KT-5773 Smart cast doesn't work with Nothing on the rhs of "?:"

#KT-5773 FIxed

compiler/frontend/src/org/jetbrains/jet/lang/types/expressions/BasicExpressionTypingVisitor.java

@@ -1064,6 +1064,10 @@ public class BasicExpressionTypingVisitor extends ExpressionTypingVisitor {
         JetType rightType = rightTypeInfo.getType();
 
         DataFlowInfo dataFlowInfo = resolvedCall.getDataFlowInfoForArguments().getResultInfo();
+        if (leftType != null && rightType != null && KotlinBuiltIns.getInstance().isNothingOrNullableNothing(rightType) && !rightType.isNullable()) {
+            DataFlowValue value = DataFlowValueFactory.createDataFlowValue(left, leftType, context.trace.getBindingContext());
+            dataFlowInfo = dataFlowInfo.disequate(value, DataFlowValue.NULL);
+        }
         JetType type = resolvedCall.getResultingDescriptor().getReturnType();
         if (type == null || rightType == null) return JetTypeInfo.create(null, dataFlowInfo);
 

compiler/testData/diagnostics/tests/smartCasts/elvis.kt

@@ -0,0 +1,11 @@
+class C {
+    fun foo() {}
+}
+
+fun test(a: C?, nn: () -> Nothing?) {
+    a ?: nn()
+    a<!UNSAFE_CALL!>.<!>foo()
+
+    a ?: return
+    <!DEBUG_INFO_AUTOCAST!>a<!>.foo()
+}

compiler/tests/org/jetbrains/jet/checkers/JetDiagnosticsTestGenerated.java

@@ -9014,6 +9014,12 @@ public class JetDiagnosticsTestGenerated extends AbstractJetDiagnosticsTest {
                 doTest(fileName);
             }
             
+            @TestMetadata("elvis.kt")
+            public void testElvis() throws Exception {
+                String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/smartCasts/elvis.kt");
+                doTest(fileName);
+            }
+            
             @TestMetadata("kt1461.kt")
             public void testKt1461() throws Exception {
                 String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/smartCasts/kt1461.kt");