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+The `self` keyword was used inside of an associated function without a "`self`
+receiver" parameter.
+
+Erroneous code example:
+
+```compile_fail,E0424
+struct Foo;
+
+impl Foo {
+    // `bar` is a method, because it has a receiver parameter.
+    fn bar(&self) {}
+
+    // `foo` is not a method, because it has no receiver parameter.
+    fn foo() {
+        self.bar(); // error: `self` value is a keyword only available in
+                    //        methods with a `self` parameter
+    }
+}
+```
+
+The `self` keyword can only be used inside methods, which are associated
+functions (functions defined inside of a `trait` or `impl` block) that have a
+`self` receiver as its first parameter, like `self`, `&self`, `&mut self` or
+`self: &mut Pin<Self>` (this last one is an example of an ["arbitrary `self`
+type"](https://github.com/rust-lang/rust/issues/44874)).
+
+Check if the associated function's parameter list should have contained a `self`
+receiver for it to be a method, and add it if so. Example:
+
+```
+struct Foo;
+
+impl Foo {
+    fn bar(&self) {}
+
+    fn foo(self) { // `foo` is now a method.
+        self.bar(); // ok!
+    }
+}
+```