1 files changed, 51 insertions, 0 deletions
diff --git a/src/tools/clippy/tests/ui/no_effect_replace.rs b/src/tools/clippy/tests/ui/no_effect_replace.rs
new file mode 100644
index 000000000..ad17d53f7
--- /dev/null
+++ b/src/tools/clippy/tests/ui/no_effect_replace.rs
@@ -0,0 +1,51 @@
+#![warn(clippy::no_effect_replace)]
+
+fn main() {
+    let _ = "12345".replace('1', "1");
+    let _ = "12345".replace("12", "12");
+    let _ = String::new().replace("12", "12");
+
+    let _ = "12345".replacen('1', "1", 1);
+    let _ = "12345".replacen("12", "12", 1);
+    let _ = String::new().replacen("12", "12", 1);
+
+    let _ = "12345".replace("12", "22");
+    let _ = "12345".replacen("12", "22", 1);
+
+    let mut x = X::default();
+    let _ = "hello".replace(&x.f(), &x.f());
+    let _ = "hello".replace(&x.f(), &x.ff());
+
+    let _ = "hello".replace(&y(), &y());
+    let _ = "hello".replace(&y(), &z());
+
+    let _ = Replaceme.replace("a", "a");
+}
+
+#[derive(Default)]
+struct X {}
+
+impl X {
+    fn f(&mut self) -> String {
+        "he".to_string()
+    }
+
+    fn ff(&mut self) -> String {
+        "hh".to_string()
+    }
+}
+
+fn y() -> String {
+    "he".to_string()
+}
+
+fn z() -> String {
+    "hh".to_string()
+}
+
+struct Replaceme;
+impl Replaceme {
+    pub fn replace(&mut self, a: &str, b: &str) -> Self {
+        Self
+    }
+}