Tests for KT-13468 / KT-13765

(cherry picked from commit 2e4c0b4)

compiler/testData/diagnostics/tests/smartCasts/variables/ifNullAssignment.kt

@@ -0,0 +1,72 @@
+// See KT-13468, KT-13765
+
+fun basic(): String {
+    var current: String? = null
+    current = if (current == null) "bar" else current
+    return <!TYPE_MISMATCH!>current<!>
+}
+
+fun foo(flag: Boolean) {
+    var x: String? = null
+
+    if (x == null) {
+        x = if (flag) "34" else "12"
+    }
+
+    x<!UNSAFE_CALL!>.<!>hashCode()
+}
+
+fun bar(flag: Boolean) {
+    var x: String? = null
+
+    if (x == null) {
+        x = when {
+            flag -> "34"
+            else -> "12"
+        }
+    }
+
+    x<!UNSAFE_CALL!>.<!>hashCode()
+}
+
+fun baz(flag: Boolean) {
+    var x: String? = null
+
+    if (x == null) {
+        x = if (flag) {
+            "34"
+        } else {
+            "12"
+        }
+    }
+
+    x<!UNSAFE_CALL!>.<!>hashCode()
+}
+
+fun gav(flag: Boolean, arg: String?) {
+    var x: String? = null
+
+    if (x == null) {
+        x = arg ?: if (flag) {
+            "34"
+        } else {
+            "12"
+        }
+    }
+
+    <!DEBUG_INFO_SMARTCAST!>x<!>.hashCode()
+}
+
+fun gau(flag: Boolean, arg: String?) {
+    var x: String? = null
+
+    if (x == null) {
+        x = if (flag) {
+            arg ?: "34"
+        } else {
+            arg ?: "12"
+        }
+    }
+
+    x<!UNSAFE_CALL!>.<!>hashCode()
+}

compiler/testData/diagnostics/tests/smartCasts/variables/ifNullAssignment.txt

@@ -0,0 +1,8 @@
+package
+
+public fun bar(/*0*/ flag: kotlin.Boolean): kotlin.Unit
+public fun basic(): kotlin.String
+public fun baz(/*0*/ flag: kotlin.Boolean): kotlin.Unit
+public fun foo(/*0*/ flag: kotlin.Boolean): kotlin.Unit
+public fun gau(/*0*/ flag: kotlin.Boolean, /*1*/ arg: kotlin.String?): kotlin.Unit
+public fun gav(/*0*/ flag: kotlin.Boolean, /*1*/ arg: kotlin.String?): kotlin.Unit

compiler/tests/org/jetbrains/kotlin/checkers/DiagnosticsTestGenerated.java

@@ -20424,6 +20424,12 @@ public class DiagnosticsTestGenerated extends AbstractDiagnosticsTest {
                     doTest(fileName);
                 }
 
+                @TestMetadata("ifNullAssignment.kt")
+                public void testIfNullAssignment() throws Exception {
+                    String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/smartCasts/variables/ifNullAssignment.kt");
+                    doTest(fileName);
+                }
+
                 @TestMetadata("ifVarIs.kt")
                 public void testIfVarIs() throws Exception {
                     String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/smartCasts/variables/ifVarIs.kt");