Deprecate usage of should_not raise_error

lib/mspec/expectations/should.rb

@@ -23,6 +23,10 @@ def should_not(matcher = NO_MATCHER_GIVEN)
     raise "should_not outside example" unless state
     MSpec.actions :expectation, state
 
+    if RaiseErrorMatcher === matcher
+      $stderr.puts "\nDeprecation: ->{}.should_not raise_error breaks code style and is deprecated"
+    end
+
     if NO_MATCHER_GIVEN.equal?(matcher)
       SpecNegativeOperatorMatcher.new(self)
     else

spec/expectations/should.rb

@@ -70,4 +70,8 @@ def finish
   it "invokes the MSpec :expectation actions" do
     1.should_not == 2
   end
+
+  it "deprecates using `{}.should_not raise_error`" do
+    -> { }.should_not raise_error
+  end
 end

spec/expectations/should_spec.rb

@@ -5,7 +5,7 @@
   before :all do
     path = RbConfig::CONFIG['bindir']
     exe  = RbConfig::CONFIG['ruby_install_name']
-    file = File.dirname(__FILE__) + '/should.rb'
+    file = File.dirname(__FILE__) + '/should.rb 2>&1'
     @out = `#{path}/#{exe} #{file}`
   end
 
@@ -45,6 +45,10 @@
 No behavior expectation was found in the example
 EOS
     end
+
+    it 'prints a deprecation message about using `{}.should_not raise_error`' do
+      @out.should include "Deprecation: ->{}.should_not raise_error breaks code style and is deprecated"
+    end
   end
 
   it "prints status information" do