Unexpected problem during inference

[stephan-herrmann]

This program

			import java.util.function.Function;
			interface C<A> { }
			interface S<T> {
				<A> A m1(C<A> c);
			}
			public abstract class X {
				void foo2(S<String> s) {
					s.m1(m2(String::toUpperCase, xyz -> "NODATA"));
				}
				public abstract <T, K, U>
					C<?> m2(Function<? super T, ? extends K> keyMapper,
							Function<? super T, ? extends U> valueMapper);
			}

triggers these errors:

----------\n
1. ERROR in X.java (at line 8)\n
	s.m1(m2(String::toUpperCase, xyz -> "NODATA"));\n
	     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\n
Problem detected during type inference: Unknown error at invocation of m2(Function<? super Object,? extends Object>, Function<? super Object,? extends Object>)\n
----------\n
2. ERROR in X.java (at line 8)\n
	s.m1(m2(String::toUpperCase, xyz -> "NODATA"));\n
	        ^^^^^^^^^^^^^^^^^^^\n
The type String does not define toUpperCase(Object) that is applicable here\n
----------\n

The first message should of course never be seen.