ensureBlock on if statements with expression return statements - fixes #764

lib/6to5/transformation/transformers/es6/tail-call.js

@@ -294,7 +294,15 @@ TailCallTransformer.prototype.subTransformCallExpression = function (node) {
 // looks for and replaces tail recursion calls
 var firstPass = {
   enter: function (node, parent, scope, state) {
-    if (t.isReturnStatement(node)) {
+    if (t.isIfStatement(node)) {
+      if (t.isReturnStatement(node.alternate)) {
+        t.ensureBlock(node, "alternate");
+      }
+
+      if (t.isReturnStatement(node.consequent)) {
+        t.ensureBlock(node, "consequent");
+      }
+    } else if (t.isReturnStatement(node)) {
       this.skip();
       return state.subTransform(node.argument);
     } else if (t.isTryStatement(parent)) {

test/fixtures/transformation/es6-tail-call/expression-consequent/actual.js

@@ -0,0 +1,4 @@
+function f() {
+  if (true) {}
+  else return f()
+}

test/fixtures/transformation/es6-tail-call/expression-consequent/expected.js

@@ -0,0 +1,9 @@
+"use strict";
+
+function f() {
+  _function: while (true) {
+    if (true) {} else {
+      continue _function;
+    }
+  }
+}