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+Two associated items (like methods, associated types, associated functions,
+etc.) were defined with the same identifier.
+
+Erroneous code example:
+
+```compile_fail,E0201
+struct Foo(u8);
+
+impl Foo {
+    fn bar(&self) -> bool { self.0 > 5 }
+    fn bar() {} // error: duplicate associated function
+}
+
+trait Baz {
+    type Quux;
+    fn baz(&self) -> bool;
+}
+
+impl Baz for Foo {
+    type Quux = u32;
+
+    fn baz(&self) -> bool { true }
+
+    // error: duplicate method
+    fn baz(&self) -> bool { self.0 > 5 }
+
+    // error: duplicate associated type
+    type Quux = u32;
+}
+```
+
+Note, however, that items with the same name are allowed for inherent `impl`
+blocks that don't overlap:
+
+```
+struct Foo<T>(T);
+
+impl Foo<u8> {
+    fn bar(&self) -> bool { self.0 > 5 }
+}
+
+impl Foo<bool> {
+    fn bar(&self) -> bool { self.0 }
+}
+```