Control flow changes for secondary constructors

compiler/testData/diagnostics/tests/secondaryConstructors/unreachableCode.kt

@@ -0,0 +1,38 @@
+class A0 {
+    <!MUST_BE_INITIALIZED_OR_BE_ABSTRACT!>val x: Int<!>
+    constructor() {
+        if (1 == 1) {
+            return
+        }
+        x = 1
+    }
+    constructor(arg: Int) {
+        x = arg
+    }
+}
+
+class A1 {
+    <!MUST_BE_INITIALIZED_OR_BE_ABSTRACT!>val x: Int<!>
+    constructor() {
+        if (1 == 1) {
+            return
+        } else null!!
+        <!UNREACHABLE_CODE!>x = 1<!>
+    }
+}
+
+class A2 {
+    val x: Int
+    constructor() {
+        if (1 == 1) {
+            x = 1
+            return
+        }
+        else {
+            x = 2
+        }
+    }
+    constructor(arg: Int) {
+        x = arg
+    }
+}