diff --git a/lib/6to5/builders.js b/lib/6to5/builders.js
deleted file mode 100644
index b015dbc0f0..0000000000
--- a/lib/6to5/builders.js
+++ /dev/null
@@ -1,46 +0,0 @@
-var _ = require("lodash");
-
-var build = function (type, keys) {
-  return function () {
-    var args = arguments;
-    var node = { type: type };
-    _.each(keys, function (key, i) {
-      node[key] = args[i];
-    });
-    return node;
-  };
-};
-
-exports.identifier = build("Identifier", ["name"]);
-
-exports.literal = build("Literal", ["value"]);
-
-exports.functionExpression = build("FunctionExpression", ["id", "params", "body"]);
-
-exports.returnStatement = build("ReturnStatement", ["argument"]);
-
-exports.assignmentExpression = build("AssignmentExpression", ["operator", "left", "right"]);
-
-exports.ifStatement = build("IfStatement", ["test", "consequent", "alternate"]);
-
-exports.callExpression = build("CallExpression", ["callee", "arguments"]);
-
-exports.blockStatement = build("BlockStatement", ["body"]);
-
-exports.memberExpression = build("MemberExpression", ["object", "property", "computed"]);
-
-exports.variableDeclaration = build("VariableDeclaration", ["kind", "declarations"]);
-
-exports.variableDeclarator = build("VariableDeclarator", ["id", "init"]);
-
-exports.arrayExpression = build("ArrayExpression", ["elements"]);
-
-exports.binaryExpression = build("BinaryExpression", ["operator", "left", "right"]);
-
-exports.expressionStatement = build("ExpressionStatement", ["expression"]);
-
-exports.thisExpression = build("ThisExpression");
-
-exports.objectExpression = build("ObjectExpression", ["properties"]);
-
-exports.property = build("Property", ["kind", "key", "value"]);
diff --git a/lib/6to5/file.js b/lib/6to5/file.js
index eec4ec6044..39c08f83a6 100644
--- a/lib/6to5/file.js
+++ b/lib/6to5/file.js
@@ -6,7 +6,7 @@ var transform = require("./transform");
 var generate  = require("./generator");
 var acorn     = require("acorn-6to5");
 var util      = require("./util");
-var b         = require("./builders");
+var t         = require("./types");
 var _         = require("lodash");
 
 function File(opts) {
@@ -72,7 +72,7 @@ File.prototype.addDeclaration = function (name) {
   var declar = this.declarations[name];
   if (declar) return declar.uid;
 
-  var uid = b.identifier(this.generateUid(name));
+  var uid = t.identifier(this.generateUid(name));
   this.declarations[name] = {
     uid: uid,
     node: util.template(name)
diff --git a/lib/6to5/generators/jsx.js b/lib/6to5/generators/jsx.js
index 3544da04ac..fa3ba6e3e7 100644
--- a/lib/6to5/generators/jsx.js
+++ b/lib/6to5/generators/jsx.js
@@ -78,5 +78,5 @@ exports.XJSClosingElement = function (node, print) {
 };
 
 exports.XJSEmptyExpression = function () {
-
+  this.push("null");
 };
diff --git a/lib/6to5/modules/amd.js b/lib/6to5/modules/amd.js
index 65e23f157c..6d8fe2a228 100644
--- a/lib/6to5/modules/amd.js
+++ b/lib/6to5/modules/amd.js
@@ -3,7 +3,6 @@ module.exports = AMDFormatter;
 var CommonJSFormatter = require("./common");
 var util              = require("../util");
 var t                 = require("../types");
-var b                 = require("../builders");
 var _                 = require("lodash");
 
 function AMDFormatter(file) {
@@ -19,21 +18,21 @@ AMDFormatter.prototype.transform = function (ast) {
 
   // build an array of module names
 
-  var names = [b.literal("exports")];
+  var names = [t.literal("exports")];
   _.each(this.ids, function (id, name) {
-    names.push(b.literal(name));
+    names.push(t.literal(name));
   });
-  names = b.arrayExpression(names);
+  names = t.arrayExpression(names);
 
   // build up define container
 
   var params = _.values(this.ids);
-  params.unshift(b.identifier("exports"));
+  params.unshift(t.identifier("exports"));
 
-  var container = b.functionExpression(null, params, b.blockStatement(body));
-  var call = b.callExpression(b.identifier("define"), [names, container]);
+  var container = t.functionExpression(null, params, t.blockStatement(body));
+  var call = t.callExpression(t.identifier("define"), [names, container]);
 
-  program.body = [b.expressionStatement(call)];
+  program.body = [t.expressionStatement(call)];
 };
 
 AMDFormatter.prototype._push = function (node) {
@@ -43,7 +42,7 @@ AMDFormatter.prototype._push = function (node) {
   if (ids[id]) {
     return ids[id];
   } else {
-    return this.ids[id] = b.identifier(this.file.generateUid(id));
+    return this.ids[id] = t.identifier(this.file.generateUid(id));
   }
 };
 
@@ -57,7 +56,7 @@ AMDFormatter.prototype.importSpecifier = function (specifier, node, nodes) {
 
   // import foo from "foo";
   if (specifier.default) {
-    id = b.identifier("default");
+    id = t.identifier("default");
   }
 
   var ref;
@@ -67,11 +66,11 @@ AMDFormatter.prototype.importSpecifier = function (specifier, node, nodes) {
     ref = this._push(node);
   } else {
     // import foo from "foo";
-    ref = b.memberExpression(this._push(node), id, false);
+    ref = t.memberExpression(this._push(node), id, false);
   }
 
-  nodes.push(b.variableDeclaration("var", [
-    b.variableDeclarator(key, ref)
+  nodes.push(t.variableDeclaration("var", [
+    t.variableDeclarator(key, ref)
   ]));
 };
 
diff --git a/lib/6to5/modules/common.js b/lib/6to5/modules/common.js
index 6fe4131d4e..4a6839a3ad 100644
--- a/lib/6to5/modules/common.js
+++ b/lib/6to5/modules/common.js
@@ -2,7 +2,6 @@ module.exports = CommonJSFormatter;
 
 var util = require("../util");
 var t    = require("../types");
-var b    = require("../builders");
 
 function CommonJSFormatter(file) {
   this.file = file;
@@ -20,7 +19,7 @@ CommonJSFormatter.prototype.importSpecifier = function (specifier, node, nodes)
 
   // import foo from "foo";
   if (specifier.default) {
-    specifier.id = b.identifier("default");
+    specifier.id = t.identifier("default");
   }
 
   var templateName = "require-assign";
@@ -100,6 +99,6 @@ CommonJSFormatter.prototype._exportSpecifier = function (getRef, specifier, node
 
 CommonJSFormatter.prototype.exportSpecifier = function (specifier, node, nodes) {
   return this._exportSpecifier(function () {
-    return b.callExpression(b.identifier("require"), [node.source]);
+    return t.callExpression(t.identifier("require"), [node.source]);
   }, specifier, node, nodes);
 };
diff --git a/lib/6to5/modules/umd.js b/lib/6to5/modules/umd.js
index ccb3d1ab87..d90774cbce 100644
--- a/lib/6to5/modules/umd.js
+++ b/lib/6to5/modules/umd.js
@@ -2,7 +2,7 @@ module.exports = UMDFormatter;
 
 var AMDFormatter = require("./amd");
 var util         = require("../util");
-var b            = require("../builders");
+var t            = require("../types");
 var _            = require("lodash");
 
 function UMDFormatter(file) {
@@ -20,28 +20,28 @@ UMDFormatter.prototype.transform = function (ast) {
 
   var names = [];
   _.each(this.ids, function (id, name) {
-    names.push(b.literal(name));
+    names.push(t.literal(name));
   });
 
   // factory
 
   var ids  = _.values(this.ids);
-  var args = [b.identifier("exports")].concat(ids);
+  var args = [t.identifier("exports")].concat(ids);
 
-  var factory = b.functionExpression(null, args, b.blockStatement(body));
+  var factory = t.functionExpression(null, args, t.blockStatement(body));
 
   // runner
 
   var runner = util.template("umd-runner-body", {
-    AMD_ARGUMENTS: b.arrayExpression([b.literal("exports")].concat(names)),
+    AMD_ARGUMENTS: t.arrayExpression([t.literal("exports")].concat(names)),
 
     COMMON_ARGUMENTS: names.map(function (name) {
-      return b.callExpression(b.identifier("require"), [name]);
+      return t.callExpression(t.identifier("require"), [name]);
     })
   });
 
   //
 
-  var call = b.callExpression(runner, [factory]);
-  program.body = [b.expressionStatement(call)];
+  var call = t.callExpression(runner, [factory]);
+  program.body = [t.expressionStatement(call)];
 };
diff --git a/lib/6to5/transformers/_declarations.js b/lib/6to5/transformers/_declarations.js
index 0090aa3d50..d6cf091dd5 100644
--- a/lib/6to5/transformers/_declarations.js
+++ b/lib/6to5/transformers/_declarations.js
@@ -1,12 +1,12 @@
-var b = require("../builders");
+var t = require("../types");
 var _ = require("lodash");
 
 module.exports = function (ast, file) {
   var body = ast.program.body;
 
   _.each(file.declarations, function (declar) {
-    body.unshift(b.variableDeclaration("var", [
-      b.variableDeclarator(declar.uid, declar.node)
+    body.unshift(t.variableDeclaration("var", [
+      t.variableDeclarator(declar.uid, declar.node)
     ]));
   });
 };
diff --git a/lib/6to5/transformers/classes.js b/lib/6to5/transformers/classes.js
index 628f09ff03..e651870d6e 100644
--- a/lib/6to5/transformers/classes.js
+++ b/lib/6to5/transformers/classes.js
@@ -1,12 +1,11 @@
 var traverse = require("../traverse");
 var util     = require("../util");
-var b        = require("../builders");
 var t        = require("../types");
 var _        = require("lodash");
 
 exports.ClassDeclaration = function (node, parent, file) {
-  return b.variableDeclaration("var", [
-    b.variableDeclarator(node.id, buildClass(node, file))
+  return t.variableDeclaration("var", [
+    t.variableDeclarator(node.id, buildClass(node, file))
   ]);
 };
 
@@ -23,7 +22,7 @@ var getMemberExpressionObject = function (node) {
 
 var buildClass = function (node, file) {
   var superName = node.superClass;
-  var className = node.id || b.identifier(file.generateUid("class"));
+  var className = node.id || t.identifier(file.generateUid("class"));
 
   var superClassArgument = node.superClass;
   var superClassCallee   = node.superClass;
@@ -33,7 +32,7 @@ var buildClass = function (node, file) {
       superClassArgument = superClassCallee = getMemberExpressionObject(superName);
     } else if (!t.isIdentifier(superName)) {
       superClassArgument = superName;
-      superClassCallee   = superName = b.identifier(file.generateUid("ref"));
+      superClassCallee   = superName = t.identifier(file.generateUid("ref"));
     }
   }
 
@@ -50,7 +49,7 @@ var buildClass = function (node, file) {
   var returnStatement = body.pop();
 
   if (superName) {
-    body.push(b.expressionStatement(b.callExpression(file.addDeclaration("extends"), [className, superName])));
+    body.push(t.expressionStatement(t.callExpression(file.addDeclaration("extends"), [className, superName])));
 
     container.arguments.push(superClassArgument);
     container.callee.params.push(superClassCallee);
@@ -95,7 +94,7 @@ var buildClassBody = function (file, construct, body, className, superName, node
 
       if (kind === "") {
         kind = "value";
-        util.pushMutatorMap(mutatorMap, methodName, "writable", b.identifier("true"));
+        util.pushMutatorMap(mutatorMap, methodName, "writable", t.identifier("true"));
       }
 
       util.pushMutatorMap(mutatorMap, methodName, kind, node);
@@ -124,13 +123,13 @@ var buildClassBody = function (file, construct, body, className, superName, node
   }
 
   if (instanceProps || staticProps) {
-    staticProps = staticProps || b.literal(null);
+    staticProps = staticProps || t.literal(null);
 
     var args = [className, staticProps];
     if (instanceProps) args.push(instanceProps);
 
-    body.push(b.expressionStatement(
-      b.callExpression(file.addDeclaration("class-props"), args)
+    body.push(t.expressionStatement(
+      t.callExpression(file.addDeclaration("class-props"), args)
     ));
   }
 };
@@ -140,32 +139,32 @@ var superIdentifier = function (superName, methodNode, methodName, node, parent)
     return;
   } else if (t.isCallExpression(parent) && parent.callee === node) {
     // super(); -> ClassName.prototype.MethodName.call(this);
-    parent.arguments.unshift(b.thisExpression());
+    parent.arguments.unshift(t.thisExpression());
 
     if (methodName === "constructor") {
       // constructor() { super(); }
-      return b.memberExpression(superName, b.identifier("call"));
+      return t.memberExpression(superName, t.identifier("call"));
     } else {
       node = superName;
 
       // foo() { super(); }
       if (!methodNode.static) {
-        node = b.memberExpression(node, b.identifier("prototype"));
+        node = t.memberExpression(node, t.identifier("prototype"));
       }
 
-      node = b.memberExpression(node, b.identifier(methodName));
-      return b.memberExpression(node, b.identifier("call"));
+      node = t.memberExpression(node, t.identifier(methodName));
+      return t.memberExpression(node, t.identifier("call"));
     }
   } else if (t.isMemberExpression(parent) && !methodNode.static) {
     // super.test -> ClassName.prototype.test
-    return b.memberExpression(superName, b.identifier("prototype"));
+    return t.memberExpression(superName, t.identifier("prototype"));
   } else {
     return superName;
   }
 };
 
 var replaceInstanceSuperReferences = function (superName, method, methodNode, methodName) {
-  superName = superName || b.identifier("Function");
+  superName = superName || t.identifier("Function");
 
   traverse(method, function (node, parent) {
     if (t.isIdentifier(node) && node.name === "super") {
@@ -177,7 +176,7 @@ var replaceInstanceSuperReferences = function (superName, method, methodNode, me
 
       //  super.test(); -> ClassName.prototype.MethodName.call(this);
       callee.property.name = callee.property.name + ".call";
-      node.arguments.unshift(b.thisExpression());
+      node.arguments.unshift(t.thisExpression());
     }
   });
 };
diff --git a/lib/6to5/transformers/computed-property-names.js b/lib/6to5/transformers/computed-property-names.js
index 1aeb9bcaa1..185503db86 100644
--- a/lib/6to5/transformers/computed-property-names.js
+++ b/lib/6to5/transformers/computed-property-names.js
@@ -1,5 +1,5 @@
 var util = require("../util");
-var b    = require("../builders");
+var t    = require("../types");
 var _    = require("lodash");
 
 exports.ObjectExpression = function (node, parent, file) {
@@ -33,10 +33,10 @@ exports.ObjectExpression = function (node, parent, file) {
 
   _.each(computed, function (prop) {
     containerBody.unshift(
-      b.expressionStatement(
-        b.assignmentExpression(
+      t.expressionStatement(
+        t.assignmentExpression(
           "=",
-          b.memberExpression(objId, prop.key, true),
+          t.memberExpression(objId, prop.key, true),
           prop.value
         )
       )
diff --git a/lib/6to5/transformers/destructuring.js b/lib/6to5/transformers/destructuring.js
index 3e987d602f..c57f0c7acf 100644
--- a/lib/6to5/transformers/destructuring.js
+++ b/lib/6to5/transformers/destructuring.js
@@ -1,13 +1,12 @@
-var b = require("../builders");
 var t = require("../types");
 var _ = require("lodash");
 
 var buildVariableAssign = function (kind, id, init) {
   if (kind === false) {
-    return b.expressionStatement(b.assignmentExpression("=", id, init));
+    return t.expressionStatement(t.assignmentExpression("=", id, init));
   } else {
-    return b.variableDeclaration(kind, [
-      b.variableDeclarator(id, init)
+    return t.variableDeclaration(kind, [
+      t.variableDeclarator(id, init)
     ]);
   }
 };
@@ -27,7 +26,7 @@ var push = function (kind, nodes, elem, parentId) {
 var pushObjectPattern = function (kind, nodes, pattern, parentId) {
   _.each(pattern.properties, function (prop) {
     var pattern2   = prop.value;
-    var patternId2 = b.memberExpression(parentId, prop.key);
+    var patternId2 = t.memberExpression(parentId, prop.key);
 
     if (t.isPattern(pattern2)) {
       push(kind, nodes, pattern2, patternId2);
@@ -41,17 +40,17 @@ var pushArrayPattern = function (kind, nodes, pattern, parentId) {
   _.each(pattern.elements, function (elem, i) {
     if (!elem) return;
 
-    var newPatternId = b.memberExpression(parentId, b.literal(i), true);
+    var newPatternId = t.memberExpression(parentId, t.literal(i), true);
     push(kind, nodes, elem, newPatternId);
   });
 };
 
 var pushPattern = function (kind, nodes, pattern, parentId, file) {
   if (parentId.type !== "MemberExpression" && parentId.type !== "Identifier") {
-    var key = b.identifier(file.generateUid("ref"));
+    var key = t.identifier(file.generateUid("ref"));
 
-    nodes.push(b.variableDeclaration("var", [
-      b.variableDeclarator(key, parentId)
+    nodes.push(t.variableDeclaration("var", [
+      t.variableDeclarator(key, parentId)
     ]));
 
     parentId = key;
@@ -68,9 +67,9 @@ exports.ForOfStatement = function (node, parent, file) {
   var pattern = declar.declarations[0].id;
   if (!t.isPattern(pattern)) return;
 
-  var key = b.identifier(file.generateUid("ref"));
-  node.left = b.variableDeclaration(declar.kind, [
-    b.variableDeclarator(key, null)
+  var key = t.identifier(file.generateUid("ref"));
+  node.left = t.variableDeclaration(declar.kind, [
+    t.variableDeclarator(key, null)
   ]);
 
   var nodes = [];
@@ -92,7 +91,7 @@ exports.Function = function (node, parent, file) {
     if (!t.isPattern(pattern)) return pattern;
 
     hasDestructuring = true;
-    var parentId = b.identifier(file.generateUid("ref"));
+    var parentId = t.identifier(file.generateUid("ref"));
     pushPattern("var", nodes, pattern, parentId, file);
     return parentId;
   });
@@ -113,9 +112,9 @@ exports.ExpressionStatement = function (node, parent, file) {
 
   var nodes = [];
 
-  var ref = b.identifier(file.generateUid("ref"));
-  nodes.push(b.variableDeclaration("var", [
-    b.variableDeclarator(ref, expr.right)
+  var ref = t.identifier(file.generateUid("ref"));
+  nodes.push(t.variableDeclaration("var", [
+    t.variableDeclarator(ref, expr.right)
   ]));
 
   push(false, nodes, expr.left, ref);
@@ -151,7 +150,7 @@ exports.VariableDeclaration = function (node, parent, file) {
     var declar;
 
     _.each(nodes, function (node) {
-      declar = declar || b.variableDeclaration(node.kind, []);
+      declar = declar || t.variableDeclaration(node.kind, []);
 
       if (node.type !== "VariableDeclaration" && declar.kind !== node.kind) {
         throw file.errorWithNode(node, "Cannot use this node within the current parent");
diff --git a/lib/6to5/transformers/for-of.js b/lib/6to5/transformers/for-of.js
index 587a06716b..798b1aa35a 100644
--- a/lib/6to5/transformers/for-of.js
+++ b/lib/6to5/transformers/for-of.js
@@ -1,19 +1,18 @@
 var util = require("../util");
 var t    = require("../types");
-var b    = require("../builders");
 
 exports.ForOfStatement = function (node, parent, file) {
   var left = node.left;
   var declar;
 
-  var stepKey = b.identifier(file.generateUid("step"));
-  var stepValueId = b.memberExpression(stepKey, b.identifier("value"));
+  var stepKey = t.identifier(file.generateUid("step"));
+  var stepValueId = t.memberExpression(stepKey, t.identifier("value"));
 
   if (t.isIdentifier(left)) {
-    declar = b.expressionStatement(b.assignmentExpression("=", left, stepValueId));
+    declar = t.expressionStatement(t.assignmentExpression("=", left, stepValueId));
   } else if (t.isVariableDeclaration(left)) {
-    declar = b.variableDeclaration(left.kind, [
-      b.variableDeclarator(left.declarations[0].id, stepValueId)
+    declar = t.variableDeclaration(left.kind, [
+      t.variableDeclarator(left.declarations[0].id, stepValueId)
     ]);
   } else {
     return;
diff --git a/lib/6to5/transformers/jsx.js b/lib/6to5/transformers/jsx.js
index d4510b03be..bab915a59b 100644
--- a/lib/6to5/transformers/jsx.js
+++ b/lib/6to5/transformers/jsx.js
@@ -2,7 +2,6 @@
 // https://github.com/RReverser/jsx-transpiler
 
 var esutils = require("esutils");
-var b       = require("../builders");
 var t       = require("../types");
 var _       = require("lodash");
 
@@ -18,8 +17,8 @@ exports.Program = function (node, parent, file) {
   });
 
   // prebuilding AST node
-  file.jsx = jsx.split(".").map(b.identifier).reduce(function (object, property) {
-    return b.memberExpression(object, property);
+  file.jsx = jsx.split(".").map(t.identifier).reduce(function (object, property) {
+    return t.memberExpression(object, property);
   });
 };
 
@@ -27,7 +26,7 @@ exports.XJSIdentifier = function (node) {
   if (esutils.keyword.isIdentifierName(node.name)) {
     node.type = "Identifier";
   } else {
-    return b.literal(node.name);
+    return t.literal(node.name);
   }
 };
 
@@ -42,19 +41,14 @@ exports.XJSMemberExpression = {
   }
 };
 
-exports.XJSEmptyExpression = function (node) {
-  node.value = null;
-  node.type = "Literal";
-};
-
 exports.XJSExpressionContainer = function (node) {
   return node.expression;
 };
 
 exports.XJSAttribute = {
   exit: function (node) {
-    var value = node.value || b.literal(true);
-    var propNode = b.property("init", node.name, value);
+    var value = node.value || t.literal(true);
+    var propNode = t.property("init", node.name, value);
     t.inherits(propNode, node);
     return propNode;
   }
@@ -68,18 +62,18 @@ exports.XJSOpeningElement = {
       var tagName = tagExpr.name;
 
       if (/[a-z]/.exec(tagName[0]) || _.contains(tagName, "-")) {
-        tagExpr = b.memberExpression(file.jsx, tagExpr);
+        tagExpr = t.memberExpression(file.jsx, tagExpr);
       }
     }
 
     var props = node.attributes;
     if (props.length) {
-      props = b.objectExpression(props);
+      props = t.objectExpression(props);
     } else {
-      props = b.literal(null);
+      props = t.literal(null);
     }
 
-    return b.callExpression(tagExpr, [props]);
+    return t.callExpression(tagExpr, [props]);
   }
 };
 
diff --git a/lib/6to5/transformers/let-scoping.js b/lib/6to5/transformers/let-scoping.js
index 157e46abf7..7859ce708b 100644
--- a/lib/6to5/transformers/let-scoping.js
+++ b/lib/6to5/transformers/let-scoping.js
@@ -1,7 +1,6 @@
 var traverse = require("../traverse");
 var util     = require("../util");
 var t        = require("../types");
-var b        = require("../builders");
 var _        = require("lodash");
 
 exports.VariableDeclaration = function (node, parent, file) {
@@ -12,7 +11,7 @@ exports.VariableDeclaration = function (node, parent, file) {
 
   _.each(node.declarations, function (declar) {
     _.each(util.getIds(declar.id), function (id) {
-      ids[id] = b.identifier(file.generateUid(id));
+      ids[id] = t.identifier(file.generateUid(id));
     });
   });
 
@@ -43,11 +42,11 @@ exports.VariableDeclaration = function (node, parent, file) {
         if (t.isFunctionDeclaration(node)) {
           throw new Error("`FunctionDeclaration`s that use `let` and `constant` references aren't allowed outside of the root scope");
         } else {
-          var func = b.functionExpression(null, letReferences, b.blockStatement([
-            b.returnStatement(node)
+          var func = t.functionExpression(null, letReferences, t.blockStatement([
+            t.returnStatement(node)
           ]));
           func._aliasFunction = true;
-          return b.callExpression(func, letReferences);
+          return t.callExpression(func, letReferences);
         }
       } else {
         return false;
diff --git a/lib/6to5/transformers/react.js b/lib/6to5/transformers/react.js
index f98b0cc28d..95adf957ff 100644
--- a/lib/6to5/transformers/react.js
+++ b/lib/6to5/transformers/react.js
@@ -1,4 +1,3 @@
-var b = require("../builders");
 var t = require("../types");
 var _ = require("lodash");
 
@@ -34,7 +33,7 @@ var addDisplayName = function (id, call) {
   });
 
   if (safe) {
-    props.unshift(b.property("init", b.identifier("displayName"), b.literal(id)));
+    props.unshift(t.property("init", t.identifier("displayName"), t.literal(id)));
   }
 };
 
diff --git a/lib/6to5/transformers/rest-parameters.js b/lib/6to5/transformers/rest-parameters.js
index 7f020a79f0..c77055f010 100644
--- a/lib/6to5/transformers/rest-parameters.js
+++ b/lib/6to5/transformers/rest-parameters.js
@@ -1,6 +1,5 @@
 var util = require("../util");
 var t    = require("../types");
-var b    = require("../builders");
 
 exports.Function = function (node, parent, file) {
   if (!node.rest) return;
@@ -16,7 +15,7 @@ exports.Function = function (node, parent, file) {
   var template = util.template(templateName, {
     SLICE_KEY: file.addDeclaration("slice"),
     VARIABLE_NAME: rest,
-    SLICE_ARG: b.literal(node.params.length)
+    SLICE_ARG: t.literal(node.params.length)
   });
 
   template.declarations[0].init.arguments[0]._ignoreAliasFunctions = true;
diff --git a/lib/6to5/transformers/spread.js b/lib/6to5/transformers/spread.js
index 01100cb48b..3fefe8c7fb 100644
--- a/lib/6to5/transformers/spread.js
+++ b/lib/6to5/transformers/spread.js
@@ -1,5 +1,4 @@
 var util = require("../util");
-var b    = require("../builders");
 var t    = require("../types");
 var _    = require("lodash");
 
@@ -32,7 +31,7 @@ var build = function (props, file) {
 
   var push = function () {
     if (!_props.length) return;
-    nodes.push(b.arrayExpression(_props));
+    nodes.push(t.arrayExpression(_props));
     _props = [];
   };
 
@@ -59,14 +58,14 @@ exports.ArrayExpression = function (node, parent, file) {
 
   if (!nodes.length) return first;
 
-  return b.callExpression(b.memberExpression(first, b.identifier("concat")), nodes);
+  return t.callExpression(t.memberExpression(first, t.identifier("concat")), nodes);
 };
 
 exports.CallExpression = function (node, parent, file) {
   var args = node.arguments;
   if (!hasSpread(args)) return;
 
-  var contextLiteral = b.literal(null);
+  var contextLiteral = t.literal(null);
 
   node.arguments = [];
 
@@ -74,7 +73,7 @@ exports.CallExpression = function (node, parent, file) {
   var first = nodes.shift();
 
   if (nodes.length) {
-    node.arguments.push(b.callExpression(b.memberExpression(first, b.identifier("concat")), nodes));
+    node.arguments.push(t.callExpression(t.memberExpression(first, t.identifier("concat")), nodes));
   } else {
     node.arguments.push(first);
   }
@@ -85,14 +84,14 @@ exports.CallExpression = function (node, parent, file) {
     contextLiteral = callee.object;
 
     if (callee.computed) {
-      callee.object = b.memberExpression(callee.object, callee.property, true);
-      callee.property = b.identifier("apply");
+      callee.object = t.memberExpression(callee.object, callee.property, true);
+      callee.property = t.identifier("apply");
       callee.computed = false;
     } else {
-      callee.property = b.memberExpression(callee.property, b.identifier("apply"));
+      callee.property = t.memberExpression(callee.property, t.identifier("apply"));
     }
   } else {
-    node.callee = b.memberExpression(node.callee, b.identifier("apply"));
+    node.callee = t.memberExpression(node.callee, t.identifier("apply"));
   }
 
   node.arguments.unshift(contextLiteral);
diff --git a/lib/6to5/transformers/template-literals.js b/lib/6to5/transformers/template-literals.js
index 869a42ed64..69393bed11 100644
--- a/lib/6to5/transformers/template-literals.js
+++ b/lib/6to5/transformers/template-literals.js
@@ -1,9 +1,8 @@
 var t = require("../types");
-var b = require("../builders");
 var _ = require("lodash");
 
 var buildBinaryExpression = function (left, right) {
-  return b.binaryExpression("+", left, right);
+  return t.binaryExpression("+", left, right);
 };
 
 exports.TaggedTemplateExpression = function (node) {
@@ -11,22 +10,22 @@ exports.TaggedTemplateExpression = function (node) {
   var quasi = node.quasi;
 
   var strings = quasi.quasis.map(function (elem) {
-    return b.literal(elem.value.raw);
+    return t.literal(elem.value.raw);
   });
-  args.push(b.arrayExpression(strings));
+  args.push(t.arrayExpression(strings));
 
   _.each(quasi.expressions, function (expr) {
     args.push(expr);
   });
 
-  return b.callExpression(node.tag, args);
+  return t.callExpression(node.tag, args);
 };
 
 exports.TemplateLiteral = function (node) {
   var nodes = [];
 
   _.each(node.quasis, function (elem) {
-    nodes.push(b.literal(elem.value.raw));
+    nodes.push(t.literal(elem.value.raw));
 
     var expr = node.expressions.shift();
     if (expr) nodes.push(expr);
diff --git a/lib/6to5/transformers/use-strict.js b/lib/6to5/transformers/use-strict.js
index c116c0990c..39ca63eff5 100644
--- a/lib/6to5/transformers/use-strict.js
+++ b/lib/6to5/transformers/use-strict.js
@@ -1,4 +1,4 @@
-var b = require("../builders");
+var t = require("../types");
 
 module.exports = function (ast) {
   var body = ast.program.body;
@@ -7,6 +7,6 @@ module.exports = function (ast) {
   var noStrict = !first || first.type !== "ExpressionStatement" || first.expression.type !== "Literal" || first.expression.value !== "use strict";
 
   if (noStrict) {
-    body.unshift(b.expressionStatement(b.literal("use strict")));
+    body.unshift(t.expressionStatement(t.literal("use strict")));
   }
 };
diff --git a/lib/6to5/types/alias-keys.json b/lib/6to5/types/alias-keys.json
new file mode 100644
index 0000000000..9917eb42d1
--- /dev/null
+++ b/lib/6to5/types/alias-keys.json
@@ -0,0 +1,22 @@
+{
+  "ArrowFunctionExpression": ["Function"],
+  "FunctionDeclaration":     ["Function"],
+  "FunctionExpression":      ["Function"],
+
+  "LogicalExpression": ["Binary"],
+  "BinaryExpression":  ["Binary"],
+
+  "UnaryExpression": ["UnaryLike"],
+  "SpreadProperty":  ["UnaryLike"],
+  "SpreadElement":   ["UnaryLike"],
+
+  "ClassDeclaration": ["Class"],
+  "ClassExpression":  ["Class"],
+
+  "ForOfStatement": ["For"],
+  "ForInStatement": ["For"],
+  "ForStatement":   ["For"],
+
+  "ObjectPattern": ["Pattern"],
+  "ArrayPattern":  ["Pattern"]
+}
diff --git a/lib/6to5/types/builder-keys.json b/lib/6to5/types/builder-keys.json
new file mode 100644
index 0000000000..c7f0695560
--- /dev/null
+++ b/lib/6to5/types/builder-keys.json
@@ -0,0 +1,18 @@
+{
+  "ArrayExpression":      ["elements"],
+  "AssignmentExpression": ["operator", "left", "right"],
+  "BinaryExpression":     ["operator", "left", "right"],
+  "BlockStatement":       ["body"],
+  "CallExpression":       ["callee", "arguments"],
+  "ExpressionStatement":  ["expression"],
+  "FunctionExpression":   ["id", "params", "body"],
+  "Identifier":           ["name"],
+  "IfStatement":          ["test", "consequent", "alternate"],
+  "Literal":              ["value"],
+  "MemberExpression":     ["object", "property", "computed"],
+  "ObjectExpression":     ["properties"],
+  "Property":             ["kind", "key", "value"],
+  "ReturnStatement":      ["argument"],
+  "VariableDeclaration":  ["kind", "declarations"],
+  "VariableDeclarator":   ["id", "init"]
+}
diff --git a/lib/6to5/types.js b/lib/6to5/types/index.js
similarity index 82%
rename from lib/6to5/types.js
rename to lib/6to5/types/index.js
index f42d6d9159..cc071629c1 100644
--- a/lib/6to5/types.js
+++ b/lib/6to5/types/index.js
@@ -1,5 +1,4 @@
-var traverse = require("./traverse");
-var b        = require("./builders");
+var traverse = require("../traverse");
 var n        = require("acorn-ast-types").namedTypes;
 var _        = require("lodash");
 
@@ -13,30 +12,41 @@ _.each(traverse.VISITOR_KEYS, function (keys, type) {
   };
 });
 
-var buildIs = function (isKey, typeKey, types) {
-  t[typeKey + "_TYPES"] = types;
+//
 
-  t["is" + isKey] = function (node) {
-    return node && _.contains(types, node.type);
+t.BUILDER_KEYS = _.defaults(require("./builder-keys"), traverse.VISITOR_KEYS);
+
+_.each(t.BUILDER_KEYS, function (keys, type) {
+  t[type[0].toLowerCase() + type.slice(1)] = function () {
+    var args = arguments;
+    var node = { type: type };
+    _.each(keys, function (key, i) {
+      node[key] = args[i];
+    });
+    return node;
   };
-};
-
-buildIs("Function", "FUNCTION", ["ArrowFunctionExpression", "FunctionDeclaration", "FunctionExpression"]);
-buildIs("Class", "CLASS", ["ClassDeclaration", "ClassExpression"]);
-buildIs("Pattern", "PATTERN", ["ArrayPattern", "ObjectPattern"]);
-buildIs("Binary", "BINARY", ["BinaryExpression", "LogicalExpression"]);
-buildIs("UnaryLike", "UNARY", ["UnaryExpression", "SpreadElement", "SpreadProperty"]);
+});
 
 //
 
-t.aliases = {
-  ArrowFunctionExpression: ["Function"],
-  FunctionDeclaration:     ["Function"],
-  FunctionExpression:      ["Function"],
+t.ALIAS_KEYS = require("./alias-keys");
 
-  ClassDeclaration: ["Class"],
-  ClassExpression:  ["Class"]
-};
+var _aliases = {};
+
+_.each(t.ALIAS_KEYS, function (aliases, type) {
+  _.each(aliases, function (alias) {
+    var types = _aliases[alias] = _aliases[alias] || [];
+    types.push(type);
+  });
+});
+
+_.each(_aliases, function (types, type) {
+  t[type.toUpperCase() + "_TYPES"] = types;
+
+  t["is" + type] = function (node) {
+    return node && _.contains(types, node.type);
+  };
+});
 
 //
 
@@ -70,16 +80,16 @@ t.toBlock = function (node, parent) {
   if (!_.isArray(node)) {
     if (!n.Statement.check(node)) {
       if (t.isFunction(parent)) {
-        node = b.returnStatement(node);
+        node = t.returnStatement(node);
       } else {
-        node = b.expressionStatement(node);
+        node = t.expressionStatement(node);
       }
     }
 
     node = [node];
   }
 
-  return b.blockStatement(node);
+  return t.blockStatement(node);
 };
 
 t.inherits = function (child, parent) {
@@ -101,7 +111,11 @@ t.needsWhitespace = function (node, expression) {
 
   //
 
-  if (t.isFunction(node) || t.isClass(node)) {
+  if (t.isFunction(node) || t.isClass(node) || t.isFor(node) || t.isSwitchStatement(node)) {
+    return true;
+  }
+
+  if (t.isIfStatement(node) && t.isBlockStatement(node.consequent)) {
     return true;
   }
 
@@ -128,6 +142,10 @@ t.needsWhitespace = function (node, expression) {
     exprs = node.elements;
   }
 
+  if (t.isObjectExpression(node)) {
+    exprs = node.properties;
+  }
+
   return exprs.some(function (expr) {
     return t.needsWhitespace(expr, true);
   });
diff --git a/lib/6to5/util.js b/lib/6to5/util.js
index 5e1eb5ebac..af2b740605 100644
--- a/lib/6to5/util.js
+++ b/lib/6to5/util.js
@@ -5,7 +5,6 @@ var path       = require("path");
 var util       = require("util");
 var fs         = require("fs");
 var t          = require("./types");
-var b          = require("./builders");
 var _          = require("lodash");
 
 _.extend(estraverse.VisitorKeys, traverse.VISITOR_KEYS);
@@ -37,7 +36,7 @@ exports.getUid = function (parent, file) {
 
   if (t.isIdentifier(node)) id = node.name;
 
-  return b.identifier(file.generateUid(id));
+  return t.identifier(file.generateUid(id));
 };
 
 exports.isAbsolute = function (loc) {
@@ -100,17 +99,17 @@ exports.pushMutatorMap = function (mutatorMap, key, kind, method) {
 };
 
 exports.buildDefineProperties = function (mutatorMap) {
-  var objExpr = b.objectExpression([]);
+  var objExpr = t.objectExpression([]);
 
   _.each(mutatorMap, function (map, key) {
-    var mapNode = b.objectExpression([]);
+    var mapNode = t.objectExpression([]);
 
-    var propNode = b.property("init", b.identifier(key), mapNode);
+    var propNode = t.property("init", t.identifier(key), mapNode);
 
     _.each(map, function (node, key) {
       node = _.clone(node);
       if (t.isMethodDefinition(node)) node = node.value;
-      mapNode.properties.push(b.property("init", b.identifier(key), node));
+      mapNode.properties.push(t.property("init", t.identifier(key), node));
     });
 
     objExpr.properties.push(propNode);
@@ -250,7 +249,7 @@ try {
   if (!fs.existsSync(templatesLoc)) {
     throw new Error("no templates directory - this is most likely the result" +
                     " of a broken `npm publish`. Please report to " +
-                    "https://github.com/sebmck/6to5/issues");
+                    "https://githut.com/sebmck/6to5/issues");
   }
 
   _.each(fs.readdirSync(templatesLoc), function (name) {