JetDiagnosticsTest migrated to TestGenerator

- test data files renamed from *.jet to *.kt

compiler/testData/diagnostics/tests/nullabilityAndAutoCasts/kt2146.kt

@@ -0,0 +1,53 @@
+//KT-2146 Nullability casts in when.
+package kt2146
+
+fun f1(s: Int?): Int {
+    return when (s) {
+        null -> 3
+        else -> s
+    }
+}
+
+fun f2(s: Int?): Int {
+    return when (s) {
+        !is Int -> <!TYPE_MISMATCH!>s<!>
+        else -> s
+    }
+}
+
+fun f3(s: Int?): Int {
+    return when (s) {
+        is Int -> s
+        else -> <!TYPE_MISMATCH!>s<!>
+    }
+}
+
+fun f4(s: Int?): Int {
+    return when {
+        s == 4 -> s
+        s == null -> <!TYPE_MISMATCH!>s<!>
+        else -> s
+    }
+}
+
+fun f5(s: Int?): Int {
+    return when (s) {
+        s!! -> s
+        s -> <!TYPE_MISMATCH!>s<!>
+        else -> 0
+    }
+}
+
+fun f6(s: Int?): Int {
+    return when {
+        s is Int -> s
+        else -> <!TYPE_MISMATCH!>s<!>
+    }
+}
+
+fun f7(s: Int?): Int {
+    return when {
+        s !is Int -> <!TYPE_MISMATCH!>s<!>
+        else -> s
+    }
+}