use isConsequenceExpressionStatement to correctly evaluate expressions - fixes #502

lib/6to5/transformation/helpers/build-binary-assignment-operator-transformer.js

@@ -13,6 +13,9 @@ module.exports = function (exports, opts) {
   };
 
   exports.ExpressionStatement = function (node, parent, scope, context, file) {
+    // hit the `AssignmentExpression` one below
+    if (file.isConsequenceExpressionStatement(node)) return;
+
     var expr = node.expression;
     if (!isAssignment(expr)) return;
 
@@ -27,13 +30,11 @@ module.exports = function (exports, opts) {
   };
 
   exports.AssignmentExpression = function (node, parent, scope, context, file) {
-    if (t.isExpressionStatement(parent)) return;
     if (!isAssignment(node)) return;
 
     var nodes    = [];
     var exploded = explode(node.left, nodes, file, scope);
-    nodes.push(opts.build(exploded.uid, node.right));
-    nodes.push(exploded.ref);
+    nodes.push(buildAssignment(exploded.ref, opts.build(exploded.uid, node.right)));
 
     return t.toSequenceExpression(nodes, scope);
   };

lib/6to5/transformation/helpers/build-conditional-assignment-operator-transformer.js

@@ -9,6 +9,9 @@ module.exports = function (exports, opts) {
   };
 
   exports.ExpressionStatement = function (node, parent, scope, context, file) {
+    // hit the `AssignmentExpression` one below
+    if (file.isConsequenceExpressionStatement(node)) return;
+
     var expr = node.expression;
     if (!opts.is(expr, file)) return;
 
@@ -25,7 +28,6 @@ module.exports = function (exports, opts) {
   };
 
   exports.AssignmentExpression = function (node, parent, scope, context, file) {
-    if (t.isExpressionStatement(parent)) return;
     if (!opts.is(node, file)) return;
 
     var nodes    = [];

lib/6to5/transformation/transformers/es6/destructuring.js

@@ -236,6 +236,7 @@ exports.CatchClause = function (node, parent, scope, context, file) {
 exports.ExpressionStatement = function (node, parent, scope, context, file) {
   var expr = node.expression;
   if (expr.type !== "AssignmentExpression") return;
+  if (file.isConsequenceExpressionStatement(node)) return;
 
   if (!t.isPattern(expr.left)) return;
 
@@ -256,7 +257,6 @@ exports.ExpressionStatement = function (node, parent, scope, context, file) {
 };
 
 exports.AssignmentExpression = function (node, parent, scope, context, file) {
-  if (parent.type === "ExpressionStatement") return;
   if (!t.isPattern(node.left)) return;
 
   var ref = scope.generateUidIdentifier("temp");

lib/6to5/transformation/transformers/es7/abstract-references.js

@@ -7,8 +7,8 @@ var t    = require("../../../types");
 
 exports.experimental = true;
 
-var container = function (parent, call, ret) {
-  if (t.isExpressionStatement(parent)) {
+var container = function (parent, call, ret, file) {
+  if (t.isExpressionStatement(parent) && !file.isConsequenceExpressionStatement(parent)) {
     // we don't need to worry about return values
     return call;
   } else {
@@ -23,7 +23,7 @@ var container = function (parent, call, ret) {
   }
 };
 
-exports.AssignmentExpression = function (node, parent, scope) {
+exports.AssignmentExpression = function (node, parent, scope, context, file) {
   var left = node.left;
   if (!t.isVirtualPropertyExpression(left)) return;
 
@@ -60,10 +60,10 @@ exports.AssignmentExpression = function (node, parent, scope) {
     ]);
   }
 
-  return container(parent, call, value);
+  return container(parent, call, value, file);
 };
 
-exports.UnaryExpression = function (node, parent) {
+exports.UnaryExpression = function (node, parent, scope, context, file) {
   var arg = node.argument;
   if (!t.isVirtualPropertyExpression(arg)) return;
   if (node.operator !== "delete") return;
@@ -73,7 +73,7 @@ exports.UnaryExpression = function (node, parent) {
     OBJECT:   arg.object
   });
 
-  return container(parent, call, t.literal(true));
+  return container(parent, call, t.literal(true), file);
 };
 
 exports.CallExpression = function (node, parent, scope) {

lib/6to5/transformation/transformers/spec/proto-to-assign.js

@@ -20,7 +20,6 @@ exports.optional = true;
 exports.secondPass = true;
 
 exports.AssignmentExpression = function (node, parent, scope, context, file) {
-  if (t.isExpressionStatement(parent)) return;
   if (!isProtoAssignmentExpression(node)) return;
 
   var nodes = [];

test/fixtures/transformation/es7-exponentian-operator/assignment/actual.js

@@ -1 +1,2 @@
 num **= 2;
+;

test/fixtures/transformation/es7-exponentian-operator/assignment/expected.js

@@ -1,3 +1,4 @@
 "use strict";
 
 num = Math.pow(num, 2);
+;