Add regression test

Author: ahejlsberg

tests/cases/conformance/types/literal/templateLiteralTypes1.ts

@@ -215,3 +215,25 @@ type AA<T extends number, Q extends number> =
     [true, true] extends [IsNegative<T>, IsNegative<Q>] ? 'Every thing is ok!' : ['strange', IsNegative<T>, IsNegative<Q>];
 
 type BB = AA<-2, -2>;
+
+// Repro from #40970
+
+type PathKeys<T> =
+    T extends readonly any[] ? Extract<keyof T, `${number}`> | SubKeys<T, Extract<keyof T, `${number}`>> :
+    T extends object ? Extract<keyof T, string> | SubKeys<T, Extract<keyof T, string>> :
+    never;
+
+type SubKeys<T, K extends string> = K extends keyof T ? `${K}.${PathKeys<T[K]>}` : never;
+
+declare function getProp2<T, P extends PathKeys<T>>(obj: T, path: P): PropType<T, P>;
+
+const obj2 = {
+    name: 'John',
+    age: 42,
+    cars: [
+        { make: 'Ford', age: 10 },
+        { make: 'Trabant', age: 35 }
+    ]
+} as const;
+
+let make = getProp2(obj2, 'cars.1.make');  // 'Trabant'