Proof of concept of how traversal would look like with state parameter

lib/6to5/transformation/helpers/name-method.js

@@ -2,6 +2,24 @@ var traverse = require("../../traverse");
 var util     = require("../../util");
 var t        = require("../../types");
 
+var traverser = {
+  enter: function (node, parent, scope, context, state) {
+    // check if this node is an identifier that matches the same as our function id
+    if (!t.isIdentifier(node, { name: state.id })) return;
+
+    // check if this node is the one referenced
+    if (!t.isReferenced(node, parent)) return;
+
+    // check that we don't have a local variable declared as that removes the need
+    // for the wrapper
+    var localDeclar = scope.get(state.id, true);
+    if (localDeclar !== state.outerDeclar) return;
+
+    state.selfReference = true;
+    context.stop();
+  }
+};
+
 module.exports = function (node, file, scope) {
   var key = t.toComputedKey(node, node.key);
   if (!t.isLiteral(key)) return node; // we can't set a function id with this
@@ -15,23 +33,7 @@ module.exports = function (node, file, scope) {
     outerDeclar: scope.get(id, true),
   };
 
-  traverse(node, {
+  traverse(node, traverser, scope, state);
-    enter: function (node, parent, scope, context, state) {
-      // check if this node is an identifier that matches the same as our function id
-      if (!t.isIdentifier(node, { name: state.id })) return;
-
-      // check if this node is the one referenced
-      if (!t.isReferenced(node, parent)) return;
-
-      // check that we don't have a local variable declared as that removes the need
-      // for the wrapper
-      var localDeclar = scope.get(state.id, true);
-      if (localDeclar !== state.outerDeclar) return;
-
-      state.selfReference = true;
-      context.stop();
-    }
-  }, scope, state);
 
   if (state.selfReference) {
     node.value = util.template("property-method-assignment-wrapper", {

lib/6to5/transformation/modules/_default.js

@@ -16,35 +16,51 @@ function DefaultFormatter(file) {
   //this.checkCollisions();
 }
 
+var exportsTraverser = {
+  enter: function (node, parent, scope, context, localExports) {
+    var declar = node && node.declaration;
+    if (t.isExportDeclaration(node) && declar && t.isStatement(declar)) {
+      _.extend(localExports, t.getIds(declar, true));
+    }
+  }
+};
+
 DefaultFormatter.prototype.getLocalExports = function () {
   var localExports = {};
-
+  traverse(this.file.ast, exportsTraverser, null, localExports);
-  traverse(this.file.ast, {
-    enter: function (node, parent, scope, context, localExports) {
-      var declar = node && node.declaration;
-      if (t.isExportDeclaration(node) && declar && t.isStatement(declar)) {
-        _.extend(localExports, t.getIds(declar, true));
-      }
-    }
-  }, null, localExports);
-
   return localExports;
 };
 
+var importsTraverser = {
+  enter: function (node, parent, scope, context, localImports) {
+    if (t.isImportDeclaration(node)) {
+      _.extend(localImports, t.getIds(node, true));
+    }
+  }
+};
+
 DefaultFormatter.prototype.getLocalImports = function () {
   var localImports = {};
-
+  traverse(this.file.ast, importsTraverser, null, localImports);
-  traverse(this.file.ast, {
-    enter: function (node, parent, scope, context, localImports) {
-      if (t.isImportDeclaration(node)) {
-        _.extend(localImports, t.getIds(node, true));
-      }
-    }
-  }, null, localImports);
-
   return localImports;
 };
 
+var collissionsTraverser = {
+  enter: function (node, parent, scope, context, check) {
+    if (t.isAssignmentExpression(node)) {
+
+      var left = node.left;
+      if (t.isMemberExpression(left)) {
+        while (left.object) left = left.object;
+      }
+
+      check(left);
+    } else if (t.isDeclaration(node)) {
+      _.each(t.getIds(node, true), check);
+    }
+  }
+};
+
 DefaultFormatter.prototype.checkCollisions = function () {
   // todo: all check export collissions
 
@@ -61,21 +77,7 @@ DefaultFormatter.prototype.checkCollisions = function () {
     }
   };
 
-  traverse(file.ast, {
+  traverse(file.ast, collissionsTraverser, null, check);
-    enter: function (node, parent, scope, context, check) {
-      if (t.isAssignmentExpression(node)) {
-
-        var left = node.left;
-        if (t.isMemberExpression(left)) {
-          while (left.object) left = left.object;
-        }
-
-        check(left);
-      } else if (t.isDeclaration(node)) {
-        _.each(t.getIds(node, true), check);
-      }
-    }
-  }, null, check);
 };
 
 DefaultFormatter.prototype.remapExportAssignment = function (node) {

lib/6to5/transformation/transformers/_alias-functions.js

@@ -1,6 +1,46 @@
 var traverse = require("../../traverse");
 var t        = require("../../types");
 
+var functionChildrenTraverser = {
+  enter: function (node, parent, scope, context, state) {
+    if (t.isFunction(node) && !node._aliasFunction) {
+      return context.skip();
+    }
+
+    if (node._ignoreAliasFunctions) return context.skip();
+
+    var getId;
+
+    if (t.isIdentifier(node) && node.name === "arguments") {
+      getId = state.getArgumentsId;
+    } else if (t.isThisExpression(node)) {
+      getId = state.getThisId;
+    } else {
+      return;
+    }
+
+    if (t.isReferenced(node, parent)) return getId();
+  }
+};
+
+var functionTraverser = {
+  enter: function (node, parent, scope, context, state) {
+    if (!node._aliasFunction) {
+      if (t.isFunction(node)) {
+        // stop traversal of this node as it'll be hit again by this transformer
+        return context.skip();
+      } else {
+        return;
+      }
+    }
+
+    // traverse all child nodes of this function and find `arguments` and `this`
+    traverse(node, functionChildrenTraverser, null, state);
+
+    return context.skip();
+  }
+};
+
 var go = function (getBody, node, file, scope) {
   var argumentsId;
   var thisId;
@@ -16,43 +56,7 @@ var go = function (getBody, node, file, scope) {
 
   // traverse the function and find all alias functions so we can alias
   // `arguments` and `this` if necessary
-  traverse(node, {
+  traverse(node, functionTraverser, null, state);
-    enter: function (node, parent, scope, context, state) {
-      if (!node._aliasFunction) {
-        if (t.isFunction(node)) {
-          // stop traversal of this node as it'll be hit again by this transformer
-          return context.skip();
-        } else {
-          return;
-        }
-      }
-
-      // traverse all child nodes of this function and find `arguments` and `this`
-      traverse(node, {
-        enter: function (node, parent, scope, context, state) {
-          if (t.isFunction(node) && !node._aliasFunction) {
-            return context.skip();
-          }
-
-          if (node._ignoreAliasFunctions) return context.skip();
-
-          var getId;
-
-          if (t.isIdentifier(node) && node.name === "arguments") {
-            getId = state.getArgumentsId;
-          } else if (t.isThisExpression(node)) {
-            getId = state.getThisId;
-          } else {
-            return;
-          }
-
-          if (t.isReferenced(node, parent)) return getId();
-        }
-      }, null, state);
-
-      return context.skip();
-    }
-  }, null, state);
 
   var body;
 

lib/6to5/util.js

@@ -129,6 +129,14 @@ exports.buildDefineProperties = function (mutatorMap) {
   return objExpr;
 };
 
+var templateTraverser = {
+  enter: function (node, parent, scope, context, nodes) {
+    if (t.isIdentifier(node) && _.has(nodes, node.name)) {
+      return nodes[node.name];
+    }
+  }
+};
+
 exports.template = function (name, nodes, keepExpression) {
   var template = exports.templates[name];
   if (!template) throw new ReferenceError("unknown template " + name);
@@ -141,13 +149,7 @@ exports.template = function (name, nodes, keepExpression) {
   template = _.cloneDeep(template);
 
   if (!_.isEmpty(nodes)) {
-    traverse(template, {
+    traverse(template, templateTraverser, null, nodes);
-      enter: function (node, parent, scope, context, nodes) {
-        if (t.isIdentifier(node) && _.has(nodes, node.name)) {
-          return nodes[node.name];
-        }
-      }
-    }, null, nodes);
   }
 
   var node = template.body[0];