
+  --> $DIR/noop-method-call.rs:17:21
    |
-LL |     let clone_type_ref_clone: &CloneType<u32> = clone_type_ref.clone();
-   |                                                               ^^^^^^^^
+LL |     let _ = &encoded.clone();
+   |                     ^^^^^^^^ help: remove this redundant call
    |
-   = note: `#[warn(suspicious_double_ref_op)]` on by default
+   = note: the type `[u8]` does not implement `Clone`, so calling `clone` on `&[u8]` copies the reference, which does not do anything and can be removed
 
-warning: call to `.deref()` on a reference in this situation does nothing
-  --> $DIR/noop-method-call.rs:26:63
+warning: call to `.clone()` on a reference in this situation does nothing
+  --> $DIR/noop-method-call.rs:23:71
    |
-LL |     let non_deref_type_deref: &PlainType<u32> = non_deref_type.deref();
-   |                                                               ^^^^^^^^ unnecessary method call
+LL |     let non_clone_type_ref_clone: &PlainType<u32> = non_clone_type_ref.clone();
+   |                                                                       ^^^^^^^^ help: remove this redundant call
    |
-   = note: the type `PlainType<u32>` does not implement `Deref`, so calling `deref` on `&PlainType<u32>` copies the reference, which does not do anything and can be removed
+   = note: the type `PlainType<u32>` does not implement `Clone`, so calling `clone` on `&PlainType<u32>` copies the reference, which does not do anything and can be removed
 
-warning: using `.deref()` on a double reference, which returns `&PlainType<u32>` instead of dereferencing the inner type
-  --> $DIR/noop-method-call.rs:30:63
+warning: call to `.deref()` on a reference in this situation does nothing
+  --> $DIR/noop-method-call.rs:31:63
    |
 LL |     let non_deref_type_deref: &PlainType<u32> = non_deref_type.deref();
-   |                                                               ^^^^^^^^
+   |                                                               ^^^^^^^^ help: remove this redundant call
+   |
+   = note: the type `PlainType<u32>` does not implement `Deref`, so calling `deref` on `&PlainType<u32>` copies the reference, which does not do anything and can be removed
 
 warning: call to `.borrow()` on a reference in this situation does nothing
-  --> $DIR/noop-method-call.rs:34:66
+  --> $DIR/noop-method-call.rs:35:66
    |
 LL |     let non_borrow_type_borrow: &PlainType<u32> = non_borrow_type.borrow();
-   |                                                                  ^^^^^^^^^ unnecessary method call
+   |                                                                  ^^^^^^^^^ help: remove this redundant call
    |
    = note: the type `PlainType<u32>` does not implement `Borrow`, so calling `borrow` on `&PlainType<u32>` copies the reference, which does not do anything and can be removed
 
-warning: using `.clone()` on a double reference, which returns `&str` instead of cloning the inner type
-  --> $DIR/noop-method-call.rs:42:44
-   |
-LL |     let _v: Vec<&str> = xs.iter().map(|x| x.clone()).collect(); // could use `*x` instead
-   |                                            ^^^^^^^^
-
 warning: call to `.clone()` on a reference in this situation does nothing
-  --> $DIR/noop-method-call.rs:47:19
+  --> $DIR/noop-method-call.rs:44:19
    |
 LL |     non_clone_type.clone();
-   |                   ^^^^^^^^ unnecessary method call
+   |                   ^^^^^^^^ help: remove this redundant call
    |
    = note: the type `PlainType<T>` does not implement `Clone`, so calling `clone` on `&PlainType<T>` copies the reference, which does not do anything and can be removed
 
 warning: call to `.clone()` on a reference in this situation does nothing
-  --> $DIR/noop-method-call.rs:52:19
+  --> $DIR/noop-method-call.rs:49:19
    |
 LL |     non_clone_type.clone();
-   |                   ^^^^^^^^ unnecessary method call
+   |                   ^^^^^^^^ help: remove this redundant call
    |
    = note: the type `PlainType<u32>` does not implement `Clone`, so calling `clone` on `&PlainType<u32>` copies the reference, which does not do anything and can be removed
 
-warning: 8 warnings emitted
+warning: 7 warnings emitted
 

tests/ui/lint/suspicious-double-ref-op.rs

@@ -1,6 +1,14 @@
 #![feature(lazy_cell)]
 #![deny(suspicious_double_ref_op, noop_method_call)]
 
+use std::borrow::Borrow;
+use std::ops::Deref;
+
+struct PlainType<T>(T);
+
+#[derive(Clone)]
+struct CloneType<T>(T);
+
 pub fn clone_on_double_ref() {
     let x = vec![1];
     let y = &&x;
@@ -20,11 +28,16 @@ fn rust_clippy_issue_9272() {
     println!("{str}")
 }
 
-fn check(mut encoded: &[u8]) {
-    let _ = &mut encoded.clone();
-    //~^ ERROR call to `.clone()` on a reference in this situation does nothing
-    let _ = &encoded.clone();
-    //~^ ERROR call to `.clone()` on a reference in this situation does nothing
-}
+fn main() {
+    let clone_type_ref = &&CloneType(1u32);
+    let clone_type_ref_clone: &CloneType<u32> = clone_type_ref.clone();
+    //~^ ERROR using `.clone()` on a double reference, which returns `&CloneType<u32>`
+
+    let non_deref_type = &&PlainType(1u32);
+    let non_deref_type_deref: &PlainType<u32> = non_deref_type.deref();
+    //~^ ERROR using `.deref()` on a double reference, which returns `&PlainType<u32>`
 
-fn main() {}
+    let xs = ["a", "b", "c"];
+    let _v: Vec<&str> = xs.iter().map(|x| x.clone()).collect(); // could use `*x` instead
+    //~^ ERROR using `.clone()` on a double reference, which returns `&str`
+}

tests/ui/lint/suspicious-double-ref-op.stderr

@@ -1,5 +1,5 @@
 error: using `.clone()` on a double reference, which returns `&Vec<i32>` instead of cloning the inner type
-  --> $DIR/suspicious-double-ref-op.rs:7:23
+  --> $DIR/suspicious-double-ref-op.rs:15:23
    |
 LL |     let z: &Vec<_> = y.clone();
    |                       ^^^^^^^^
@@ -10,26 +10,23 @@ note: the lint level is defined here
 LL | #![deny(suspicious_double_ref_op, noop_method_call)]
    |         ^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: call to `.clone()` on a reference in this situation does nothing
-  --> $DIR/suspicious-double-ref-op.rs:24:25
+error: using `.clone()` on a double reference, which returns `&CloneType<u32>` instead of cloning the inner type
+  --> $DIR/suspicious-double-ref-op.rs:33:63
    |
-LL |     let _ = &mut encoded.clone();
-   |                         ^^^^^^^^ unnecessary method call
-   |
-   = note: the type `[u8]` does not implement `Clone`, so calling `clone` on `&[u8]` copies the reference, which does not do anything and can be removed
-note: the lint level is defined here
-  --> $DIR/suspicious-double-ref-op.rs:2:35
-   |
-LL | #![deny(suspicious_double_ref_op, noop_method_call)]
-   |                                   ^^^^^^^^^^^^^^^^
+LL |     let clone_type_ref_clone: &CloneType<u32> = clone_type_ref.clone();
+   |                                                               ^^^^^^^^
 
-error: call to `.clone()` on a reference in this situation does nothing
-  --> $DIR/suspicious-double-ref-op.rs:26:21
+error: using `.deref()` on a double reference, which returns `&PlainType<u32>` instead of dereferencing the inner type
+  --> $DIR/suspicious-double-ref-op.rs:37:63
    |
-LL |     let _ = &encoded.clone();
-   |                     ^^^^^^^^ unnecessary method call
+LL |     let non_deref_type_deref: &PlainType<u32> = non_deref_type.deref();
+   |                                                               ^^^^^^^^
+
+error: using `.clone()` on a double reference, which returns `&str` instead of cloning the inner type
+  --> $DIR/suspicious-double-ref-op.rs:41:44
    |
-   = note: the type `[u8]` does not implement `Clone`, so calling `clone` on `&[u8]` copies the reference, which does not do anything and can be removed
+LL |     let _v: Vec<&str> = xs.iter().map(|x| x.clone()).collect(); // could use `*x` instead
+   |                                            ^^^^^^^^
 
-error: aborting due to 3 previous errors
+error: aborting due to 4 previous errors