FULL PRODUCT VERSION :
java version "1.8.0_121"
Java(TM) SE Runtime Environment (build 1.8.0_121-b13)
Java HotSpot(TM) 64-Bit Server VM (build 25.121-b13, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Linux 4.8.15-1-MANJARO #1 SMP PREEMPT Thu Dec 15 22:22:45 UTC 2016 x86_64 GNU/Linux

A DESCRIPTION OF THE PROBLEM :
A method is called by passing a lambda expression as single argument. That method is overloaded. The first method takes a java.util.function.Supplier<?> as single argument, the second one expects <T extends java.lang.Number>.

The compiler fails saying that also the second method matches the method reference.

Interestingly, the code does compile when changing <T extends java.lang.Number> to java.lang.Number.

This is probably related to the problem already reported in JDK-8164611, but I wasn't sure if it's exactly the same issue.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Try to compile the code via "javac AmbiguousReferenceTest.java".

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
I'd expected the code to compile and print "success" when run via "java AmbiguousReferenceTest".
ACTUAL -
The code didn't compile (ambiguous reference).

It does compile on Eclipse though and the test prints "success" (as expected).

Eclipse IDE for Java Developers
Version: Neon.2 Release (4.6.2)
Build id: 20161208-0600

ERROR MESSAGES/STACK TRACES THAT OCCUR :
AmbiguousReferenceTest.java:5: error: reference to test is ambiguous
                test(() -> true);
                ^
  both method test(Supplier<Boolean>) in AmbiguousReferenceTest and method <T>test(T) in AmbiguousReferenceTest match
  where T is a type-variable:
    T extends Number declared in method <T>test(T)
1 error

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
public class AmbiguousReferenceTest {

public static void main(String[] args) {
test((java.util.function.Supplier<?>) (() -> true));
test(() -> true);
System.out.println("success");
}

static void test(java.util.function.Supplier<?> obj) {
// fine
}

// with this method the class compiles
// static void test(java.lang.Number obj) {
// throw new AssertionError("shouldn't be called");
// }

// with this method the class doesn't compile
static <T extends java.lang.Number> void test(T obj) {
throw new AssertionError("shouldn't be called");
}
}
---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
Workaround 1: don't use generics in the second method (i.e. the one that shouldn't be called). See commented out lines 14-16.
Workaround 2: cast the argument when calling the method. See line 4.