Don't use exceptions for control flow

Author: chrisseaton

lib/contracts/call_with.rb

@@ -1,6 +1,10 @@
 module Contracts
   module CallWith
     def call_with(this, *args, &blk)
+      call_with_inner(false, this, *args, &blk)
+    end
+
+    def call_with_inner(returns, this, *args, &blk)
       args << blk if blk
 
       # Explicitly append blk=nil if nil != Proc contract violation anticipated
@@ -16,14 +20,16 @@ def call_with(this, *args, &blk)
         validator = @args_validators[i]
 
         unless validator && validator[arg]
-          return unless Contract.failure_callback(:arg => arg,
-                                                  :contract => contract,
-                                                  :class => klass,
-                                                  :method => method,
-                                                  :contracts => self,
-                                                  :arg_pos => i+1,
-                                                  :total_args => args.size,
-                                                  :return_value => false)
+          data = {:arg => arg,
+                  :contract => contract,
+                  :class => klass,
+                  :method => method,
+                  :contracts => self,
+                  :arg_pos => i+1,
+                  :total_args => args.size,
+                  :return_value => false}
+          return ParamContractError.new("as return value", data) if returns
+          return unless Contract.failure_callback(data)
         end
 
         if contract.is_a?(Contracts::Func) && blk && !nil_block_appended

lib/contracts/method_handler.rb

@@ -125,31 +125,23 @@ def redefine_method
         # function. Otherwise we return the result.
         # If we run out of functions, we raise the last error, but
         # convert it to_contract_error.
-        success = false
-        i = 0
-        result = nil
+
         expected_error = decorated_methods[0].failure_exception
+        last_error = nil
 
-        until success
-          decorated_method = decorated_methods[i]
-          i += 1
-          begin
-            success = true
-            result = decorated_method.call_with(self, *args, &blk)
-          rescue expected_error => error
-            success = false
-            unless decorated_methods[i]
-              begin
-                ::Contract.failure_callback(error.data, false)
-              rescue expected_error => final_error
-                raise final_error.to_contract_error
-              end
-            end
-          end
+        decorated_methods.each do |decorated_method|
+          result = decorated_method.call_with_inner(true, self, *args, &blk)
+          return result unless result.is_a?(ParamContractError)
+          last_error = result
         end
 
-        # Return the result of successfully called method
-        result
+        begin
+          if ::Contract.failure_callback(last_error.data, false)
+            decorated_methods.last.call_with_inner(false, self, *args, &blk)
+          end
+        rescue expected_error => final_error
+          raise final_error.to_contract_error
+        end
       end
     end