| The following code is fine in Java 7, but poses a problem in Java 8. |
| |
| ```java |
| static class A { |
| B c(D d) { return null; } |
| static B c(A a, D d) { return null; } |
| } |
| ``` |
| |
| The method reference `A::c` of the instance method `c` has an implicit first |
| parameter for the `this` pointer. So both methods that `A::c` could resolve to |
| are compatible with `BiFunction<A, D, B>`, and the method reference is |
| ambiguous. |
| |
| ```java |
| void f(BiFunction<A, D, B> f) { ... } |
| ``` |
| |
| ``` |
| error: incompatible types: invalid method reference |
| f(A::c); |
| ^ |
| reference to c is ambiguous |
| both method c(A,D) in A and method c(D) in A match |
| ``` |
| |
| Consider renaming one of the methods to avoid the ambiguity. |
