Check inner caller for clone and judge whether they are mutable

if immutbale -> lint delete redudant clone
if mutable   -> lint check whether clone is needed

tests/ui/unnecessary_iter_cloned.fixed

@@ -21,6 +21,8 @@ fn main() {
     let _ = check_files_ref_mut(&[(FileType::Account, path)]);
     let _ = check_files_self_and_arg(&[(FileType::Account, path)]);
     let _ = check_files_mut_path_buf(&[(FileType::Account, std::path::PathBuf::new())]);
+
+    check_mut_iteratee_and_modify_inner_variable();
 }
 
 // `check_files` and its variants are based on:
@@ -138,3 +140,33 @@ fn check_files_mut_path_buf(files: &[(FileType, std::path::PathBuf)]) -> bool {
 fn get_file_path(_file_type: &FileType) -> Result<std::path::PathBuf, std::io::Error> {
     Ok(std::path::PathBuf::new())
 }
+
+// Issue 12098
+// https://github.com/rust-lang/rust-clippy/issues/12098
+// no message emits
+fn check_mut_iteratee_and_modify_inner_variable() {
+    struct Test {
+        list: Vec<String>,
+        mut_this: bool,
+    }
+
+    impl Test {
+        fn list(&self) -> &[String] {
+            &self.list
+        }
+    }
+
+    let mut test = Test {
+        list: vec![String::from("foo"), String::from("bar")],
+        mut_this: false,
+    };
+
+    for _item in test.list().to_vec() {
+        println!("{}", _item);
+
+        test.mut_this = true;
+        {
+            test.mut_this = true;
+        }
+    }
+}

tests/ui/unnecessary_iter_cloned.rs

@@ -21,6 +21,8 @@ fn main() {
     let _ = check_files_ref_mut(&[(FileType::Account, path)]);
     let _ = check_files_self_and_arg(&[(FileType::Account, path)]);
     let _ = check_files_mut_path_buf(&[(FileType::Account, std::path::PathBuf::new())]);
+
+    check_mut_iteratee_and_modify_inner_variable();
 }
 
 // `check_files` and its variants are based on:
@@ -138,3 +140,33 @@ fn check_files_mut_path_buf(files: &[(FileType, std::path::PathBuf)]) -> bool {
 fn get_file_path(_file_type: &FileType) -> Result<std::path::PathBuf, std::io::Error> {
     Ok(std::path::PathBuf::new())
 }
+
+// Issue 12098
+// https://github.com/rust-lang/rust-clippy/issues/12098
+// no message emits
+fn check_mut_iteratee_and_modify_inner_variable() {
+    struct Test {
+        list: Vec<String>,
+        mut_this: bool,
+    }
+
+    impl Test {
+        fn list(&self) -> &[String] {
+            &self.list
+        }
+    }
+
+    let mut test = Test {
+        list: vec![String::from("foo"), String::from("bar")],
+        mut_this: false,
+    };
+
+    for _item in test.list().to_vec() {
+        println!("{}", _item);
+
+        test.mut_this = true;
+        {
+            test.mut_this = true;
+        }
+    }
+}

tests/ui/unnecessary_iter_cloned.stderr

@@ -1,5 +1,5 @@
 error: unnecessary use of `copied`
-  --> tests/ui/unnecessary_iter_cloned.rs:29:22
+  --> tests/ui/unnecessary_iter_cloned.rs:31:22
    |
 LL |     for (t, path) in files.iter().copied() {
    |                      ^^^^^^^^^^^^^^^^^^^^^
@@ -17,7 +17,7 @@ LL +         let other = match get_file_path(t) {
    |
 
 error: unnecessary use of `copied`
-  --> tests/ui/unnecessary_iter_cloned.rs:44:22
+  --> tests/ui/unnecessary_iter_cloned.rs:46:22
    |
 LL |     for (t, path) in files.iter().copied() {
    |                      ^^^^^^^^^^^^^^^^^^^^^