2 files changed, 83 insertions, 0 deletions
diff --git a/tests/ui/impl-trait/in-trait/rpitit-duplicate-associated-fn.rs b/tests/ui/impl-trait/in-trait/rpitit-duplicate-associated-fn.rs
new file mode 100644
index 00000000000..4fddd7c4ac8
--- /dev/null
+++ b/tests/ui/impl-trait/in-trait/rpitit-duplicate-associated-fn.rs
@@ -0,0 +1,30 @@
+// issue#140796
+
+trait Bar {
+    fn method() -> impl Sized;
+    fn method() -> impl Sized;  //~ ERROR: the name `method` is defined multiple times
+}
+
+impl Bar for () {               //~ ERROR: not all trait items implemented, missing: `method`
+    fn method() -> impl Sized {
+        42
+    }
+    fn method() -> impl Sized { //~ ERROR: duplicate definitions with name `method`
+        42
+    }
+}
+
+trait T {
+    fn method() -> impl Sized;
+}
+
+impl T for () {
+    fn method() -> impl Sized {
+        42
+    }
+    fn method() -> impl Sized { //~ ERROR: duplicate definitions with name `method`
+        42
+    }
+}
+
+fn main() {}
diff --git a/tests/ui/impl-trait/in-trait/rpitit-duplicate-associated-fn.stderr b/tests/ui/impl-trait/in-trait/rpitit-duplicate-associated-fn.stderr
new file mode 100644
index 00000000000..b58e8136479
--- /dev/null
+++ b/tests/ui/impl-trait/in-trait/rpitit-duplicate-associated-fn.stderr
@@ -0,0 +1,53 @@
+error[E0428]: the name `method` is defined multiple times
+  --> $DIR/rpitit-duplicate-associated-fn.rs:5:5
+   |
+LL |     fn method() -> impl Sized;
+   |     -------------------------- previous definition of the value `method` here
+LL |     fn method() -> impl Sized;
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^ `method` redefined here
+   |
+   = note: `method` must be defined only once in the value namespace of this trait
+
+error[E0201]: duplicate definitions with name `method`:
+  --> $DIR/rpitit-duplicate-associated-fn.rs:12:5
+   |
+LL |       fn method() -> impl Sized;
+   |       -------------------------- item in trait
+...
+LL | /     fn method() -> impl Sized {
+LL | |         42
+LL | |     }
+   | |_____- previous definition here
+LL | /     fn method() -> impl Sized {
+LL | |         42
+LL | |     }
+   | |_____^ duplicate definition
+
+error[E0201]: duplicate definitions with name `method`:
+  --> $DIR/rpitit-duplicate-associated-fn.rs:25:5
+   |
+LL |       fn method() -> impl Sized;
+   |       -------------------------- item in trait
+...
+LL | /     fn method() -> impl Sized {
+LL | |         42
+LL | |     }
+   | |_____- previous definition here
+LL | /     fn method() -> impl Sized {
+LL | |         42
+LL | |     }
+   | |_____^ duplicate definition
+
+error[E0046]: not all trait items implemented, missing: `method`
+  --> $DIR/rpitit-duplicate-associated-fn.rs:8:1
+   |
+LL |     fn method() -> impl Sized;
+   |     -------------------------- `method` from trait
+...
+LL | impl Bar for () {
+   | ^^^^^^^^^^^^^^^ missing `method` in implementation
+
+error: aborting due to 4 previous errors
+
+Some errors have detailed explanations: E0046, E0201, E0428.
+For more information about an error, try `rustc --explain E0046`.