Merge pull request #369 from codeodor/patch-1

Improve error message when passed unsupported type

lib/arel/visitors/to_sql.rb

@@ -4,6 +4,12 @@ require 'arel/visitors/reduce'
 
 module Arel
   module Visitors
+    class UnsupportedVisitError < StandardError
+      def initialize(object)
+        super "Unsupported argument type: #{object.class.name}. Construct an Arel node instead."
+      end
+    end
+
     class ToSql < Arel::Visitors::Reduce
       ##
       # This is some roflscale crazy stuff.  I'm roflscaling this because
@@ -737,7 +743,7 @@ module Arel
       end
 
       def unsupported o, collector
-        raise "unsupported: #{o.class.name}"
+        raise UnsupportedVisitError.new(o)
       end
 
       alias :visit_ActiveSupport_Multibyte_Chars :unsupported

test/visitors/test_to_sql.rb

@@ -273,9 +273,9 @@ module Arel
         compile(Nodes.build_quoted(nil)).must_be_like "NULL"
       end
 
-      it "unsupported input should not raise ArgumentError" do
-        error = assert_raises(RuntimeError) { compile(nil) }
-        assert_match(/\Aunsupported/, error.message)
+      it "unsupported input should raise UnsupportedVisitError" do
+        error = assert_raises(UnsupportedVisitError) { compile(nil) }
+        assert_match(/\AUnsupported/, error.message)
       end
 
       it "should visit_Arel_SelectManager, which is a subquery" do