Fix some #eql? correctness issues

The implementation of #eql? and #hash should ensure that if a.eql?(b),
then a.hash == b.hash, but #eql? itself should not *depend* on #hash.

For example, given

  class Thingy
    def eql?
      instance_of?(other.class) && hash == other.hash
    end

    def hash
      [name, *tags].hash
    end
  end

if #hash produces a collision for different values of [name, *tags], two
Thingy objects will appear to be eql?, even though this is not the case.
Instead, #eql? should depend on the equality of name and tags directly.

1 files changed, 1 insertions, 1 deletions

diff --git a/Library/Homebrew/dependency.rb b/Library/Homebrew/dependency.rb
index 05318fc9a..407623810 100644
--- a/Library/Homebrew/dependency.rb
+++ b/Library/Homebrew/dependency.rb
@@ -21,7 +21,7 @@ class Dependency
   end
 
   def eql?(other)
-    instance_of?(other.class) && hash == other.hash
+    instance_of?(other.class) && name == other.name
   end
 
   def hash