Let lint_forgetting_references give the suggestion if possible

7 files changed, 345 insertions, 20 deletions

diff --git a/tests/ui/lint/dropping_copy_types.stderr b/tests/ui/lint/dropping_copy_types.stderr
index bdeb0c290fe..41aa66a4efc 100644
--- a/tests/ui/lint/dropping_copy_types.stderr
+++ b/tests/ui/lint/dropping_copy_types.stderr
@@ -39,8 +39,12 @@ LL |     drop(s3);
    |          |
    |          argument has type `&SomeStruct`
    |
-   = note: use `let _ = ...` to ignore the expression or result
    = note: `#[warn(dropping_references)]` on by default
+help: use `let _ = ...` to ignore the expression or result
+   |
+LL -     drop(s3);
+LL +     let _ = s3;
+   |
 
 warning: calls to `std::mem::drop` with a value that implements `Copy` does nothing
   --> $DIR/dropping_copy_types.rs:37:5
@@ -64,7 +68,11 @@ LL |     drop(s5);
    |          |
    |          argument has type `&SomeStruct`
    |
-   = note: use `let _ = ...` to ignore the expression or result
+help: use `let _ = ...` to ignore the expression or result
+   |
+LL -     drop(s5);
+LL +     let _ = s5;
+   |
 
 warning: calls to `std::mem::drop` with a reference instead of an owned value does nothing
   --> $DIR/dropping_copy_types.rs:50:5
@@ -74,7 +82,11 @@ LL |     drop(a2);
    |          |
    |          argument has type `&AnotherStruct`
    |
-   = note: use `let _ = ...` to ignore the expression or result
+help: use `let _ = ...` to ignore the expression or result
+   |
+LL -     drop(a2);
+LL +     let _ = a2;
+   |
 
 warning: calls to `std::mem::drop` with a reference instead of an owned value does nothing
   --> $DIR/dropping_copy_types.rs:52:5
@@ -84,7 +96,11 @@ LL |     drop(a4);
    |          |
    |          argument has type `&AnotherStruct`
    |
-   = note: use `let _ = ...` to ignore the expression or result
+help: use `let _ = ...` to ignore the expression or result
+   |
+LL -     drop(a4);
+LL +     let _ = a4;
+   |
 
 warning: calls to `std::mem::drop` with a value that implements `Copy` does nothing
   --> $DIR/dropping_copy_types.rs:71:13
diff --git a/tests/ui/lint/forgetting_copy_types.stderr b/tests/ui/lint/forgetting_copy_types.stderr
index a2b07351d79..980ee6caba2 100644
--- a/tests/ui/lint/forgetting_copy_types.stderr
+++ b/tests/ui/lint/forgetting_copy_types.stderr
@@ -39,8 +39,12 @@ LL |     forget(s3);
    |            |
    |            argument has type `&SomeStruct`
    |
-   = note: use `let _ = ...` to ignore the expression or result
    = note: `#[warn(forgetting_references)]` on by default
+help: use `let _ = ...` to ignore the expression or result
+   |
+LL -     forget(s3);
+LL +     let _ = s3;
+   |
 
 warning: calls to `std::mem::forget` with a value that implements `Copy` does nothing
   --> $DIR/forgetting_copy_types.rs:37:5
@@ -64,7 +68,11 @@ LL |     forget(s5);
    |            |
    |            argument has type `&SomeStruct`
    |
-   = note: use `let _ = ...` to ignore the expression or result
+help: use `let _ = ...` to ignore the expression or result
+   |
+LL -     forget(s5);
+LL +     let _ = s5;
+   |
 
 warning: calls to `std::mem::forget` with a reference instead of an owned value does nothing
   --> $DIR/forgetting_copy_types.rs:50:5
@@ -74,7 +82,11 @@ LL |     forget(a2);
    |            |
    |            argument has type `&AnotherStruct`
    |
-   = note: use `let _ = ...` to ignore the expression or result
+help: use `let _ = ...` to ignore the expression or result
+   |
+LL -     forget(a2);
+LL +     let _ = a2;
+   |
 
 warning: calls to `std::mem::forget` with a reference instead of an owned value does nothing
   --> $DIR/forgetting_copy_types.rs:52:5
@@ -84,7 +96,11 @@ LL |     forget(a3);
    |            |
    |            argument has type `&AnotherStruct`
    |
-   = note: use `let _ = ...` to ignore the expression or result
+help: use `let _ = ...` to ignore the expression or result
+   |
+LL -     forget(a3);
+LL +     let _ = a3;
+   |
 
 warning: calls to `std::mem::forget` with a reference instead of an owned value does nothing
   --> $DIR/forgetting_copy_types.rs:53:5
@@ -94,7 +110,11 @@ LL |     forget(a4);
    |            |
    |            argument has type `&AnotherStruct`
    |
-   = note: use `let _ = ...` to ignore the expression or result
+help: use `let _ = ...` to ignore the expression or result
+   |
+LL -     forget(a4);
+LL +     let _ = a4;
+   |
 
 warning: 8 warnings emitted
 
diff --git a/tests/ui/lint/forgetting_references-can-fixed.fixed b/tests/ui/lint/forgetting_references-can-fixed.fixed
new file mode 100644
index 00000000000..64475f04284
--- /dev/null
+++ b/tests/ui/lint/forgetting_references-can-fixed.fixed
@@ -0,0 +1,40 @@
+//@ check-fail
+//@ run-rustfix
+
+#![deny(forgetting_references)]
+
+use std::mem::forget;
+
+struct SomeStruct;
+
+fn main() {
+    let _ = &SomeStruct; //~ ERROR calls to `std::mem::forget`
+
+    let mut owned = SomeStruct;
+    let _ = &owned; //~ ERROR calls to `std::mem::forget`
+    let _ = &&owned; //~ ERROR calls to `std::mem::forget`
+    let _ = &mut owned; //~ ERROR calls to `std::mem::forget`
+    forget(owned);
+
+    let reference1 = &SomeStruct;
+    let _ = &*reference1; //~ ERROR calls to `std::mem::forget`
+
+    let reference2 = &mut SomeStruct;
+    let _ = reference2; //~ ERROR calls to `std::mem::forget`
+
+    let ref reference3 = SomeStruct;
+    let _ = reference3; //~ ERROR calls to `std::mem::forget`
+}
+
+#[allow(dead_code)]
+fn test_generic_fn_forget<T>(val: T) {
+    let _ = &val; //~ ERROR calls to `std::mem::forget`
+    forget(val);
+}
+
+#[allow(dead_code)]
+fn test_similarly_named_function() {
+    fn forget<T>(_val: T) {}
+    forget(&SomeStruct); //OK; call to unrelated function which happens to have the same name
+    let _ = &SomeStruct; //~ ERROR calls to `std::mem::forget`
+}
diff --git a/tests/ui/lint/forgetting_references-can-fixed.rs b/tests/ui/lint/forgetting_references-can-fixed.rs
new file mode 100644
index 00000000000..4c9ef541d34
--- /dev/null
+++ b/tests/ui/lint/forgetting_references-can-fixed.rs
@@ -0,0 +1,40 @@
+//@ check-fail
+//@ run-rustfix
+
+#![deny(forgetting_references)]
+
+use std::mem::forget;
+
+struct SomeStruct;
+
+fn main() {
+    forget(&SomeStruct); //~ ERROR calls to `std::mem::forget`
+
+    let mut owned = SomeStruct;
+    forget(&owned); //~ ERROR calls to `std::mem::forget`
+    forget(&&owned); //~ ERROR calls to `std::mem::forget`
+    forget(&mut owned); //~ ERROR calls to `std::mem::forget`
+    forget(owned);
+
+    let reference1 = &SomeStruct;
+    forget(&*reference1); //~ ERROR calls to `std::mem::forget`
+
+    let reference2 = &mut SomeStruct;
+    forget(reference2); //~ ERROR calls to `std::mem::forget`
+
+    let ref reference3 = SomeStruct;
+    forget(reference3); //~ ERROR calls to `std::mem::forget`
+}
+
+#[allow(dead_code)]
+fn test_generic_fn_forget<T>(val: T) {
+    forget(&val); //~ ERROR calls to `std::mem::forget`
+    forget(val);
+}
+
+#[allow(dead_code)]
+fn test_similarly_named_function() {
+    fn forget<T>(_val: T) {}
+    forget(&SomeStruct); //OK; call to unrelated function which happens to have the same name
+    std::mem::forget(&SomeStruct); //~ ERROR calls to `std::mem::forget`
+}
diff --git a/tests/ui/lint/forgetting_references-can-fixed.stderr b/tests/ui/lint/forgetting_references-can-fixed.stderr
new file mode 100644
index 00000000000..05eb636ab45
--- /dev/null
+++ b/tests/ui/lint/forgetting_references-can-fixed.stderr
@@ -0,0 +1,133 @@
+error: calls to `std::mem::forget` with a reference instead of an owned value does nothing
+  --> $DIR/forgetting_references-can-fixed.rs:11:5
+   |
+LL |     forget(&SomeStruct);
+   |     ^^^^^^^-----------^
+   |            |
+   |            argument has type `&SomeStruct`
+   |
+note: the lint level is defined here
+  --> $DIR/forgetting_references-can-fixed.rs:4:9
+   |
+LL | #![deny(forgetting_references)]
+   |         ^^^^^^^^^^^^^^^^^^^^^
+help: use `let _ = ...` to ignore the expression or result
+   |
+LL -     forget(&SomeStruct);
+LL +     let _ = &SomeStruct;
+   |
+
+error: calls to `std::mem::forget` with a reference instead of an owned value does nothing
+  --> $DIR/forgetting_references-can-fixed.rs:14:5
+   |
+LL |     forget(&owned);
+   |     ^^^^^^^------^
+   |            |
+   |            argument has type `&SomeStruct`
+   |
+help: use `let _ = ...` to ignore the expression or result
+   |
+LL -     forget(&owned);
+LL +     let _ = &owned;
+   |
+
+error: calls to `std::mem::forget` with a reference instead of an owned value does nothing
+  --> $DIR/forgetting_references-can-fixed.rs:15:5
+   |
+LL |     forget(&&owned);
+   |     ^^^^^^^-------^
+   |            |
+   |            argument has type `&&SomeStruct`
+   |
+help: use `let _ = ...` to ignore the expression or result
+   |
+LL -     forget(&&owned);
+LL +     let _ = &&owned;
+   |
+
+error: calls to `std::mem::forget` with a reference instead of an owned value does nothing
+  --> $DIR/forgetting_references-can-fixed.rs:16:5
+   |
+LL |     forget(&mut owned);
+   |     ^^^^^^^----------^
+   |            |
+   |            argument has type `&mut SomeStruct`
+   |
+help: use `let _ = ...` to ignore the expression or result
+   |
+LL -     forget(&mut owned);
+LL +     let _ = &mut owned;
+   |
+
+error: calls to `std::mem::forget` with a reference instead of an owned value does nothing
+  --> $DIR/forgetting_references-can-fixed.rs:20:5
+   |
+LL |     forget(&*reference1);
+   |     ^^^^^^^------------^
+   |            |
+   |            argument has type `&SomeStruct`
+   |
+help: use `let _ = ...` to ignore the expression or result
+   |
+LL -     forget(&*reference1);
+LL +     let _ = &*reference1;
+   |
+
+error: calls to `std::mem::forget` with a reference instead of an owned value does nothing
+  --> $DIR/forgetting_references-can-fixed.rs:23:5
+   |
+LL |     forget(reference2);
+   |     ^^^^^^^----------^
+   |            |
+   |            argument has type `&mut SomeStruct`
+   |
+help: use `let _ = ...` to ignore the expression or result
+   |
+LL -     forget(reference2);
+LL +     let _ = reference2;
+   |
+
+error: calls to `std::mem::forget` with a reference instead of an owned value does nothing
+  --> $DIR/forgetting_references-can-fixed.rs:26:5
+   |
+LL |     forget(reference3);
+   |     ^^^^^^^----------^
+   |            |
+   |            argument has type `&SomeStruct`
+   |
+help: use `let _ = ...` to ignore the expression or result
+   |
+LL -     forget(reference3);
+LL +     let _ = reference3;
+   |
+
+error: calls to `std::mem::forget` with a reference instead of an owned value does nothing
+  --> $DIR/forgetting_references-can-fixed.rs:31:5
+   |
+LL |     forget(&val);
+   |     ^^^^^^^----^
+   |            |
+   |            argument has type `&T`
+   |
+help: use `let _ = ...` to ignore the expression or result
+   |
+LL -     forget(&val);
+LL +     let _ = &val;
+   |
+
+error: calls to `std::mem::forget` with a reference instead of an owned value does nothing
+  --> $DIR/forgetting_references-can-fixed.rs:39:5
+   |
+LL |     std::mem::forget(&SomeStruct);
+   |     ^^^^^^^^^^^^^^^^^-----------^
+   |                      |
+   |                      argument has type `&SomeStruct`
+   |
+help: use `let _ = ...` to ignore the expression or result
+   |
+LL -     std::mem::forget(&SomeStruct);
+LL +     let _ = &SomeStruct;
+   |
+
+error: aborting due to 9 previous errors
+
diff --git a/tests/ui/lint/forgetting_references.rs b/tests/ui/lint/forgetting_references.rs
index ecfa23ee497..d0ec2a77ab1 100644
--- a/tests/ui/lint/forgetting_references.rs
+++ b/tests/ui/lint/forgetting_references.rs
@@ -23,6 +23,16 @@ fn main() {
 
     let ref reference3 = SomeStruct;
     forget(reference3); //~ WARN calls to `std::mem::forget`
+
+    let ref reference4 = SomeStruct;
+
+    let a = 1;
+    match a {
+        1 => forget(&*reference1), //~ WARN calls to `std::mem::forget`
+        2 => forget(reference3), //~ WARN calls to `std::mem::forget`
+        3 => forget(reference4), //~ WARN calls to `std::mem::forget`
+        _ => {}
+    }
 }
 
 #[allow(dead_code)]
diff --git a/tests/ui/lint/forgetting_references.stderr b/tests/ui/lint/forgetting_references.stderr
index 5624b690789..afd5030a680 100644
--- a/tests/ui/lint/forgetting_references.stderr
+++ b/tests/ui/lint/forgetting_references.stderr
@@ -6,12 +6,16 @@ LL |     forget(&SomeStruct);
    |            |
    |            argument has type `&SomeStruct`
    |
-   = note: use `let _ = ...` to ignore the expression or result
 note: the lint level is defined here
   --> $DIR/forgetting_references.rs:3:9
    |
 LL | #![warn(forgetting_references)]
    |         ^^^^^^^^^^^^^^^^^^^^^
+help: use `let _ = ...` to ignore the expression or result
+   |
+LL -     forget(&SomeStruct);
+LL +     let _ = &SomeStruct;
+   |
 
 warning: calls to `std::mem::forget` with a reference instead of an owned value does nothing
   --> $DIR/forgetting_references.rs:13:5
@@ -21,7 +25,11 @@ LL |     forget(&owned);
    |            |
    |            argument has type `&SomeStruct`
    |
-   = note: use `let _ = ...` to ignore the expression or result
+help: use `let _ = ...` to ignore the expression or result
+   |
+LL -     forget(&owned);
+LL +     let _ = &owned;
+   |
 
 warning: calls to `std::mem::forget` with a reference instead of an owned value does nothing
   --> $DIR/forgetting_references.rs:14:5
@@ -31,7 +39,11 @@ LL |     forget(&&owned);
    |            |
    |            argument has type `&&SomeStruct`
    |
-   = note: use `let _ = ...` to ignore the expression or result
+help: use `let _ = ...` to ignore the expression or result
+   |
+LL -     forget(&&owned);
+LL +     let _ = &&owned;
+   |
 
 warning: calls to `std::mem::forget` with a reference instead of an owned value does nothing
   --> $DIR/forgetting_references.rs:15:5
@@ -41,7 +53,11 @@ LL |     forget(&mut owned);
    |            |
    |            argument has type `&mut SomeStruct`
    |
-   = note: use `let _ = ...` to ignore the expression or result
+help: use `let _ = ...` to ignore the expression or result
+   |
+LL -     forget(&mut owned);
+LL +     let _ = &mut owned;
+   |
 
 warning: calls to `std::mem::forget` with a reference instead of an owned value does nothing
   --> $DIR/forgetting_references.rs:19:5
@@ -51,7 +67,11 @@ LL |     forget(&*reference1);
    |            |
    |            argument has type `&SomeStruct`
    |
-   = note: use `let _ = ...` to ignore the expression or result
+help: use `let _ = ...` to ignore the expression or result
+   |
+LL -     forget(&*reference1);
+LL +     let _ = &*reference1;
+   |
 
 warning: calls to `std::mem::forget` with a reference instead of an owned value does nothing
   --> $DIR/forgetting_references.rs:22:5
@@ -61,7 +81,11 @@ LL |     forget(reference2);
    |            |
    |            argument has type `&mut SomeStruct`
    |
-   = note: use `let _ = ...` to ignore the expression or result
+help: use `let _ = ...` to ignore the expression or result
+   |
+LL -     forget(reference2);
+LL +     let _ = reference2;
+   |
 
 warning: calls to `std::mem::forget` with a reference instead of an owned value does nothing
   --> $DIR/forgetting_references.rs:25:5
@@ -71,27 +95,69 @@ LL |     forget(reference3);
    |            |
    |            argument has type `&SomeStruct`
    |
+help: use `let _ = ...` to ignore the expression or result
+   |
+LL -     forget(reference3);
+LL +     let _ = reference3;
+   |
+
+warning: calls to `std::mem::forget` with a reference instead of an owned value does nothing
+  --> $DIR/forgetting_references.rs:31:14
+   |
+LL |         1 => forget(&*reference1),
+   |              ^^^^^^^------------^
+   |                     |
+   |                     argument has type `&SomeStruct`
+   |
+   = note: use `let _ = ...` to ignore the expression or result
+
+warning: calls to `std::mem::forget` with a reference instead of an owned value does nothing
+  --> $DIR/forgetting_references.rs:32:14
+   |
+LL |         2 => forget(reference3),
+   |              ^^^^^^^----------^
+   |                     |
+   |                     argument has type `&SomeStruct`
+   |
+   = note: use `let _ = ...` to ignore the expression or result
+
+warning: calls to `std::mem::forget` with a reference instead of an owned value does nothing
+  --> $DIR/forgetting_references.rs:33:14
+   |
+LL |         3 => forget(reference4),
+   |              ^^^^^^^----------^
+   |                     |
+   |                     argument has type `&SomeStruct`
+   |
    = note: use `let _ = ...` to ignore the expression or result
 
 warning: calls to `std::mem::forget` with a reference instead of an owned value does nothing
-  --> $DIR/forgetting_references.rs:30:5
+  --> $DIR/forgetting_references.rs:40:5
    |
 LL |     forget(&val);
    |     ^^^^^^^----^
    |            |
    |            argument has type `&T`
    |
-   = note: use `let _ = ...` to ignore the expression or result
+help: use `let _ = ...` to ignore the expression or result
+   |
+LL -     forget(&val);
+LL +     let _ = &val;
+   |
 
 warning: calls to `std::mem::forget` with a reference instead of an owned value does nothing
-  --> $DIR/forgetting_references.rs:38:5
+  --> $DIR/forgetting_references.rs:48:5
    |
 LL |     std::mem::forget(&SomeStruct);
    |     ^^^^^^^^^^^^^^^^^-----------^
    |                      |
    |                      argument has type `&SomeStruct`
    |
-   = note: use `let _ = ...` to ignore the expression or result
+help: use `let _ = ...` to ignore the expression or result
+   |
+LL -     std::mem::forget(&SomeStruct);
+LL +     let _ = &SomeStruct;
+   |
 
-warning: 9 warnings emitted
+warning: 12 warnings emitted