Adds sequelize.literal() and sequelize.cast()

sequelize.literal() will tell Sequelize to not escape whatever you type
into the argument, for example:

sequelize.literal('1-2') will result in "1-2" unescaped.

sequelize.cast(input, type) will cast input into type, for example:

sequelize.cast('1-2', 'integer') will result in:

```CAST('1-2' AS INTEGER)```

lib/dialects/abstract/query-generator.js

@@ -281,7 +281,7 @@ module.exports = (function() {
       Objects:
         * If raw is set, that value should be returned verbatim, without quoting
         * If fn is set, the string should start with the value of fn, starting paren, followed by
-          the values of cols (which is assumed to be an array), quoted and joined with ', ', 
+          the values of cols (which is assumed to be an array), quoted and joined with ', ',
           unless they are themselves objects
         * If direction is set, should be prepended
 
@@ -293,7 +293,7 @@ module.exports = (function() {
         return this.quoteIdentifiers(obj, force)
       } else if (Array.isArray(obj)) {
         return this.quote(obj[0], force) + ' ' + obj[1]
-      } else if (obj instanceof Utils.fn || obj instanceof Utils.col) {
+      } else if (obj instanceof Utils.fn || obj instanceof Utils.col || obj instanceof Utils.literal || obj instanceof Utils.cast) {
         return obj.toString(this)
       } else if (Utils._.isObject(obj) && 'raw' in obj) {
         return obj.raw
@@ -363,11 +363,11 @@ module.exports = (function() {
       Escape a value (e.g. a string, number or date)
     */
     escape: function(value, field) {
-      if (value instanceof Utils.fn || value instanceof Utils.col) {
+      if (value instanceof Utils.fn || value instanceof Utils.col || value instanceof Utils.literal || value instanceof Utils.cast) {
         return value.toString(this)
       } else {
-        return SqlString.escape(value, false, null, this.dialect, field)  
-      }       
+        return SqlString.escape(value, false, null, this.dialect, field)
+      }
     }
 
   }

lib/sequelize.js

@@ -363,5 +363,13 @@ module.exports = (function() {
     return new Utils.col(col)
   }
 
+  Sequelize.prototype.cast = function (val, type) {
+    return new Utils.cast(val, type)
+  }
+
+  Sequelize.prototype.literal = function (val) {
+    return new Utils.literal(val)
+  }
+
   return Sequelize
 })()

lib/utils.js

@@ -492,7 +492,31 @@ var Utils = module.exports = {
   },
   col: function (col) {
     this.col = col
+  },
+  cast: function (val, type) {
+    this.val  = val
+    this.type = (type || '').trim()
+  },
+  literal: function (val) {
+    this.val = val
+  }
+}
+
+// I know this may seem silly, but this gives us the ability to recognize whether
+// or not we should be escaping or if we should trust the user. Basically, it
+// keeps things in perspective and organized.
+Utils.literal.prototype.toString = function() {
+  return this.val
+}
+
+Utils.cast.prototype.toString = function(queryGenerator) {
+  if (!this.val instanceof Utils.fn && !this.val instanceof Utils.col && !this.val instanceof Utils.literal) {
+    this.val = queryGenerator.escape(this.val)
+  } else {
+    this.val = this.val.toString(queryGenerator)
   }
+
+  return 'CAST(' + this.val + ' AS ' + this.type.toUpperCase() + ')'
 }
 
 Utils.fn.prototype.toString = function(queryGenerator) {
@@ -501,9 +525,10 @@ Utils.fn.prototype.toString = function(queryGenerator) {
       return arg.toString(queryGenerator)
     } else {
       return queryGenerator.escape(arg)
-    }    
+    }
   }).join(', ') + ')'
 }
+
 Utils.col.prototype.toString = function (queryGenerator) {
   return queryGenerator.quote(this.col)
 }

test/dao-factory.test.js

@@ -383,6 +383,82 @@ describe(Support.getTestDialectTeaser("DAOFactory"), function () {
   })
 
   describe('create', function() {
+    it('is possible to use casting when creating an instance', function (done) {
+      var self = this
+        , type = dialect === "mysql" ? 'signed' : 'integer'
+        , _done = _.after(2, function() {
+          done()
+        })
+
+      this.User.create({
+        intVal: this.sequelize.cast('1', type)
+      }).on('sql', function (sql) {
+        expect(sql).to.match(new RegExp('CAST\\(1 AS ' + type.toUpperCase() + '\\)'))
+        _done()
+      })
+      .success(function (user) {
+        self.User.find(user.id).success(function (user) {
+          expect(user.intVal).to.equal(1)
+          _done()
+        })
+      })
+    })
+
+    it('is possible to use casting multiple times mixed in with other utilities', function (done) {
+      var self  = this
+        , type  = this.sequelize.cast(this.sequelize.cast(this.sequelize.literal('1-2'), 'integer'), 'integer')
+        , _done = _.after(2, function() {
+          done()
+        })
+
+      if (dialect === "mysql") {
+        type = this.sequelize.cast(this.sequelize.cast(this.sequelize.literal('1-2'), 'unsigned'), 'signed')
+      }
+
+      this.User.create({
+        intVal: type
+      }).on('sql', function (sql) {
+        if (dialect === "mysql") {
+          expect(sql).to.contain('CAST(CAST(1-2 AS UNSIGNED) AS SIGNED)')
+        } else {
+          expect(sql).to.contain('CAST(CAST(1-2 AS INTEGER) AS INTEGER)')
+        }
+
+        _done()
+      }).success(function (user) {
+        self.User.find(user.id).success(function (user) {
+          expect(user.intVal).to.equal(-1)
+          _done()
+        })
+      })
+    })
+
+    it('is possible to just use .literal() to bypass escaping', function (done) {
+      var self = this
+
+      this.User.create({
+        intVal: this.sequelize.literal('CAST(1-2 AS ' + (dialect === "mysql" ? 'SIGNED' : 'INTEGER') + ')')
+      }).success(function (user) {
+        self.User.find(user.id).success(function (user) {
+          expect(user.intVal).to.equal(-1)
+          done()
+        })
+      })
+    })
+
+    it('is possible for .literal() to contain other utility functions', function (done) {
+      var self = this
+
+      this.User.create({
+        intVal: this.sequelize.literal(this.sequelize.cast('1-2', (dialect === "mysql" ? 'SIGNED' : 'INTEGER')))
+      }).success(function (user) {
+        self.User.find(user.id).success(function (user) {
+          expect(user.intVal).to.equal(-1)
+          done()
+        })
+      })
+    })
+
     it('is possible to use funtions when creating an instance', function (done) {
       var self = this
       this.User.create({
@@ -394,6 +470,7 @@ describe(Support.getTestDialectTeaser("DAOFactory"), function () {
         })
       })
     })
+
     it('is possible to use functions as default values', function (done) {
       var self = this
         , userWithDefaults
@@ -446,6 +523,7 @@ describe(Support.getTestDialectTeaser("DAOFactory"), function () {
         done()
       }
     })
+
     it("casts empty arrays correctly for postgresql insert", function(done) {
       if (dialect !== "postgres" && dialect !== "postgresql-native") {
         expect('').to.equal('')
@@ -1068,6 +1146,21 @@ describe(Support.getTestDialectTeaser("DAOFactory"), function () {
       })
     })
 
+    it('updates with casting', function (done) {
+      var self = this
+
+      this.User.create({
+        username: 'John'
+      }).success(function(user) {
+        self.User.update({username: self.sequelize.cast('1', 'char')}, {username: 'John'}).success(function() {
+          self.User.all().success(function(users) {
+            expect(users[0].username).to.equal('1')
+            done()
+          })
+        })
+      })
+    })
+
     it('updates with function and column value', function (done) {
       var self = this