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+An attempted implementation of a trait method has the wrong number of function
+parameters.
+
+Erroneous code example:
+
+```compile_fail,E0050
+trait Foo {
+    fn foo(&self, x: u8) -> bool;
+}
+
+struct Bar;
+
+// error: method `foo` has 1 parameter but the declaration in trait `Foo::foo`
+// has 2
+impl Foo for Bar {
+    fn foo(&self) -> bool { true }
+}
+```
+
+For example, the `Foo` trait has a method `foo` with two function parameters
+(`&self` and `u8`), but the implementation of `foo` for the type `Bar` omits
+the `u8` parameter. To fix this error, they must have the same parameters:
+
+```
+trait Foo {
+    fn foo(&self, x: u8) -> bool;
+}
+
+struct Bar;
+
+impl Foo for Bar {
+    fn foo(&self, x: u8) -> bool { // ok!
+        true
+    }
+}
+```