diff --git a/tests/ui/rc_buffer.rs b/tests/ui/rc_buffer.rs
index c8c2bec67..1fa986439 100644
--- a/tests/ui/rc_buffer.rs
+++ b/tests/ui/rc_buffer.rs
@@ -1,13 +1,26 @@
+#![warn(clippy::rc_buffer)]
+
+use std::cell::RefCell;
 use std::ffi::OsString;
 use std::path::PathBuf;
 use std::rc::Rc;
 
-#[warn(clippy::rc_buffer)]
 struct S {
-    a: Rc<String>,
-    b: Rc<PathBuf>,
-    c: Rc<Vec<u8>>,
-    d: Rc<OsString>,
+    // triggers lint
+    bad1: Rc<String>,
+    bad2: Rc<PathBuf>,
+    bad3: Rc<Vec<u8>>,
+    bad4: Rc<OsString>,
+    // does not trigger lint
+    good1: Rc<RefCell<String>>,
 }
 
+// triggers lint
+fn func_bad1(_: Rc<String>) {}
+fn func_bad2(_: Rc<PathBuf>) {}
+fn func_bad3(_: Rc<Vec<u8>>) {}
+fn func_bad4(_: Rc<OsString>) {}
+// does not trigger lint
+fn func_good1(_: Rc<RefCell<String>>) {}
+
 fn main() {}
diff --git a/tests/ui/rc_buffer.stderr b/tests/ui/rc_buffer.stderr
index 641a13a22..e4cc169af 100644
--- a/tests/ui/rc_buffer.stderr
+++ b/tests/ui/rc_buffer.stderr
@@ -1,28 +1,52 @@
 error: usage of `Rc<T>` when T is a buffer type
-  --> $DIR/rc_buffer.rs:7:8
+  --> $DIR/rc_buffer.rs:10:11
    |
-LL |     a: Rc<String>,
-   |        ^^^^^^^^^^ help: try: `Rc<str>`
+LL |     bad1: Rc<String>,
+   |           ^^^^^^^^^^ help: try: `Rc<str>`
    |
    = note: `-D clippy::rc-buffer` implied by `-D warnings`
 
 error: usage of `Rc<T>` when T is a buffer type
-  --> $DIR/rc_buffer.rs:8:8
+  --> $DIR/rc_buffer.rs:11:11
    |
-LL |     b: Rc<PathBuf>,
-   |        ^^^^^^^^^^^ help: try: `Rc<std::path::Path>`
+LL |     bad2: Rc<PathBuf>,
+   |           ^^^^^^^^^^^ help: try: `Rc<std::path::Path>`
 
 error: usage of `Rc<T>` when T is a buffer type
-  --> $DIR/rc_buffer.rs:9:8
+  --> $DIR/rc_buffer.rs:12:11
    |
-LL |     c: Rc<Vec<u8>>,
-   |        ^^^^^^^^^^^ help: try: `Rc<[u8]>`
+LL |     bad3: Rc<Vec<u8>>,
+   |           ^^^^^^^^^^^ help: try: `Rc<[u8]>`
 
 error: usage of `Rc<T>` when T is a buffer type
-  --> $DIR/rc_buffer.rs:10:8
+  --> $DIR/rc_buffer.rs:13:11
    |
-LL |     d: Rc<OsString>,
-   |        ^^^^^^^^^^^^ help: try: `Rc<std::ffi::OsStr>`
+LL |     bad4: Rc<OsString>,
+   |           ^^^^^^^^^^^^ help: try: `Rc<std::ffi::OsStr>`
 
-error: aborting due to 4 previous errors
+error: usage of `Rc<T>` when T is a buffer type
+  --> $DIR/rc_buffer.rs:19:17
+   |
+LL | fn func_bad1(_: Rc<String>) {}
+   |                 ^^^^^^^^^^ help: try: `Rc<str>`
+
+error: usage of `Rc<T>` when T is a buffer type
+  --> $DIR/rc_buffer.rs:20:17
+   |
+LL | fn func_bad2(_: Rc<PathBuf>) {}
+   |                 ^^^^^^^^^^^ help: try: `Rc<std::path::Path>`
+
+error: usage of `Rc<T>` when T is a buffer type
+  --> $DIR/rc_buffer.rs:21:17
+   |
+LL | fn func_bad3(_: Rc<Vec<u8>>) {}
+   |                 ^^^^^^^^^^^ help: try: `Rc<[u8]>`
+
+error: usage of `Rc<T>` when T is a buffer type
+  --> $DIR/rc_buffer.rs:22:17
+   |
+LL | fn func_bad4(_: Rc<OsString>) {}
+   |                 ^^^^^^^^^^^^ help: try: `Rc<std::ffi::OsStr>`
+
+error: aborting due to 8 previous errors
 
diff --git a/tests/ui/rc_buffer_arc.rs b/tests/ui/rc_buffer_arc.rs
index a878b0ab3..5d5865848 100644
--- a/tests/ui/rc_buffer_arc.rs
+++ b/tests/ui/rc_buffer_arc.rs
@@ -1,13 +1,25 @@
+#![warn(clippy::rc_buffer)]
+
 use std::ffi::OsString;
 use std::path::PathBuf;
-use std::sync::Arc;
+use std::sync::{Arc, Mutex};
 
-#[warn(clippy::rc_buffer)]
 struct S {
-    a: Arc<String>,
-    b: Arc<PathBuf>,
-    c: Arc<Vec<u8>>,
-    d: Arc<OsString>,
+    // triggers lint
+    bad1: Arc<String>,
+    bad2: Arc<PathBuf>,
+    bad3: Arc<Vec<u8>>,
+    bad4: Arc<OsString>,
+    // does not trigger lint
+    good1: Arc<Mutex<String>>,
 }
 
+// triggers lint
+fn func_bad1(_: Arc<String>) {}
+fn func_bad2(_: Arc<PathBuf>) {}
+fn func_bad3(_: Arc<Vec<u8>>) {}
+fn func_bad4(_: Arc<OsString>) {}
+// does not trigger lint
+fn func_good1(_: Arc<Mutex<String>>) {}
+
 fn main() {}
diff --git a/tests/ui/rc_buffer_arc.stderr b/tests/ui/rc_buffer_arc.stderr
index c4b016210..8252270d2 100644
--- a/tests/ui/rc_buffer_arc.stderr
+++ b/tests/ui/rc_buffer_arc.stderr
@@ -1,28 +1,52 @@
 error: usage of `Arc<T>` when T is a buffer type
-  --> $DIR/rc_buffer_arc.rs:7:8
+  --> $DIR/rc_buffer_arc.rs:9:11
    |
-LL |     a: Arc<String>,
-   |        ^^^^^^^^^^^ help: try: `Arc<str>`
+LL |     bad1: Arc<String>,
+   |           ^^^^^^^^^^^ help: try: `Arc<str>`
    |
    = note: `-D clippy::rc-buffer` implied by `-D warnings`
 
 error: usage of `Arc<T>` when T is a buffer type
-  --> $DIR/rc_buffer_arc.rs:8:8
+  --> $DIR/rc_buffer_arc.rs:10:11
    |
-LL |     b: Arc<PathBuf>,
-   |        ^^^^^^^^^^^^ help: try: `Arc<std::path::Path>`
+LL |     bad2: Arc<PathBuf>,
+   |           ^^^^^^^^^^^^ help: try: `Arc<std::path::Path>`
 
 error: usage of `Arc<T>` when T is a buffer type
-  --> $DIR/rc_buffer_arc.rs:9:8
+  --> $DIR/rc_buffer_arc.rs:11:11
    |
-LL |     c: Arc<Vec<u8>>,
-   |        ^^^^^^^^^^^^ help: try: `Arc<[u8]>`
+LL |     bad3: Arc<Vec<u8>>,
+   |           ^^^^^^^^^^^^ help: try: `Arc<[u8]>`
 
 error: usage of `Arc<T>` when T is a buffer type
-  --> $DIR/rc_buffer_arc.rs:10:8
+  --> $DIR/rc_buffer_arc.rs:12:11
    |
-LL |     d: Arc<OsString>,
-   |        ^^^^^^^^^^^^^ help: try: `Arc<std::ffi::OsStr>`
+LL |     bad4: Arc<OsString>,
+   |           ^^^^^^^^^^^^^ help: try: `Arc<std::ffi::OsStr>`
 
-error: aborting due to 4 previous errors
+error: usage of `Arc<T>` when T is a buffer type
+  --> $DIR/rc_buffer_arc.rs:18:17
+   |
+LL | fn func_bad1(_: Arc<String>) {}
+   |                 ^^^^^^^^^^^ help: try: `Arc<str>`
+
+error: usage of `Arc<T>` when T is a buffer type
+  --> $DIR/rc_buffer_arc.rs:19:17
+   |
+LL | fn func_bad2(_: Arc<PathBuf>) {}
+   |                 ^^^^^^^^^^^^ help: try: `Arc<std::path::Path>`
+
+error: usage of `Arc<T>` when T is a buffer type
+  --> $DIR/rc_buffer_arc.rs:20:17
+   |
+LL | fn func_bad3(_: Arc<Vec<u8>>) {}
+   |                 ^^^^^^^^^^^^ help: try: `Arc<[u8]>`
+
+error: usage of `Arc<T>` when T is a buffer type
+  --> $DIR/rc_buffer_arc.rs:21:17
+   |
+LL | fn func_bad4(_: Arc<OsString>) {}
+   |                 ^^^^^^^^^^^^^ help: try: `Arc<std::ffi::OsStr>`
+
+error: aborting due to 8 previous errors
 
diff --git a/tests/ui/rc_buffer_redefined_string.rs b/tests/ui/rc_buffer_redefined_string.rs
new file mode 100644
index 000000000..5d31a848c
--- /dev/null
+++ b/tests/ui/rc_buffer_redefined_string.rs
@@ -0,0 +1,12 @@
+#![warn(clippy::rc_buffer)]
+
+use std::rc::Rc;
+
+struct String;
+
+struct S {
+    // does not trigger lint
+    good1: Rc<String>,
+}
+
+fn main() {}
diff --git a/tests/ui/rc_buffer_redefined_string.stderr b/tests/ui/rc_buffer_redefined_string.stderr
new file mode 100644
index 000000000..e69de29bb