fix(typescript): ArrowFunctionExpression needs parens in TSAsExpression (#1541)

src/fast-path.js

@@ -515,6 +515,7 @@ FPp.needsParens = function() {
         case "MemberExpression":
           return name === "object";
 
+        case "TSAsExpression":
         case "BindExpression":
         case "TaggedTemplateExpression":
         case "UnaryExpression":

tests/typescript/conformance/expressions/asOperator/__snapshots__/jsfmt.spec.js.snap

@@ -0,0 +1,10 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`asOperatorContextualType.ts 1`] = `
+// should error
+var x = (v => v) as (x: number) => string;
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+// should error
+var x = (v => v) as (x: number) => string;
+
+`;

tests/typescript/conformance/expressions/asOperator/asOperatorContextualType.ts

@@ -0,0 +1,2 @@
+// should error
+var x = (v => v) as (x: number) => string;

tests/typescript/conformance/expressions/asOperator/jsfmt.spec.js

@@ -0,0 +1 @@
+run_spec(__dirname, { parser: "typescript" });