TypeScript: keep parens around with yield/await non-null assertion, fixes #2137 (#2149)

src/fast-path.js

@@ -385,7 +385,8 @@ FastPath.prototype.needsParens = function(options) {
       if (
         parent.type === "UnaryExpression" ||
         parent.type === "AwaitExpression" ||
-        parent.type === "TSAsExpression"
+        parent.type === "TSAsExpression" ||
+        parent.type === "TSNonNullExpression"
       ) {
         return true;
       }
@@ -398,6 +399,7 @@ FastPath.prototype.needsParens = function(options) {
         case "SpreadElement":
         case "SpreadProperty":
         case "TSAsExpression":
+        case "TSNonNullExpression":
           return true;
 
         case "MemberExpression":

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

@@ -3,8 +3,24 @@
 exports[`parens.ts 1`] = `
 (a ? b : c) ![tokenKey];
 (a || b) ![tokenKey];
+
+async function f() {
+    return (await foo())!;
+}
+
+function* g() {
+    return (yield * foo())!;
+}
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 (a ? b : c)![tokenKey];
 (a || b)![tokenKey];
 
+async function f() {
+  return (await foo())!;
+}
+
+function* g() {
+  return (yield* foo())!;
+}
+
 `;

tests/typescript_non_null/parens.ts

@@ -1,2 +1,10 @@
 (a ? b : c) ![tokenKey];
 (a || b) ![tokenKey];
+
+async function f() {
+    return (await foo())!;
+}
+
+function* g() {
+    return (yield * foo())!;
+}