fix(43939): forbid converting getters to async/await (#43944)

src/testRunner/unittests/services/convertToAsyncFunction.ts

@@ -1698,6 +1698,14 @@ function [#|f|](x?: number): Promise<void> | number {
     if (x) return x;
     return fetch('').then(() => {});
 }
+`);
+
+        _testConvertToAsyncFunctionFailed("convertToAsyncFunction__NoSuggestionInGetters", `
+class Foo {
+    get [#|m|](): Promise<number> {
+        return Promise.resolve(1).then(n => n);
+    }
+}
 `);
 
     });