added tests

tests/ui/needless_pass_by_ref_mut.rs

@@ -230,6 +230,18 @@ async fn async_vec(b: &mut Vec<bool>) {
 async fn async_vec2(b: &mut Vec<bool>) {
     b.push(true);
 }
+fn non_mut(n: &str) {}
+//Should warn
+pub async fn call_in_closure1(n: &mut str) {
+    (|| non_mut(n))()
+}
+fn str_mut(str: &mut String) -> bool {
+    str.pop().is_some()
+}
+//Should not warn
+pub async fn call_in_closure2(str: &mut String) {
+    (|| str_mut(str))();
+}
 
 // Should not warn.
 pub async fn closure(n: &mut usize) -> impl '_ + FnMut() {

tests/ui/needless_pass_by_ref_mut.stderr

@@ -108,28 +108,36 @@ LL | async fn inner_async3(x: &mut i32, y: &mut u32) {
    |                          ^^^^^^^^ help: consider changing to: `&i32`
 
 error: this argument is a mutable reference, but not used mutably
-  --> $DIR/needless_pass_by_ref_mut.rs:235:25
+  --> $DIR/needless_pass_by_ref_mut.rs:235:34
+   |
+LL | pub async fn call_in_closure1(n: &mut str) {
+   |                                  ^^^^^^^^ help: consider changing to: `&str`
+   |
+   = warning: changing this function will impact semver compatibility
+
+error: this argument is a mutable reference, but not used mutably
+  --> $DIR/needless_pass_by_ref_mut.rs:247:25
    |
 LL | pub async fn closure(n: &mut usize) -> impl '_ + FnMut() {
    |                         ^^^^^^^^^^ help: consider changing to: `&usize`
    |
    = warning: changing this function will impact semver compatibility
 
 error: this argument is a mutable reference, but not used mutably
-  --> $DIR/needless_pass_by_ref_mut.rs:242:20
+  --> $DIR/needless_pass_by_ref_mut.rs:254:20
    |
 LL | pub fn closure2(n: &mut usize) -> impl '_ + FnMut() -> usize {
    |                    ^^^^^^^^^^ help: consider changing to: `&usize`
    |
    = warning: changing this function will impact semver compatibility
 
 error: this argument is a mutable reference, but not used mutably
-  --> $DIR/needless_pass_by_ref_mut.rs:253:26
+  --> $DIR/needless_pass_by_ref_mut.rs:265:26
    |
 LL | pub async fn closure4(n: &mut usize) {
    |                          ^^^^^^^^^^ help: consider changing to: `&usize`
    |
    = warning: changing this function will impact semver compatibility
 
-error: aborting due to 20 previous errors
+error: aborting due to 21 previous errors