1 == new Object() throws ClassCastException

In the corner case of a Comparable instance being comparedTo an Object instance, the comparison made by DefaultTypeTransformation#compareToWithEqualityCheck() was becoming Object.isAssignableFrom(SomeComparableClass), which was not really serving any purpose, because all classes are assignable to Object. This meaningless condition was causing the issue in both the reported scenarios and has been fixed now.

There seems to be a broader issue here: DefaultTypeTransformation.compareToWithEqualityCheck() assumes that instances of assignment-compatible classes are comparable. I don't think this assumption is safe, even for classes that obey the Comparable contract. For example:

class Foo implements Comparable<Foo> {
  int compareTo(Object other) {
    if (other.getClass() != Foo.class) throw new ClassCastException()
    0
  }
  
  boolean equals(Object other) {
      other.getClass() == Foo.class  
  }
}

class Bar extends Foo implements Comparable<Bar> {
  int compareTo(Object other) {
    if (other.getClass() != Bar.class) throw new ClassCastException()
    0
  }
  
  boolean equals(Object other) {
    other.getClass() == Bar.class  
  }
}

new Foo() == new Bar() // ClassCastException!

A potential ramification of this change is this failing test when the equals and Comparable interface exist in the same class.

// Groovy 1.8 b4
class EqualsCompareTest extends GroovyTestCase {

void test_equals_along() { assert new EqualsOnly() == 1 }

void test_equals_and_compare() { assert new EqualsAndCompare() == 1 }
}

class EqualsOnly {
boolean equals(value) { 1 == value }
}

class EqualsAndCompare implements Comparable {
boolean equals(value) { 1 == value } }
int compareTo(value) { 1.compareTo(value) }
}