Input source:

import java.util.function.Supplier;
public class MethRefBug2 {

    static class Foo<T> {
        static int zero() {
            return 0;
        }
    }

    static void consume(int x) { }
    static void consume(boolean x) { }

    static <T> T grabFrom(Supplier<? extends T> supplier) {
        return supplier.get();
    }

    public static void main(String[] args) {
        consume(grabFrom(Foo::zero));
    }
}

This should compile, but instead you get this error:

MethRefBug2.java:18: error: reference to consume is ambiguous
        consume(grabFrom(Foo::zero));
        ^
  both method consume(int) in MethRefBug2 and method consume(boolean) in MethRefBug2 match
1 error

Clearly consume(boolean) is not a valid option, so this error is bogus.

If you change "boolean" to "Boolean" you get a different (wrong) error:

MethRefBug2.java:18: error: method consume in class MethRefBug2 cannot be applied to given types;
        consume(grabFrom(Foo::zero));
               ^
  required: Boolean
  found: Integer
  reason: argument mismatch; inference variable T has incompatible bounds
      upper bounds: Boolean,Object
      lower bounds: Integer
  where T is a type-variable:
    T extends Object declared in method <T>grabFrom(Supplier<? extends T>)
1 error

All of this goes away if you change "static class Foo<T>" to "static class Foo", even though how the compiler handles a static method reference should (in theory) not be affected at all by whether the class containing that static method is generic or not.