Summary

The javac compiler should not accept private method references with a type variable receiver.

Problem

JLS 4.4 specifies that:

The members of a type variable X with bound T & I 1 & ... & I n are the members of
the intersection type (§4.9) T & I 1 & ... & I n appearing at the point where the type
variable is declared.

So code like:

import java.util.function.*;
class Test {
    private String asString() {
        return "bar";
    }

    static <T extends Test> Function<T, String> foo() {
        return T::asString;
    }
}

should be rejected by javac as private method asString is not a member of type variable T

Solution

The proposed solution is to sync javac with the specification so that private method references with type variable receiver are rejected by javac

Specification

No specification changes are required.