more tightly spec WrappedModule, and ensure WM#source_location doesn't raise

lib/pry/wrapped_module.rb

@@ -114,10 +114,12 @@ class Pry
     # cannot be found this method returns `nil`.
     #
     # @param [Module] mod The module (or class).
-    # @return [Array<String, Fixnum>] The source location of the
-    #   module (or class).
+    # @return [Array<String, Fixnum>, nil] The source location of the
+    #   module (or class), or `nil` if no source location found.
     def source_location
       @source_location ||= primary_candidate.source_location
+    rescue Pry::RescuableException
+      nil
     end
 
     # @return [String, nil] The associated file for the module (i.e

test/test_wrapped_module.rb

@@ -23,6 +23,9 @@ describe Pry::WrappedModule do
           def test6
           end
         end
+
+        class ForeverAlone
+        end
       end
     end
 
@@ -30,6 +33,10 @@ describe Pry::WrappedModule do
       it 'should return the correct number of candidates' do
         Pry::WrappedModule(Host::CandidateTest).number_of_candidates.should == 3
       end
+
+      it 'should return 0 candidates for a class with no methods and no other definitions' do
+        Pry::WrappedModule(Host::ForeverAlone).number_of_candidates.should == 0
+      end
     end
 
     describe "ordering of candidates" do
@@ -50,6 +57,17 @@ describe Pry::WrappedModule do
       end
     end
 
+    describe "source_location" do
+      it 'should return primary candidates source_location by default' do
+        wm = Pry::WrappedModule(Host::CandidateTest)
+        wm.source_location.should == wm.candidate(0).source_location
+      end
+
+      it 'should return nil if no source_location can be found' do
+        Pry::WrappedModule(Host::ForeverAlone).source_location.should == nil
+      end
+    end
+
     describe "source" do
       it 'should return primary candidates source by default' do
         wm = Pry::WrappedModule(Host::CandidateTest)