Added type tests to 17.5

Author: mattpocock

src/04-generics-advanced/17.5-inference-inside-generic-functions.problem.ts

@@ -1,3 +1,5 @@
+import { Equal, Expect } from "../helpers/type-utils";
+
 type Person = {
   name: string;
   age: number;
@@ -14,3 +16,13 @@ export function remapPerson<Key extends keyof Person>(
 
   return value;
 }
+
+const date = remapPerson("birthdate", new Date());
+const num = remapPerson("age", 42);
+const name = remapPerson("name", "John Doe");
+
+type tests = [
+  Expect<Equal<typeof date, Date>>,
+  Expect<Equal<typeof num, number>>,
+  Expect<Equal<typeof name, string>>,
+];

src/04-generics-advanced/17.5-inference-inside-generic-functions.solution.ts

@@ -1,3 +1,5 @@
+import { Equal, Expect } from "../helpers/type-utils";
+
 type Person = {
   name: string;
   age: number;
@@ -14,3 +16,13 @@ export function remapPerson<Key extends keyof Person>(
 
   return value;
 }
+
+const date = remapPerson("birthdate", new Date());
+const num = remapPerson("age", 42);
+const name = remapPerson("name", "John Doe");
+
+type tests = [
+  Expect<Equal<typeof date, Date>>,
+  Expect<Equal<typeof num, number>>,
+  Expect<Equal<typeof name, string>>,
+];