Merge pull request #3380 from babel/unary-arrow

Fix: Add parens for unary arrow function

packages/babel-generator/src/node/parentheses.js

@@ -203,6 +203,10 @@ export function ArrowFunctionExpression(node, parent) {
     return true;
   }
 
+  if (t.isUnaryExpression(parent)) {
+    return true;
+  }
+
   return UnaryLike(node, parent);
 }
 

packages/babel-generator/test/fixtures/parentheses/unary-arrow-function/actual.js

@@ -0,0 +1,3 @@
+void (() => {});
+typeof (() => {});
+!(() => {});

packages/babel-generator/test/fixtures/parentheses/unary-arrow-function/expected.js

@@ -0,0 +1,3 @@
+void (() => {});
+typeof (() => {});
+!(() => {});