Check types in Formula#==

Comparing two objects should not raise an exception, even if they have
different types.

The semantics of #== are now the same as #eql?, so make one an alias.

Library/Homebrew/formula.rb

@@ -292,12 +292,11 @@ class Formula
     @pin.unpin
   end
 
-  def == b
-    name == b.name
-  end
-  def eql? b
-    self == b and self.class.equal? b.class
+  def == other
+    instance_of?(other.class) && name == other.name
   end
+  alias_method :eql?, :==
+
   def hash
     name.hash
   end

Library/Homebrew/test/test_formula.rb

@@ -124,6 +124,10 @@ class FormulaTests < Test::Unit::TestCase
     assert !y.eql?(x)
   end
 
+  def test_comparison_with_non_formula_objects_does_not_raise
+    assert_not_equal TestBall.new, Object.new
+  end
+
   def test_class_naming
     assert_equal 'ShellFm', Formula.class_s('shell.fm')
     assert_equal 'Fooxx', Formula.class_s('foo++')