add failing tests

Author: uhyo

tests/src/es5.ts

@@ -437,6 +437,26 @@ expectType<{ foo: number; bar: string; baz: boolean }>(
     expectType<[2, 2, 2]>(a2);
   }
   expectType<[string, string, string]>(a2.map(() => "foo"));
+
+  // https://github.com/uhyo/better-typescript-lib/issues/35
+  function template(strings: TemplateStringsArray, ...keys: string[]): string {
+    const mapped = strings.map((v) => v);
+    expectType<number>(mapped.length);
+  }
+  {
+    class ArrX extends Array<number> {
+      constructor(nums: number[]) {
+        super(...nums);
+      }
+
+      sum(): number {
+        return this.reduce((s, n) => s + n, 0);
+      }
+    }
+    const arrX = new ArrX([2, 3, 4]);
+    const mapped = arrX.map((v) => String(v));
+    expectType<number>(mapped.length);
+  }
 }
 
 // ArrayConstructor