break up let scoping

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

@@ -143,24 +143,25 @@ var checkFor = function (forParent, block) {
   return has;
 };
 
-var run = function (forParent, block, parent, file, scope) {
-  if (block._letDone) return;
-  block._letDone = true;
+var hoistVarDeclarations = function (block, pushDeclar) {
+  traverse(block, function (node) {
+    if (t.isForStatement(node)) {
+      if (isVar(node.init)) {
+        node.init = t.sequenceExpression(pushDeclar(node.init));
+      }
+    } else if (t.isFor(node)) {
+      if (isVar(node.left)) {
+        node.left = node.left.declarations[0].id;
+      }
+    } else if (isVar(node)) {
+      return pushDeclar(node).map(t.expressionStatement);
+    } else if (t.isFunction(node)) {
+      return false;
+    }
+  });
+};
 
-  var info = getInfo(block, file, scope);
-  var declarators = info.declarators;
-  var letKeys = info.keys;
-
-  // this is a block within a `Function` so we can safely leave it be
-  if (t.isFunction(parent)) return;
-
-  // this block has no let references so let's clean up
-  if (!letKeys.length) return noClosure(declarators, block, info.duplicates);
-
-  // outside let references that we need to wrap
-  var letReferences = {};
-
-  // are there any outside let references within any functions?
+var getLetReferences = function (info, block, letReferences) {
   var closurify = false;
 
   // traverse through this block, stopping on functions and checking if they
@@ -193,6 +194,30 @@ var run = function (forParent, block, parent, file, scope) {
     }
   });
 
+  return closurify;
+};
+
+var run = function (forParent, block, parent, file, scope) {
+  if (block._letDone) return;
+  block._letDone = true;
+
+  var info = getInfo(block, file, scope);
+  var declarators = info.declarators;
+  var letKeys = info.keys;
+
+  // this is a block within a `Function` so we can safely leave it be
+  if (t.isFunction(parent)) return;
+
+  // this block has no let references so let's clean up
+  if (!letKeys.length) return noClosure(declarators, block, info.duplicates);
+
+  // outside let references that we need to wrap
+  var letReferences = {};
+
+  // returns whether or not there are any outside let references within any
+  // functions
+  var closurify = getLetReferences(info, block, letReferences);
+
   letReferences = _.values(letReferences);
 
   // no need for a closure so let's clean up
@@ -223,21 +248,7 @@ var run = function (forParent, block, parent, file, scope) {
   };
 
   // hoist var references to retain scope
-  traverse(block, function (node) {
-    if (t.isForStatement(node)) {
-      if (isVar(node.init)) {
-        node.init = t.sequenceExpression(pushDeclar(node.init));
-      }
-    } else if (t.isFor(node)) {
-      if (isVar(node.left)) {
-        node.left = node.left.declarations[0].id;
-      }
-    } else if (isVar(node)) {
-      return pushDeclar(node).map(t.expressionStatement);
-    } else if (t.isFunction(node)) {
-      return false;
-    }
-  });
+  hoistVarDeclarations(block, pushDeclar);
 
   // set let references to plain var references
   standardiseLets(declarators);
@@ -299,7 +310,6 @@ var run = function (forParent, block, parent, file, scope) {
 
       body.push(t.switchStatement(ret, cases));
     }
-
   } else {
     body.push(t.expressionStatement(call));
   }