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+The `self` parameter in a method has an invalid "receiver type".
+
+Erroneous code example:
+
+```compile_fail,E0307
+struct Foo;
+struct Bar;
+
+trait Trait {
+    fn foo(&self);
+}
+
+impl Trait for Foo {
+    fn foo(self: &Bar) {}
+}
+```
+
+Methods take a special first parameter, of which there are three variants:
+`self`, `&self`, and `&mut self`. These are syntactic sugar for
+`self: Self`, `self: &Self`, and `self: &mut Self` respectively.
+
+```
+# struct Foo;
+trait Trait {
+    fn foo(&self);
+//         ^^^^^ `self` here is a reference to the receiver object
+}
+
+impl Trait for Foo {
+    fn foo(&self) {}
+//         ^^^^^ the receiver type is `&Foo`
+}
+```
+
+The type `Self` acts as an alias to the type of the current trait
+implementer, or "receiver type". Besides the already mentioned `Self`,
+`&Self` and `&mut Self` valid receiver types, the following are also valid:
+`self: Box<Self>`, `self: Rc<Self>`, `self: Arc<Self>`, and `self: Pin<P>`
+(where P is one of the previous types except `Self`). Note that `Self` can
+also be the underlying implementing type, like `Foo` in the following
+example:
+
+```
+# struct Foo;
+# trait Trait {
+#     fn foo(&self);
+# }
+impl Trait for Foo {
+    fn foo(self: &Foo) {}
+}
+```
+
+This error will be emitted by the compiler when using an invalid receiver type,
+like in the following example:
+
+```compile_fail,E0307
+# struct Foo;
+# struct Bar;
+# trait Trait {
+#     fn foo(&self);
+# }
+impl Trait for Foo {
+    fn foo(self: &Bar) {}
+}
+```
+
+The nightly feature [Arbitrary self types][AST] extends the accepted
+set of receiver types to also include any type that can dereference to
+`Self`:
+
+```
+#![feature(arbitrary_self_types)]
+
+struct Foo;
+struct Bar;
+
+// Because you can dereference `Bar` into `Foo`...
+impl std::ops::Deref for Bar {
+    type Target = Foo;
+
+    fn deref(&self) -> &Foo {
+        &Foo
+    }
+}
+
+impl Foo {
+    fn foo(self: Bar) {}
+//         ^^^^^^^^^ ...it can be used as the receiver type
+}
+```
+
+[AST]: https://doc.rust-lang.org/unstable-book/language-features/arbitrary-self-types.html