Add tests

Author: ahejlsberg

tests/cases/conformance/types/unknown/unknownControlFlow.ts

@@ -301,3 +301,104 @@ type Foo = { [key: string]: unknown };
 type NullableFoo = Foo | undefined;
 
 type Bar<T extends NullableFoo> = NonNullable<T>[string];
+
+// Generics and intersections with {}
+
+function fx0<T>(value: T & ({} | null)) {
+    if (value === 42) {
+        value;  // T & {}
+    }
+    else {
+        value;  // T & ({} | null)
+    }
+}
+
+function fx1<T extends unknown>(value: T & ({} | null)) {
+    if (value === 42) {
+        value;  // T & {}
+    }
+    else {
+        value;  // T & ({} | null)
+    }
+}
+
+function fx2<T extends {}>(value: T & ({} | null)) {
+    if (value === 42) {
+        value;  // T & {}
+    }
+    else {
+        value;  // T & ({} | null)
+    }
+}
+
+function fx3<T extends {} | undefined>(value: T & ({} | null)) {
+    if (value === 42) {
+        value;  // T & {}
+    }
+    else {
+        value;  // T & ({} | null)
+    }
+}
+
+function fx4<T extends {} | null>(value: T & ({} | null)) {
+    if (value === 42) {
+        value;  // T & {}
+    }
+    else {
+        value;  // T & ({} | null)
+    }
+}
+
+function fx5<T extends {} | null | undefined>(value: T & ({} | null)) {
+    if (value === 42) {
+        value;  // T & {}
+    }
+    else {
+        value;  // T & ({} | null)
+    }
+}
+
+// Double-equals narrowing
+
+function fx10(x: string | number, y: number) {
+    if (x == y) {
+        x;  // string | number
+    }
+    else {
+        x;  // string | number
+    }
+    if (x != y) {
+        x;  // string | number
+    }
+    else {
+        x;  // string | number
+    }
+}
+
+// Repros from #50706
+
+function SendBlob(encoding: unknown) {
+    if (encoding !== undefined && encoding !== 'utf8') {
+        throw new Error('encoding');
+    }
+    encoding;
+};
+
+function doSomething1<T extends unknown>(value: T): T {
+    if (value === undefined) {
+        return value;
+    }
+    if (value === 42) {
+        throw Error('Meaning of life value');
+    }
+    return value;
+}
+
+function doSomething2(value: unknown): void {
+    if (value === undefined) {
+        return;
+    }
+    if (value === 42) {
+        value;
+    }
+}