1 files changed, 55 insertions, 0 deletions
diff --git a/tests/ui/lint/noop-method-call.rs b/tests/ui/lint/noop-method-call.rs
new file mode 100644
index 00000000000..89b29663595
--- /dev/null
+++ b/tests/ui/lint/noop-method-call.rs
@@ -0,0 +1,55 @@
+// check-pass
+
+#![allow(unused)]
+#![warn(noop_method_call)]
+
+use std::borrow::Borrow;
+use std::ops::Deref;
+
+struct PlainType<T>(T);
+
+#[derive(Clone)]
+struct CloneType<T>(T);
+
+fn main() {
+    let non_clone_type_ref = &PlainType(1u32);
+    let non_clone_type_ref_clone: &PlainType<u32> = non_clone_type_ref.clone();
+    //~^ WARNING call to `.clone()` on a reference in this situation does nothing
+
+    let clone_type_ref = &CloneType(1u32);
+    let clone_type_ref_clone: CloneType<u32> = clone_type_ref.clone();
+
+    // Calling clone on a double reference doesn't warn since the method call itself
+    // peels the outer reference off
+    let clone_type_ref = &&CloneType(1u32);
+    let clone_type_ref_clone: &CloneType<u32> = clone_type_ref.clone();
+
+    let non_deref_type = &PlainType(1u32);
+    let non_deref_type_deref: &PlainType<u32> = non_deref_type.deref();
+    //~^ WARNING call to `.deref()` on a reference in this situation does nothing
+
+    // Dereferencing a &&T does not warn since it has collapsed the double reference
+    let non_deref_type = &&PlainType(1u32);
+    let non_deref_type_deref: &PlainType<u32> = non_deref_type.deref();
+
+    let non_borrow_type = &PlainType(1u32);
+    let non_borrow_type_borrow: &PlainType<u32> = non_borrow_type.borrow();
+    //~^ WARNING call to `.borrow()` on a reference in this situation does nothing
+
+    // Borrowing a &&T does not warn since it has collapsed the double reference
+    let non_borrow_type = &&PlainType(1u32);
+    let non_borrow_type_borrow: &PlainType<u32> = non_borrow_type.borrow();
+
+    let xs = ["a", "b", "c"];
+    let _v: Vec<&str> = xs.iter().map(|x| x.clone()).collect(); // ok, but could use `*x` instead
+}
+
+fn generic<T>(non_clone_type: &PlainType<T>) {
+    non_clone_type.clone();
+    //~^ WARNING call to `.clone()` on a reference in this situation does nothing
+}
+
+fn non_generic(non_clone_type: &PlainType<u32>) {
+    non_clone_type.clone();
+    //~^ WARNING call to `.clone()` on a reference in this situation does nothing
+}