add isBlockedScoped types helper

lib/6to5/traverse/scope.js

@@ -135,7 +135,7 @@ Scope.prototype.getInfo = function () {
   if (t.isFor(block)) {
     _.each(FOR_KEYS, function (key) {
       var node = block[key];
-      if (t.isLet(node)) add(node);
+      if (t.isBlockScoped(node)) add(node);
     });
   }
 
@@ -144,7 +144,7 @@ Scope.prototype.getInfo = function () {
   if (t.isBlockStatement(block) || t.isProgram(block)) {
     _.each(block.body, function (node) {
       // check for non-var `VariableDeclaration`s
-      if (t.isLet(node)) add(node);
+      if (t.isBlockScoped(node)) add(node);
     });
   }
 
@@ -190,7 +190,7 @@ Scope.prototype.getInfo = function () {
 
         // we've ran into a declaration!
         // we'll let the BlockStatement scope deal with `let` declarations unless
-        if (t.isDeclaration(node) && !t.isLet(node)) {
+        if (t.isDeclaration(node) && !t.isBlockScoped(node)) {
           state.add(node);
         }
       }

lib/6to5/types/index.js

@@ -497,6 +497,17 @@ t.isLet = function (node) {
   return t.isVariableDeclaration(node) && (node.kind !== "var" || node._let);
 };
 
+/**
+ * Description
+ *
+ * @param {Object} node
+ * @returns {Boolean}
+ */
+
+t.isBlockScoped = function (node) {
+  return t.isFunctionDeclaration(node) || t.isLet(node);
+};
+
 /**
  * Description
  *