Add tests

Author: ahejlsberg

tests/cases/conformance/controlFlow/assertionTypePredicates1.ts

@@ -126,3 +126,14 @@ declare class Wat {
     get p2(): asserts this is string;
     set p2(x: asserts this is string);
 }
+
+function f20(x: unknown) {
+    const assert = (value: unknown): asserts value => {}
+    assert(typeof x === "string");  // Error
+    const a = [assert];
+    a[0](typeof x === "string");  // Error
+    const t1 = new Test();
+    t1.assert(typeof x === "string");  // Error
+    const t2: Test = new Test();
+    t2.assert(typeof x === "string");
+}

tests/cases/conformance/controlFlow/neverReturningFunctions1.ts

@@ -157,6 +157,13 @@ function f42(x: number) {
     x;  // Unreachable
 }
 
+function f43() {
+    const fail = (): never => { throw new Error(); };
+    const f = [fail];
+    fail();  // Error
+    f[0]();  // Error
+}
+
 // Repro from #33582
 
 export interface Component<T extends object = any> {