KT-7452 Code completion does not honor smart casts for 'this'

#KT-7452 Fixed

idea/ide-common/src/org/jetbrains/kotlin/idea/codeInsight/ReferenceVariantsHelper.kt

@@ -111,16 +111,18 @@ public class ReferenceVariantsHelper(
             return descriptors
         }
         else {
+            val dataFlowInfo = context.getDataFlowInfo(expression)
+
             val descriptorsSet = HashSet<DeclarationDescriptor>()
 
             // process instance members that can be called via implicit receiver's instances
             val receivers = resolutionScope.getImplicitReceiversWithInstance()
-            for (receiver in receivers) {
-                descriptorsSet.addMembersFromReceiver(receiver.getType(), CallType.NORMAL, kindFilter, nameFilter)
-            }
-
-            val dataFlowInfo = context.getDataFlowInfo(expression)
             val receiverValues = receivers.map { it.getValue() }
+            for (receiverValue in receiverValues) {
+                for (variant in SmartCastUtils.getSmartCastVariantsWithLessSpecificExcluded(receiverValue, context, containingDeclaration, dataFlowInfo)) {
+                    descriptorsSet.addMembersFromReceiver(variant, CallType.NORMAL, kindFilter, nameFilter)
+                }
+            }
 
             // process extensions and non-instance members
             for (descriptor in resolutionScope.getDescriptorsFiltered(kindFilter, nameFilter)) {

idea/idea-completion/testData/basic/common/SmartCastThis.kt

@@ -0,0 +1,21 @@
+class C {
+    fun bar(){}
+}
+
+open class X {
+    fun Any.foo() {
+        if (this is C && this@X is Y) {
+            <caret>
+        }
+    }
+}
+
+class Y : X() {
+    fun y()
+}
+
+fun C.extFun(){}
+
+// EXIST: bar
+// EXIST: y
+// EXIST: extFun

idea/idea-completion/tests/org/jetbrains/kotlin/idea/completion/test/JSBasicCompletionTestGenerated.java

@@ -931,6 +931,12 @@ public class JSBasicCompletionTestGenerated extends AbstractJSBasicCompletionTes
             doTest(fileName);
         }
 
+        @TestMetadata("SmartCastThis.kt")
+        public void testSmartCastThis() throws Exception {
+            String fileName = JetTestUtils.navigationMetadata("idea/idea-completion/testData/basic/common/SmartCastThis.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("StandardJetArrayFirst.kt")
         public void testStandardJetArrayFirst() throws Exception {
             String fileName = JetTestUtils.navigationMetadata("idea/idea-completion/testData/basic/common/StandardJetArrayFirst.kt");

idea/idea-completion/tests/org/jetbrains/kotlin/idea/completion/test/JvmBasicCompletionTestGenerated.java

@@ -931,6 +931,12 @@ public class JvmBasicCompletionTestGenerated extends AbstractJvmBasicCompletionT
             doTest(fileName);
         }
 
+        @TestMetadata("SmartCastThis.kt")
+        public void testSmartCastThis() throws Exception {
+            String fileName = JetTestUtils.navigationMetadata("idea/idea-completion/testData/basic/common/SmartCastThis.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("StandardJetArrayFirst.kt")
         public void testStandardJetArrayFirst() throws Exception {
             String fileName = JetTestUtils.navigationMetadata("idea/idea-completion/testData/basic/common/StandardJetArrayFirst.kt");