spec changes for reference conditional expressions

This code:

public class Test {
    void m() {
        //compiles in javac 7, but not in javac 8
        CharSequence bar = foo(true ? String.class : StringBuilder.class);
    }

    static <T> T foo(Class<T> clazz) {
        return null;
    }
}

compiles fine with javac 7 but for 8 it fails with this error message:

Test.java:4: error: method foo in class Test cannot be applied to given types;
        CharSequence bar = foo(true ? String.class : StringBuilder.class);
                           ^
  required: Class<T>
  found: true ? Str[...]class
  reason: inferred type does not conform to equality constraint(s)
    inferred: StringBuilder
    equality constraints(s): StringBuilder,String
  where T is a type-variable:
    T extends Object declared in method <T>foo(Class<T>)
1 error

This is a compatibility issue due to the current spec that should be investigated.

originally reported in SO: http://stackoverflow.com/questions/22509488/generics-compilation-error-with-ternary-operator-in-java-8-but-not-in-java-7