test: test properties both directly and indirectly on a type

src/types/getters.test.ts

@@ -2,18 +2,18 @@ import * as ts from "typescript";
 import { describe, expect, it } from "vitest";
 
 import { createSourceFileAndTypeChecker } from "../test/utils.js";
+import { isTsVersionAtLeast } from "../utils.js";
 import { getWellKnownSymbolPropertyOfType } from "./getters.js";
 
 describe("getWellKnownSymbolPropertyOfType", () => {
-	// /~https://github.com/JoshuaKGoldberg/ts-api-tools/issues/15
-	it("gets the property when it does not have a value declaration", () => {
+	it("finds the symbol for an `asyncIterator` property", () => {
 		const { sourceFile, typeChecker } = createSourceFileAndTypeChecker(`
-            declare const x: {
-                [Symbol.asyncIterator](): AsyncIterator<any>;
-            }
-        `);
+			declare const x: {
+				[Symbol.asyncIterator](): AsyncIterator<any>;
+			}>
+		`);
 
-		const node = (sourceFile.statements[0] as ts.VariableStatement)
+		const node = (sourceFile.statements[0] as ts.VariaybleStatement)
 			.declarationList.declarations[0].name;
 
 		const type = typeChecker.getTypeAtLocation(node);
@@ -24,4 +24,26 @@ describe("getWellKnownSymbolPropertyOfType", () => {
 			name: /^__@asyncIterator/,
 		});
 	});
+
+	if (isTsVersionAtLeast(4, 3)) {
+		// /~https://github.com/JoshuaKGoldberg/ts-api-tools/issues/15
+		it("finds the symbol for an `asyncIterator` property when that property isn't directly on the type", () => {
+			const { sourceFile, typeChecker } = createSourceFileAndTypeChecker(`
+			declare const x: Omit<{
+				[Symbol.asyncIterator](): AsyncIterator<any>;
+			}, 'z'>
+		`);
+
+			const node = (sourceFile.statements[0] as ts.VariaybleStatement)
+				.declarationList.declarations[0].name;
+
+			const type = typeChecker.getTypeAtLocation(node);
+
+			expect(
+				getWellKnownSymbolPropertyOfType(type, "asyncIterator", typeChecker)
+			).toMatchObject({
+				name: /^__@asyncIterator/,
+			});
+		});
+	}
 });