Don't override let definitions with argument matchers

see #102

ArgumentMatchers (together with ExampleMethods) were
included into the ExampleGroup instance's metaclass.
This caused argument matcher methods such as boolean()
or hash_containing() to override let definitions with
the same name.

This commit fixes this bug by including
ArgumentMatchers into the example group's class and
not into the metaclass.

Changelog.md

@@ -24,6 +24,11 @@ Enhancement:
 * Allow the `have_received` matcher to use a block to set further expectations
   on arguments. (Tim Cowlishaw)
 
+Bug Fixes:
+
+* ArgumentMatcher methods (e.g. `hash_containing`) no longer overwrite
+  `let`-definitions of the same name. (Michi Huber)
+
 ### 2.14.1 / 2013-07-07
 [full changelog](http://github.com/rspec/rspec-mocks/compare/v2.14.0...v2.14.1)
 

lib/rspec/mocks.rb

@@ -8,9 +8,7 @@ class << self
       attr_accessor :space
 
       def setup(host)
-        (class << host; self; end).class_exec do
-          include RSpec::Mocks::ExampleMethods
-        end
+        host.class.class_exec { include RSpec::Mocks::ExampleMethods }
         self.space ||= RSpec::Mocks::Space.new
       end
 

spec/rspec/mocks/mock_spec.rb

@@ -662,6 +662,19 @@ def add_call
       end
     end
 
+    describe "ArgumentMatchers not overriding let definitions" do
+      WithMatchers = Class.new { include RSpec::Mocks::ArgumentMatchers }
+      methods = WithMatchers.new.methods - Object.new.methods
+
+      methods.each do |method|
+        let(method) { :a_thing }
+
+        it "doesn't override a let named #{ method }" do
+          expect(send(method)).to be(:a_thing)
+        end
+      end
+    end
+
     describe 'string representation generated by #to_s' do
       it 'does not contain < because that might lead to invalid HTML in some situations' do
         double = double("Dog")