Fix implicit returns of assignments

commit e5c5af2ba97c0068d52901f3a6dc30b5017181fa
Author: William C. Johnson <wcjohnson@oigroup.net>
Date:   Sat May 13 15:17:37 2017 -0400

    Fix implicit returns of assignments

Author: wcjohnson

src/index.js

@@ -195,12 +195,7 @@ export default function (babel) {
       if (!tailPath) continue;
 
       if (tailPath.isExpressionStatement()) {
-        // TODO: add linting to discourage
-        if (tailPath.get("expression").isAssignmentExpression()) {
-          tailPath.insertAfter(getNewNode(tailPath.node.expression.left, tailPath));
-        } else {
-          tailPath.replaceWith(getNewNode(tailPath.node.expression, tailPath));
-        }
+        tailPath.replaceWith(getNewNode(tailPath.node.expression, tailPath));
       } else if (tailPath.isVariableDeclaration()) {
         // TODO: handle declarations.length > 1
         // TODO: add linting to discourage

test/fixtures/await-arrow/assign-member/expected.js

@@ -1,4 +1,3 @@
 async function fn() {
-  x.y = await fetch();
-  return x.y;
-}
+  return x.y = await fetch();
+}

test/fixtures/comprehensions/assignment-expr/exec.js

@@ -0,0 +1,6 @@
+let x = 0
+result = [for idx i in Array(10):
+  now x = i
+]
+assert.deepEqual(result, [0,1,2,3,4,5,6,7,8,9])
+assert(x === 9)

test/fixtures/comprehensions/assignment-expr/expected.js

@@ -2,9 +2,7 @@
   const _arr = [];
 
   for (let _arr2 = Array(10), i = 0, _len = _arr2.length; i < _len; i++) {
-    x = f(i);
-
-    _arr.push(x)
+    _arr.push(x = f(i));
   }
 
   return _arr;

test/fixtures/implicit-returns/assign/expected.js

@@ -1,4 +1,3 @@
 function fn(x) {
-  x = 4;
-  return x;
-}
+  return x = 4;
+}

test/fixtures/implicit-returns/member-assign/expected.js

@@ -1,4 +1,3 @@
 function fn(obj) {
-  obj.x = 4;
-  return obj.x;
-}
+  return obj.x = 4;
+}