break up let scoping transformer some more

lib/6to5/transformation/transformers/let-scoping.js

@@ -161,12 +161,20 @@ var hoistVarDeclarations = function (block, pushDeclar) {
   });
 };
 
-var getLetReferences = function (info, block, letReferences) {
+var getParams = function (info, letReferences) {
+  var params = _.cloneDeep(letReferences);
+  _.each(params, function (param) {
+    param.name = info.duplicates[param.name] || param.name;
+  });
+  return params;
+};
+
+var getLetReferences = function (block, info, letReferences) {
   var closurify = false;
 
   // traverse through this block, stopping on functions and checking if they
   // contain any outside let references
-  traverse(block, function (node, parent, opts) {
+  traverse(block, function (node, parent, scope) {
     if (t.isFunction(node)) {
       traverse(node, function (node, parent) {
         // not an identifier so we have no use
@@ -177,7 +185,7 @@ var getLetReferences = function (info, block, letReferences) {
 
         // this scope has a variable with the same name so it couldn't belong
         // to our let scope
-        if (opts.scope.hasOwn(node.name)) return;
+        if (scope.hasOwn(node.name)) return;
 
         closurify = true;
 
@@ -197,6 +205,25 @@ var getLetReferences = function (info, block, letReferences) {
   return closurify;
 };
 
+var buildPushDeclar = function (body) {
+  return function (node) {
+    body.push(t.variableDeclaration(node.kind, node.declarations.map(function (declar) {
+      return t.variableDeclarator(declar.id);
+    })));
+
+    var replace = [];
+
+    _.each(node.declarations, function (declar) {
+      if (!declar.init) return;
+
+      var expr = t.assignmentExpression("=", declar.id, declar.init);
+      replace.push(t.inherits(expr, declar));
+    });
+
+    return replace;
+  };
+};
+
 var run = function (forParent, block, parent, file, scope) {
   if (block._letDone) return;
   block._letDone = true;
@@ -216,7 +243,7 @@ var run = function (forParent, block, parent, file, scope) {
 
   // returns whether or not there are any outside let references within any
   // functions
-  var closurify = getLetReferences(info, block, letReferences);
+  var closurify = getLetReferences(block, info, letReferences);
 
   letReferences = _.values(letReferences);
 
@@ -230,22 +257,7 @@ var run = function (forParent, block, parent, file, scope) {
   var body = [];
 
   // hoist a `VariableDeclaration` and add `AssignmentExpression`s in it's place
-  var pushDeclar = function (node) {
-    body.push(t.variableDeclaration(node.kind, node.declarations.map(function (declar) {
-      return t.variableDeclarator(declar.id);
-    })));
-
-    var replace = [];
-
-    _.each(node.declarations, function (declar) {
-      if (!declar.init) return;
-
-      var expr = t.assignmentExpression("=", declar.id, declar.init);
-      replace.push(t.inherits(expr, declar));
-    });
-
-    return replace;
-  };
+  var pushDeclar = buildPushDeclar(body);
 
   // hoist var references to retain scope
   hoistVarDeclarations(block, pushDeclar);
@@ -260,11 +272,8 @@ var run = function (forParent, block, parent, file, scope) {
   // replace the current block body with the one we've built
   block.body = body;
 
-  // cahnge duplicate let references to their uid if they have one
-  var params = _.cloneDeep(letReferences);
-  _.each(params, function (param) {
-    param.name = info.duplicates[param.name] || param.name;
-  });
+  // change duplicate let references to their uid if they have one
+  var params = getParams(info, letReferences);
 
   var call = t.callExpression(fn, params);
   var ret  = t.identifier(file.generateUid("ret", scope));