Fix missing parenthesis for typeof and arrow functions (#249)

src/fast-path.js

@@ -371,11 +371,14 @@ FPp.needsParens = function(assumeExpressionContext) {
         return true;
       }
 
-      if (parent.type === "MemberExpression") {
-        return true;
-      }
+      switch (parent.type) {
+        case "MemberExpression":
+        case "UnaryExpression":
+          return true;
 
-      return isBinary(parent);
+        default:
+          return isBinary(parent);
+      }
 
     case "ClassExpression":
       return parent.type === "ExpressionStatement";

tests/arrows/__snapshots__/jsfmt.spec.js.snap

@@ -27,9 +27,12 @@ var ident = <T>(x: T): T => x;
 
 exports[`test arrow_function_expression.js 1`] = `
 "(a => {}).length
+typeof (() => {});
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 (a => {
 }).length;
+typeof (() => {
+});
 "
 `;
 

tests/arrows/arrow_function_expression.js

@@ -1 +1,2 @@
 (a => {}).length
+typeof (() => {});