DFA: only stable values or qualified with stable receiver can be bound in x = y #KT-15792 Fixed

compiler/testData/diagnostics/tests/smartCasts/varnotnull/boundInitializerWrong.kt

@@ -0,0 +1,45 @@
+// KT-15792 and related
+
+fun foo() {
+    var x: String? = ""
+    val y = x
+    x = null
+    if (y != null) {
+        <!DEBUG_INFO_CONSTANT!>x<!><!UNSAFE_CALL!>.<!>hashCode()
+    }
+}
+
+fun foo2() {
+    var x: String? = ""
+    val y = x
+    if (y != null) {
+        x<!UNSAFE_CALL!>.<!>hashCode()
+    }
+}
+
+fun bar(s: String?) {
+    var ss = s
+    val hashCode = ss?.hashCode()
+    ss = null
+    if (hashCode != null) {
+        <!DEBUG_INFO_CONSTANT!>ss<!><!UNSAFE_CALL!>.<!>hashCode()
+    }
+}
+
+fun bar2(s: String?) {
+    var ss = s
+    val hashCode = ss?.hashCode()
+    if (hashCode != null) {
+        ss<!UNSAFE_CALL!>.<!>hashCode()
+    }
+}
+
+class Some(var s: String?)
+
+fun baz(arg: Some?) {
+    val ss = arg?.s
+    if (ss != null) {
+        <!DEBUG_INFO_SMARTCAST!>arg<!>.hashCode()
+        <!SMARTCAST_IMPOSSIBLE!><!DEBUG_INFO_SMARTCAST!>arg<!>.s<!>.hashCode()
+    }
+}

compiler/testData/diagnostics/tests/smartCasts/varnotnull/boundInitializerWrong.txt

@@ -0,0 +1,15 @@
+package
+
+public fun bar(/*0*/ s: kotlin.String?): kotlin.Unit
+public fun bar2(/*0*/ s: kotlin.String?): kotlin.Unit
+public fun baz(/*0*/ arg: Some?): kotlin.Unit
+public fun foo(): kotlin.Unit
+public fun foo2(): kotlin.Unit
+
+public final class Some {
+    public constructor Some(/*0*/ s: kotlin.String?)
+    public final var s: kotlin.String?
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}