Add tests

Author: ahejlsberg

tests/cases/compiler/reachabilityChecks4.ts

@@ -12,4 +12,55 @@ function foo(x, y) {
         case 4:
             return 3;
     }
-}
+}
+
+declare function noop(): void;
+declare function fail(): never;
+
+function f1(x: 0 | 1 | 2) {
+    switch (x) {
+        case 0:
+            fail();
+        case 1:
+            noop();
+        case 2:
+            return;
+    }
+}
+
+// Repro from #34021
+
+type Behavior = 'SLIDE' | 'SLIDE_OUT'
+type Direction = 'LEFT' | 'RIGHT' | 'TOP' | 'BOTTOM'
+
+interface Transition {
+  behavior: Behavior
+  direction: Direction
+}
+
+function f2(transition: Transition): any {
+    switch (transition.behavior) {
+        case 'SLIDE':
+            switch (transition.direction) {
+                case 'LEFT':
+                    return []
+                case 'RIGHT':
+                    return []
+                case 'TOP':
+                    return []
+                case 'BOTTOM':
+                    return []
+            }
+        case 'SLIDE_OUT':
+            switch (transition.direction) {
+                case 'LEFT':
+                    return []
+                case 'RIGHT':
+                    return []
+                case 'TOP':
+                    return []
+                case 'BOTTOM':
+                    return []
+            }
+    }
+}