Fix raise error when the expectation target is an error instance.

This closes #232

Signed-off-by: Sam Phippen <[email protected]>

Changelog.md

@@ -18,6 +18,8 @@ Bug fixes
   integers (Sam Phippen).
 * Fix `have` matcher to handle the fact that on ruby 2.0,
   `Enumerator#size` may return nil (Kenta Murata).
+* Fix `expect { raise s }.to raise_error(s)` where s is an error instance
+  (Sam Phippen).
 
 ### 2.13.0 / 2013-02-23
 [full changelog](http://github.com/rspec/rspec-expectations/compare/v2.12.1...v2.13.0)

lib/rspec/matchers/built_in/raise_error.rb

@@ -20,7 +20,7 @@ def matches?(given_proc, negative_expectation = false)
           @eval_block_passed = false
           begin
             given_proc.call
-          rescue @expected_error => @actual_error
+          rescue expected_error_class => @actual_error
             @raised_expected_error = true
             @with_expected_message = verify_message
           rescue Exception => @actual_error
@@ -76,6 +76,10 @@ def description
 
         private
 
+        def expected_error_class
+          (@expected_error.is_a? Class) ? @expected_error : @expected_error.class
+        end
+
         def expected_error
           case @expected_message
           when nil

spec/rspec/matchers/raise_error_spec.rb

@@ -10,6 +10,11 @@
     expect {raise}.to raise_error
   end
 
+  it "passes if an error instance is expected" do
+    s = StandardError.new
+    expect {raise s}.to raise_error(s)
+  end
+
   it "fails if nothing is raised" do
     expect {
       expect {}.to raise_error