KT-6920 Reference this marked as deprecated if extension function is deprecated

#KT-6920 fixed

idea/idea-analysis/src/org/jetbrains/kotlin/idea/highlighter/DeprecatedAnnotationVisitor.java

@@ -63,6 +63,11 @@ public class DeprecatedAnnotationVisitor extends AfterAnalysisHighlightingVisito
     @Override
     public void visitReferenceExpression(@NotNull JetReferenceExpression expression) {
         super.visitReferenceExpression(expression);
+
+        if (expression.getParent() instanceof JetThisExpression) {
+            return;
+        }
+
         ResolvedCall resolvedCall = CallUtilPackage.getResolvedCall(expression, bindingContext);
         if (resolvedCall != null && resolvedCall instanceof VariableAsFunctionResolvedCall) {
             // Deprecated for invoke()

idea/testData/highlighter/deprecated/ExtensionFunction.kt

@@ -0,0 +1,5 @@
+deprecated("does nothing good")
+fun Any.doNothing() = this.toString()  // "this" should not be marked as deprecated despite it referes to deprecated function
+
+// NO_CHECK_INFOS
+// NO_CHECK_WEAK_WARNINGS

idea/tests/org/jetbrains/kotlin/idea/highlighter/HighlightingTestGenerated.java

@@ -113,6 +113,12 @@ public class HighlightingTestGenerated extends AbstractHighlightingTest {
             doTest(fileName);
         }
 
+        @TestMetadata("ExtensionFunction.kt")
+        public void testExtensionFunction() throws Exception {
+            String fileName = JetTestUtils.navigationMetadata("idea/testData/highlighter/deprecated/ExtensionFunction.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("Function.kt")
         public void testFunction() throws Exception {
             String fileName = JetTestUtils.navigationMetadata("idea/testData/highlighter/deprecated/Function.kt");