diff --git a/clippy_lints/src/needless_pass_by_ref_mut.rs b/clippy_lints/src/needless_pass_by_ref_mut.rs
index 30d3e86dc4ed..9e47c3ad0b7f 100644
--- a/clippy_lints/src/needless_pass_by_ref_mut.rs
+++ b/clippy_lints/src/needless_pass_by_ref_mut.rs
@@ -83,7 +83,9 @@ fn should_skip<'tcx>(
     }
 
     if is_self(arg) {
-        return true;
+        // Interestingly enough, `self` arguments make `is_from_proc_macro` return `true`, hence why
+        // we return early here.
+        return false;
     }
 
     if let PatKind::Binding(.., name, _) = arg.pat.kind {
@@ -185,7 +187,7 @@ impl<'tcx> LateLintPass<'tcx> for NeedlessPassByRefMut<'tcx> {
         }
         // Collect variables mutably used and spans which will need dereferencings from the
         // function body.
-        let MutablyUsedVariablesCtxt { mutably_used_vars, .. } = {
+        let mutably_used_vars = {
             let mut ctx = MutablyUsedVariablesCtxt {
                 mutably_used_vars: HirIdSet::default(),
                 prev_bind: None,
@@ -217,7 +219,7 @@ impl<'tcx> LateLintPass<'tcx> for NeedlessPassByRefMut<'tcx> {
                     check_closures(&mut ctx, cx, &infcx, &mut checked_closures, async_closures);
                 }
             }
-            ctx
+            ctx.generate_mutably_used_ids_from_aliases()
         };
         for ((&input, &_), arg) in it {
             // Only take `&mut` arguments.
@@ -309,12 +311,22 @@ struct MutablyUsedVariablesCtxt<'tcx> {
 }
 
 impl<'tcx> MutablyUsedVariablesCtxt<'tcx> {
-    fn add_mutably_used_var(&mut self, mut used_id: HirId) {
-        while let Some(id) = self.aliases.get(&used_id) {
+    fn add_mutably_used_var(&mut self, used_id: HirId) {
+        self.mutably_used_vars.insert(used_id);
+    }
+
+    // Because the alias may come after the mutable use of a variable, we need to fill the map at
+    // the end.
+    fn generate_mutably_used_ids_from_aliases(mut self) -> HirIdSet {
+        let all_ids = self.mutably_used_vars.iter().copied().collect::<Vec<_>>();
+        for mut used_id in all_ids {
+            while let Some(id) = self.aliases.get(&used_id) {
+                self.mutably_used_vars.insert(used_id);
+                used_id = *id;
+            }
             self.mutably_used_vars.insert(used_id);
-            used_id = *id;
         }
-        self.mutably_used_vars.insert(used_id);
+        self.mutably_used_vars
     }
 
     fn would_be_alias_cycle(&self, alias: HirId, mut target: HirId) -> bool {
diff --git a/tests/ui/needless_pass_by_ref_mut.rs b/tests/ui/needless_pass_by_ref_mut.rs
index a92197fb0af5..3f5f55f40020 100644
--- a/tests/ui/needless_pass_by_ref_mut.rs
+++ b/tests/ui/needless_pass_by_ref_mut.rs
@@ -44,18 +44,13 @@ fn non_mut_ref(_: &Vec<u32>) {}
 struct Bar;
 
 impl Bar {
-    // Should not warn on `&mut self`.
     fn bar(&mut self) {}
+    //~^ ERROR: this argument is a mutable reference, but not used mutably
 
     fn mushroom(&self, vec: &mut Vec<i32>) -> usize {
         //~^ ERROR: this argument is a mutable reference, but not used mutably
         vec.len()
     }
-
-    fn badger(&mut self, vec: &mut Vec<i32>) -> usize {
-        //~^ ERROR: this argument is a mutable reference, but not used mutably
-        vec.len()
-    }
 }
 
 trait Babar {
@@ -307,6 +302,41 @@ fn filter_copy<T: Copy>(predicate: &mut impl FnMut(T) -> bool) -> impl FnMut(&T)
     move |&item| predicate(item)
 }
 
+trait MutSelfTrait {
+    // Should not warn since it's a trait method.
+    fn mut_self(&mut self);
+}
+
+struct MutSelf {
+    a: u32,
+}
+
+impl MutSelf {
+    fn bar(&mut self) {}
+    //~^ ERROR: this argument is a mutable reference, but not used mutably
+    async fn foo(&mut self, u: &mut i32, v: &mut u32) {
+        //~^ ERROR: this argument is a mutable reference, but not used mutably
+        //~| ERROR: this argument is a mutable reference, but not used mutably
+        async {
+            *u += 1;
+        }
+        .await;
+    }
+    async fn foo2(&mut self, u: &mut i32, v: &mut u32) {
+        //~^ ERROR: this argument is a mutable reference, but not used mutably
+        async {
+            self.a += 1;
+            *u += 1;
+        }
+        .await;
+    }
+}
+
+impl MutSelfTrait for MutSelf {
+    // Should not warn since it's a trait method.
+    fn mut_self(&mut self) {}
+}
+
 // `is_from_proc_macro` stress tests
 fn _empty_tup(x: &mut (())) {}
 fn _single_tup(x: &mut ((i32,))) {}
diff --git a/tests/ui/needless_pass_by_ref_mut.stderr b/tests/ui/needless_pass_by_ref_mut.stderr
index 89dad3e60b14..21ca393dcb63 100644
--- a/tests/ui/needless_pass_by_ref_mut.stderr
+++ b/tests/ui/needless_pass_by_ref_mut.stderr
@@ -14,73 +14,73 @@ LL | fn foo6(s: &mut Vec<u32>) {
    |            ^^^^^^^^^^^^^ help: consider changing to: `&Vec<u32>`
 
 error: this argument is a mutable reference, but not used mutably
-  --> tests/ui/needless_pass_by_ref_mut.rs:50:29
+  --> tests/ui/needless_pass_by_ref_mut.rs:47:12
    |
-LL |     fn mushroom(&self, vec: &mut Vec<i32>) -> usize {
-   |                             ^^^^^^^^^^^^^ help: consider changing to: `&Vec<i32>`
+LL |     fn bar(&mut self) {}
+   |            ^^^^^^^^^ help: consider changing to: `&self`
 
 error: this argument is a mutable reference, but not used mutably
-  --> tests/ui/needless_pass_by_ref_mut.rs:55:31
+  --> tests/ui/needless_pass_by_ref_mut.rs:50:29
    |
-LL |     fn badger(&mut self, vec: &mut Vec<i32>) -> usize {
-   |                               ^^^^^^^^^^^^^ help: consider changing to: `&Vec<i32>`
+LL |     fn mushroom(&self, vec: &mut Vec<i32>) -> usize {
+   |                             ^^^^^^^^^^^^^ help: consider changing to: `&Vec<i32>`
 
 error: this argument is a mutable reference, but not used mutably
-  --> tests/ui/needless_pass_by_ref_mut.rs:132:16
+  --> tests/ui/needless_pass_by_ref_mut.rs:127:16
    |
 LL | async fn a1(x: &mut i32) {
    |                ^^^^^^^^ help: consider changing to: `&i32`
 
 error: this argument is a mutable reference, but not used mutably
-  --> tests/ui/needless_pass_by_ref_mut.rs:136:16
+  --> tests/ui/needless_pass_by_ref_mut.rs:131:16
    |
 LL | async fn a2(x: &mut i32, y: String) {
    |                ^^^^^^^^ help: consider changing to: `&i32`
 
 error: this argument is a mutable reference, but not used mutably
-  --> tests/ui/needless_pass_by_ref_mut.rs:140:16
+  --> tests/ui/needless_pass_by_ref_mut.rs:135:16
    |
 LL | async fn a3(x: &mut i32, y: String, z: String) {
    |                ^^^^^^^^ help: consider changing to: `&i32`
 
 error: this argument is a mutable reference, but not used mutably
-  --> tests/ui/needless_pass_by_ref_mut.rs:144:16
+  --> tests/ui/needless_pass_by_ref_mut.rs:139:16
    |
 LL | async fn a4(x: &mut i32, y: i32) {
    |                ^^^^^^^^ help: consider changing to: `&i32`
 
 error: this argument is a mutable reference, but not used mutably
-  --> tests/ui/needless_pass_by_ref_mut.rs:148:24
+  --> tests/ui/needless_pass_by_ref_mut.rs:143:24
    |
 LL | async fn a5(x: i32, y: &mut i32) {
    |                        ^^^^^^^^ help: consider changing to: `&i32`
 
 error: this argument is a mutable reference, but not used mutably
-  --> tests/ui/needless_pass_by_ref_mut.rs:152:24
+  --> tests/ui/needless_pass_by_ref_mut.rs:147:24
    |
 LL | async fn a6(x: i32, y: &mut i32) {
    |                        ^^^^^^^^ help: consider changing to: `&i32`
 
 error: this argument is a mutable reference, but not used mutably
-  --> tests/ui/needless_pass_by_ref_mut.rs:156:32
+  --> tests/ui/needless_pass_by_ref_mut.rs:151:32
    |
 LL | async fn a7(x: i32, y: i32, z: &mut i32) {
    |                                ^^^^^^^^ help: consider changing to: `&i32`
 
 error: this argument is a mutable reference, but not used mutably
-  --> tests/ui/needless_pass_by_ref_mut.rs:160:24
+  --> tests/ui/needless_pass_by_ref_mut.rs:155:24
    |
 LL | async fn a8(x: i32, a: &mut i32, y: i32, z: &mut i32) {
    |                        ^^^^^^^^ help: consider changing to: `&i32`
 
 error: this argument is a mutable reference, but not used mutably
-  --> tests/ui/needless_pass_by_ref_mut.rs:160:45
+  --> tests/ui/needless_pass_by_ref_mut.rs:155:45
    |
 LL | async fn a8(x: i32, a: &mut i32, y: i32, z: &mut i32) {
    |                                             ^^^^^^^^ help: consider changing to: `&i32`
 
 error: this argument is a mutable reference, but not used mutably
-  --> tests/ui/needless_pass_by_ref_mut.rs:194:16
+  --> tests/ui/needless_pass_by_ref_mut.rs:189:16
    |
 LL | fn cfg_warn(s: &mut u32) {}
    |                ^^^^^^^^ help: consider changing to: `&u32`
@@ -88,7 +88,7 @@ LL | fn cfg_warn(s: &mut u32) {}
    = note: this is cfg-gated and may require further changes
 
 error: this argument is a mutable reference, but not used mutably
-  --> tests/ui/needless_pass_by_ref_mut.rs:200:20
+  --> tests/ui/needless_pass_by_ref_mut.rs:195:20
    |
 LL |     fn cfg_warn(s: &mut u32) {}
    |                    ^^^^^^^^ help: consider changing to: `&u32`
@@ -96,19 +96,19 @@ LL |     fn cfg_warn(s: &mut u32) {}
    = note: this is cfg-gated and may require further changes
 
 error: this argument is a mutable reference, but not used mutably
-  --> tests/ui/needless_pass_by_ref_mut.rs:214:39
+  --> tests/ui/needless_pass_by_ref_mut.rs:209:39
    |
 LL | async fn inner_async2(x: &mut i32, y: &mut u32) {
    |                                       ^^^^^^^^ help: consider changing to: `&u32`
 
 error: this argument is a mutable reference, but not used mutably
-  --> tests/ui/needless_pass_by_ref_mut.rs:222:26
+  --> tests/ui/needless_pass_by_ref_mut.rs:217:26
    |
 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
-  --> tests/ui/needless_pass_by_ref_mut.rs:241:34
+  --> tests/ui/needless_pass_by_ref_mut.rs:236:34
    |
 LL | pub async fn call_in_closure1(n: &mut str) {
    |                                  ^^^^^^^^ help: consider changing to: `&str`
@@ -116,15 +116,7 @@ LL | pub async fn call_in_closure1(n: &mut str) {
    = warning: changing this function will impact semver compatibility
 
 error: this argument is a mutable reference, but not used mutably
-  --> tests/ui/needless_pass_by_ref_mut.rs:253:25
-   |
-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
-  --> tests/ui/needless_pass_by_ref_mut.rs:260:20
+  --> tests/ui/needless_pass_by_ref_mut.rs:255:20
    |
 LL | pub fn closure2(n: &mut usize) -> impl '_ + FnMut() -> usize {
    |                    ^^^^^^^^^^ help: consider changing to: `&usize`
@@ -132,7 +124,7 @@ LL | pub fn closure2(n: &mut usize) -> impl '_ + FnMut() -> usize {
    = warning: changing this function will impact semver compatibility
 
 error: this argument is a mutable reference, but not used mutably
-  --> tests/ui/needless_pass_by_ref_mut.rs:271:26
+  --> tests/ui/needless_pass_by_ref_mut.rs:266:26
    |
 LL | pub async fn closure4(n: &mut usize) {
    |                          ^^^^^^^^^^ help: consider changing to: `&usize`
@@ -140,64 +132,88 @@ LL | pub async fn closure4(n: &mut usize) {
    = warning: changing this function will impact semver compatibility
 
 error: this argument is a mutable reference, but not used mutably
-  --> tests/ui/needless_pass_by_ref_mut.rs:311:18
+  --> tests/ui/needless_pass_by_ref_mut.rs:315:12
+   |
+LL |     fn bar(&mut self) {}
+   |            ^^^^^^^^^ help: consider changing to: `&self`
+
+error: this argument is a mutable reference, but not used mutably
+  --> tests/ui/needless_pass_by_ref_mut.rs:317:18
+   |
+LL |     async fn foo(&mut self, u: &mut i32, v: &mut u32) {
+   |                  ^^^^^^^^^ help: consider changing to: `&self`
+
+error: this argument is a mutable reference, but not used mutably
+  --> tests/ui/needless_pass_by_ref_mut.rs:317:45
+   |
+LL |     async fn foo(&mut self, u: &mut i32, v: &mut u32) {
+   |                                             ^^^^^^^^ help: consider changing to: `&u32`
+
+error: this argument is a mutable reference, but not used mutably
+  --> tests/ui/needless_pass_by_ref_mut.rs:325:46
+   |
+LL |     async fn foo2(&mut self, u: &mut i32, v: &mut u32) {
+   |                                              ^^^^^^^^ help: consider changing to: `&u32`
+
+error: this argument is a mutable reference, but not used mutably
+  --> tests/ui/needless_pass_by_ref_mut.rs:341:18
    |
 LL | fn _empty_tup(x: &mut (())) {}
    |                  ^^^^^^^^^ help: consider changing to: `&()`
 
 error: this argument is a mutable reference, but not used mutably
-  --> tests/ui/needless_pass_by_ref_mut.rs:312:19
+  --> tests/ui/needless_pass_by_ref_mut.rs:342:19
    |
 LL | fn _single_tup(x: &mut ((i32,))) {}
    |                   ^^^^^^^^^^^^^ help: consider changing to: `&(i32,)`
 
 error: this argument is a mutable reference, but not used mutably
-  --> tests/ui/needless_pass_by_ref_mut.rs:313:18
+  --> tests/ui/needless_pass_by_ref_mut.rs:343:18
    |
 LL | fn _multi_tup(x: &mut ((i32, u32))) {}
    |                  ^^^^^^^^^^^^^^^^^ help: consider changing to: `&(i32, u32)`
 
 error: this argument is a mutable reference, but not used mutably
-  --> tests/ui/needless_pass_by_ref_mut.rs:314:11
+  --> tests/ui/needless_pass_by_ref_mut.rs:344:11
    |
 LL | fn _fn(x: &mut (fn())) {}
    |           ^^^^^^^^^^^ help: consider changing to: `&fn()`
 
 error: this argument is a mutable reference, but not used mutably
-  --> tests/ui/needless_pass_by_ref_mut.rs:316:23
+  --> tests/ui/needless_pass_by_ref_mut.rs:346:23
    |
 LL | fn _extern_rust_fn(x: &mut extern "Rust" fn()) {}
    |                       ^^^^^^^^^^^^^^^^^^^^^^^ help: consider changing to: `&extern "Rust" fn()`
 
 error: this argument is a mutable reference, but not used mutably
-  --> tests/ui/needless_pass_by_ref_mut.rs:317:20
+  --> tests/ui/needless_pass_by_ref_mut.rs:347:20
    |
 LL | fn _extern_c_fn(x: &mut extern "C" fn()) {}
    |                    ^^^^^^^^^^^^^^^^^^^^ help: consider changing to: `&extern "C" fn()`
 
 error: this argument is a mutable reference, but not used mutably
-  --> tests/ui/needless_pass_by_ref_mut.rs:318:18
+  --> tests/ui/needless_pass_by_ref_mut.rs:348:18
    |
 LL | fn _unsafe_fn(x: &mut unsafe fn()) {}
    |                  ^^^^^^^^^^^^^^^^ help: consider changing to: `&unsafe fn()`
 
 error: this argument is a mutable reference, but not used mutably
-  --> tests/ui/needless_pass_by_ref_mut.rs:319:25
+  --> tests/ui/needless_pass_by_ref_mut.rs:349:25
    |
 LL | fn _unsafe_extern_fn(x: &mut unsafe extern "C" fn()) {}
    |                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider changing to: `&unsafe extern "C" fn()`
 
 error: this argument is a mutable reference, but not used mutably
-  --> tests/ui/needless_pass_by_ref_mut.rs:320:20
+  --> tests/ui/needless_pass_by_ref_mut.rs:350:20
    |
 LL | fn _fn_with_arg(x: &mut unsafe extern "C" fn(i32)) {}
    |                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider changing to: `&unsafe extern "C" fn(i32)`
 
 error: this argument is a mutable reference, but not used mutably
-  --> tests/ui/needless_pass_by_ref_mut.rs:321:20
+  --> tests/ui/needless_pass_by_ref_mut.rs:351:20
    |
 LL | fn _fn_with_ret(x: &mut unsafe extern "C" fn() -> (i32)) {}
    |                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider changing to: `&unsafe extern "C" fn() -> (i32)`
 
-error: aborting due to 31 previous errors
+error: aborting due to 34 previous errors
 
diff --git a/tests/ui/needless_pass_by_ref_mut2.fixed b/tests/ui/needless_pass_by_ref_mut2.fixed
new file mode 100644
index 000000000000..3c2576213cd7
--- /dev/null
+++ b/tests/ui/needless_pass_by_ref_mut2.fixed
@@ -0,0 +1,24 @@
+// If both `inner_async3` and `inner_async4` are present, aliases are declared after
+// they're used in `inner_async4` for some reasons... This test ensures that no
+// only `v` is marked as not used mutably in `inner_async4`.
+
+#![allow(clippy::redundant_closure_call)]
+#![warn(clippy::needless_pass_by_ref_mut)]
+
+pub async fn inner_async3(x: &i32, y: &mut u32) {
+    //~^ ERROR: this argument is a mutable reference, but not used mutably
+    async {
+        *y += 1;
+    }
+    .await;
+}
+
+pub async fn inner_async4(u: &mut i32, v: &u32) {
+    //~^ ERROR: this argument is a mutable reference, but not used mutably
+    async {
+        *u += 1;
+    }
+    .await;
+}
+
+fn main() {}
diff --git a/tests/ui/needless_pass_by_ref_mut2.rs b/tests/ui/needless_pass_by_ref_mut2.rs
new file mode 100644
index 000000000000..34b0b564deb8
--- /dev/null
+++ b/tests/ui/needless_pass_by_ref_mut2.rs
@@ -0,0 +1,24 @@
+// If both `inner_async3` and `inner_async4` are present, aliases are declared after
+// they're used in `inner_async4` for some reasons... This test ensures that no
+// only `v` is marked as not used mutably in `inner_async4`.
+
+#![allow(clippy::redundant_closure_call)]
+#![warn(clippy::needless_pass_by_ref_mut)]
+
+pub async fn inner_async3(x: &mut i32, y: &mut u32) {
+    //~^ ERROR: this argument is a mutable reference, but not used mutably
+    async {
+        *y += 1;
+    }
+    .await;
+}
+
+pub async fn inner_async4(u: &mut i32, v: &mut u32) {
+    //~^ ERROR: this argument is a mutable reference, but not used mutably
+    async {
+        *u += 1;
+    }
+    .await;
+}
+
+fn main() {}
diff --git a/tests/ui/needless_pass_by_ref_mut2.stderr b/tests/ui/needless_pass_by_ref_mut2.stderr
new file mode 100644
index 000000000000..c87536032256
--- /dev/null
+++ b/tests/ui/needless_pass_by_ref_mut2.stderr
@@ -0,0 +1,20 @@
+error: this argument is a mutable reference, but not used mutably
+  --> tests/ui/needless_pass_by_ref_mut2.rs:8:30
+   |
+LL | pub async fn inner_async3(x: &mut i32, y: &mut u32) {
+   |                              ^^^^^^^^ help: consider changing to: `&i32`
+   |
+   = warning: changing this function will impact semver compatibility
+   = note: `-D clippy::needless-pass-by-ref-mut` implied by `-D warnings`
+   = help: to override `-D warnings` add `#[allow(clippy::needless_pass_by_ref_mut)]`
+
+error: this argument is a mutable reference, but not used mutably
+  --> tests/ui/needless_pass_by_ref_mut2.rs:16:43
+   |
+LL | pub async fn inner_async4(u: &mut i32, v: &mut u32) {
+   |                                           ^^^^^^^^ help: consider changing to: `&u32`
+   |
+   = warning: changing this function will impact semver compatibility
+
+error: aborting due to 2 previous errors
+