Add tests

tests/cases/conformance/expressions/typeGuards/typeGuardOfFormTypeOfFunction.ts

@@ -0,0 +1,73 @@
+
+function f1(x: any) {
+    if (typeof x === "function") {
+        x;  // any
+    }
+}
+
+function f2(x: unknown) {
+    if (typeof x === "function") {
+        x;  // Function
+    }
+}
+
+function f3(x: {}) {
+    if (typeof x === "function") {
+        x;  // Function
+    }
+}
+
+function f4<T>(x: T) {
+    if (typeof x === "function") {
+        x;  // T & Function
+    }
+}
+
+function f5(x: { s: string }) {
+    if (typeof x === "function") {
+        x;  // never
+    }
+}
+
+function f6(x: () => string) {
+    if (typeof x === "function") {
+        x;  // () => string
+    }
+}
+
+function f10(x: string | (() => string)) {
+    if (typeof x === "function") {
+        x;  // () => string
+    }
+    else {
+        x;  // string
+    }
+}
+
+function f11(x: { s: string } | (() => string)) {
+    if (typeof x === "function") {
+        x;  // () => string
+    }
+    else {
+        x;  // { s: string }
+    }
+}
+
+function f12(x: { s: string } | { n: number }) {
+    if (typeof x === "function") {
+        x;  // never
+    }
+    else {
+        x;  // { s: string } | { n: number }
+    }
+}
+
+// Repro from #18238
+
+function f100<T, K extends keyof T>(obj: T, keys: K[]) : void {
+    for (const k of keys) {
+        const item = obj[k];
+        if (typeof item == 'function')
+            item.call(obj);
+    }
+}