Auto merge of #12843 - mdm:fix-unnecessary-to-owned-println-interaction, r=y21

Fix `unnecessary_to_owned` interaction with macro expansion

fixes #12821

In the case of an unnecessary `.iter().cloned()`, the lint `unnecessary_to_owned` might suggest to remove the `&` from references without checking if such references are inside a macro expansion. This can lead to unexpected behavior or even broken code if the lint suggestion is applied blindly. See issue #12821 for an example.

This PR checks if such references are inside macro expansions and skips this part of the lint suggestion in these cases.

changelog: [`unnecessary_to_owned`]: Don't suggest to remove `&` inside macro expansion

tests/ui/unnecessary_iter_cloned.fixed

@@ -170,3 +170,32 @@ fn check_mut_iteratee_and_modify_inner_variable() {
         }
     }
 }
+
+mod issue_12821 {
+    fn foo() {
+        let v: Vec<_> = "hello".chars().collect();
+        for c in v.iter() {
+            //~^ ERROR: unnecessary use of `cloned`
+            println!("{c}"); // should not suggest to remove `&`
+        }
+    }
+
+    fn bar() {
+        let v: Vec<_> = "hello".chars().collect();
+        for c in v.iter() {
+            //~^ ERROR: unnecessary use of `cloned`
+            let ref_c = c; //~ HELP: remove any references to the binding
+            println!("{ref_c}");
+        }
+    }
+
+    fn baz() {
+        let v: Vec<_> = "hello".chars().enumerate().collect();
+        for (i, c) in v.iter() {
+            //~^ ERROR: unnecessary use of `cloned`
+            let ref_c = c; //~ HELP: remove any references to the binding
+            let ref_i = i;
+            println!("{i} {ref_c}"); // should not suggest to remove `&` from `i`
+        }
+    }
+}

tests/ui/unnecessary_iter_cloned.rs

@@ -170,3 +170,32 @@ fn check_mut_iteratee_and_modify_inner_variable() {
         }
     }
 }
+
+mod issue_12821 {
+    fn foo() {
+        let v: Vec<_> = "hello".chars().collect();
+        for c in v.iter().cloned() {
+            //~^ ERROR: unnecessary use of `cloned`
+            println!("{c}"); // should not suggest to remove `&`
+        }
+    }
+
+    fn bar() {
+        let v: Vec<_> = "hello".chars().collect();
+        for c in v.iter().cloned() {
+            //~^ ERROR: unnecessary use of `cloned`
+            let ref_c = &c; //~ HELP: remove any references to the binding
+            println!("{ref_c}");
+        }
+    }
+
+    fn baz() {
+        let v: Vec<_> = "hello".chars().enumerate().collect();
+        for (i, c) in v.iter().cloned() {
+            //~^ ERROR: unnecessary use of `cloned`
+            let ref_c = &c; //~ HELP: remove any references to the binding
+            let ref_i = &i;
+            println!("{i} {ref_c}"); // should not suggest to remove `&` from `i`
+        }
+    }
+}

tests/ui/unnecessary_iter_cloned.stderr

@@ -10,7 +10,7 @@ help: use
    |
 LL |     for (t, path) in files {
    |                      ~~~~~
-help: remove this `&`
+help: remove any references to the binding
    |
 LL -         let other = match get_file_path(&t) {
 LL +         let other = match get_file_path(t) {
@@ -26,11 +26,49 @@ help: use
    |
 LL |     for (t, path) in files.iter() {
    |                      ~~~~~~~~~~~~
-help: remove this `&`
+help: remove any references to the binding
    |
 LL -         let other = match get_file_path(&t) {
 LL +         let other = match get_file_path(t) {
    |
 
-error: aborting due to 2 previous errors
+error: unnecessary use of `cloned`
+  --> tests/ui/unnecessary_iter_cloned.rs:177:18
+   |
+LL |         for c in v.iter().cloned() {
+   |                  ^^^^^^^^^^^^^^^^^ help: use: `v.iter()`
+
+error: unnecessary use of `cloned`
+  --> tests/ui/unnecessary_iter_cloned.rs:185:18
+   |
+LL |         for c in v.iter().cloned() {
+   |                  ^^^^^^^^^^^^^^^^^
+   |
+help: use
+   |
+LL |         for c in v.iter() {
+   |                  ~~~~~~~~
+help: remove any references to the binding
+   |
+LL -             let ref_c = &c;
+LL +             let ref_c = c;
+   |
+
+error: unnecessary use of `cloned`
+  --> tests/ui/unnecessary_iter_cloned.rs:194:23
+   |
+LL |         for (i, c) in v.iter().cloned() {
+   |                       ^^^^^^^^^^^^^^^^^
+   |
+help: use
+   |
+LL |         for (i, c) in v.iter() {
+   |                       ~~~~~~~~
+help: remove any references to the binding
+   |
+LL ~             let ref_c = c;
+LL ~             let ref_i = i;
+   |
+
+error: aborting due to 5 previous errors
 

tests/ui/unnecessary_to_owned.stderr

@@ -487,7 +487,7 @@ help: use
    |
 LL |     for t in file_types {
    |              ~~~~~~~~~~
-help: remove this `&`
+help: remove any references to the binding
    |
 LL -         let path = match get_file_path(&t) {
 LL +         let path = match get_file_path(t) {