Yield expression parens (#16194)

Co-authored-by: fisker Cheung <lionkay@gmail.com>

changelog_unreleased/typescript/16194.md

@@ -0,0 +1,21 @@
+#### Add necessary parentheses to yield expressions (#16194 by @kirkwaiblinger)
+
+Add parentheses around yield expressions if parent is an angle-bracket type assertion.
+
+<!-- prettier-ignore -->
+```ts
+// Input
+function* g() {
+  const y = <T>(yield x);
+}
+
+// Prettier stable
+function* g() {
+  const y = <T>yield x;
+}
+
+// Prettier main
+function* g() {
+  const y = <T>(yield x);
+}
+```

src/language-js/needs-parens.js

@@ -472,7 +472,10 @@ function needsParens(path, options) {
       }
 
     case "YieldExpression":
-      if (parent.type === "AwaitExpression") {
+      if (
+        parent.type === "AwaitExpression" ||
+        parent.type === "TSTypeAssertion"
+      ) {
         return true;
       }
     // else fallthrough

tests/format/typescript/cast/__snapshots__/jsfmt.spec.js.snap

@@ -355,6 +355,10 @@ true || <x>a;
 <x>a + <x>b;
 (<x>a) = 1;
 
+function * g() {
+  const a = <T>(yield b);
+}
+
 =====================================output=====================================
 <DocumentHighlightKind>(a ? b : c);
 <any>(() => {});
@@ -365,6 +369,10 @@ true || <x>a;
 <x>a + <x>b;
 (<x>a) = 1;
 
+function* g() {
+  const a = <T>(yield b);
+}
+
 ================================================================================
 `;
 

tests/format/typescript/cast/parenthesis.ts

@@ -6,3 +6,7 @@
 true || <x>a;
 <x>a + <x>b;
 (<x>a) = 1;
+
+function * g() {
+  const a = <T>(yield b);
+}