Add some data flow analysis tests on when

compiler/testData/diagnostics/tests/when/withSubjectVariable/jumpoutInInitializer.kt

@@ -0,0 +1,43 @@
+// !LANGUAGE: +VariableDeclarationInWhenSubject
+// !DIAGNOSTICS: -UNUSED_VARIABLE
+
+
+fun testJumpOutInElvis(x: Int?) {
+    loop@ while (true) {
+        val y = when (val z = x ?: break@loop) {
+            0 -> "0"
+            else -> "not 0"
+        }
+
+        <!DEBUG_INFO_SMARTCAST!>x<!>.inc()
+    }
+
+    x<!UNSAFE_CALL!>.<!>inc()
+}
+
+fun testJumpOutInElvisLikeIf(x: Int?) {
+    loop@ while (true) {
+        val y = when (val z = if (x == null) break@loop else <!DEBUG_INFO_SMARTCAST!>x<!>) {
+            0 -> "0"
+            else -> "not 0"
+        }
+        <!DEBUG_INFO_SMARTCAST!>x<!>.inc()
+    }
+
+    x<!UNSAFE_CALL!>.<!>inc()
+}
+
+
+fun getBoolean() = true
+
+fun testJumpOutInIf(x: Int?) {
+    loop@ while (true) {
+        val y = when (val z = if (getBoolean()) { x!!; break@loop } else x) {
+            0 -> "0"
+            else -> "not 0"
+        }
+        x<!UNSAFE_CALL!>.<!>inc()
+    }
+
+    x<!UNSAFE_CALL!>.<!>inc() // Actually, safe, but it's OK if it's error
+}