FULL PRODUCT VERSION :
Picked up JAVA_TOOL_OPTIONS: -Dfile.encoding=UTF-8
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 :
OS X 10.11.6

A DESCRIPTION OF THE PROBLEM :
There seams to be differences in how inference is handled between "Function" and "Supplier". I would expect the two examples to conform (see "Actual Result") to the same result. Either a compile error, or not...

Note! The latest version of IntelliJ (2016.3.3) does not give me a warning on this (in the editor)...

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Try to compile the provided source code.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
A successful compile
ACTUAL -
 InferenceTest.a(
                InferenceTest::c,
                name -> new Builder<>(new Gamma()));

...does not compile, while:

        InferenceTest.b(
                InferenceTest::c,
                () -> new Builder<>(new Gamma()));

...does

ERROR MESSAGES/STACK TRACES THAT OCCUR :
Error:(8, 22) java: method a in class InferenceTest cannot be applied to given types;
  required: java.util.function.Function<B,java.lang.String>,java.util.function.Function<java.lang.String,B>
  found: InferenceTest::c,(name)->ne[...]ma())
  reason: inferred type does not conform to upper bound(s)
    inferred: InferenceTest.Builder<InferenceTest.Alfa>
    upper bound(s): InferenceTest.Builder<InferenceTest.Alfa>,InferenceTest.Builder<? extends InferenceTest.Beta>

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
import java.util.function.Function;
import java.util.function.Supplier;

public class InferenceTest {

    public static void main(String[] args) {
        //compile error
        InferenceTest.a(
                InferenceTest::c,
                name -> new Builder<>(new Gamma()));

        //successfully compiles
        InferenceTest.b(
                InferenceTest::c,
                () -> new Builder<>(new Gamma()));
    }

    static <T extends Alfa, B extends Builder<T>> void a(
            final Function<B, String> f1,
            final Function<String, B> f2) {

    }

    static <T extends Alfa, B extends Builder<T>> void b(
            final Function<B, String> f1,
            final Supplier<B> s1) {

    }

    private static String c(final Builder<? extends Beta> builder){return "";}

    public static class Alfa {}
    public static class Beta extends Alfa {}
    public static class Gamma extends Beta {}

    public static class Builder<T> {
        private final T t;

        public Builder(T t) {
            this.t = t;
        }
    }
}

---------- END SOURCE ----------