Render warning on 'class object' as deprecated

idea/idea-analysis/src/org/jetbrains/kotlin/idea/highlighter/JetPsiChecker.kt

@@ -23,6 +23,7 @@ import com.intellij.lang.annotation.Annotation
 import com.intellij.lang.annotation.AnnotationHolder
 import com.intellij.lang.annotation.Annotator
 import com.intellij.openapi.application.ApplicationManager
+import com.intellij.openapi.editor.colors.CodeInsightColors
 import com.intellij.openapi.editor.colors.TextAttributesKey
 import com.intellij.openapi.progress.ProcessCanceledException
 import com.intellij.psi.MultiRangeReference
@@ -147,6 +148,9 @@ public open class JetPsiChecker : Annotator, HighlightRangeExtension {
                     }
                     for (textRange in textRanges) {
                         val annotation = holder.createWarningAnnotation(textRange, getDefaultMessage(diagnostic))
+
+                        if (factory == Errors.DEPRECATED_CLASS_OBJECT_SYNTAX) annotation.setTextAttributes(CodeInsightColors.DEPRECATED_ATTRIBUTES)
+
                         setUpAnnotation(diagnostic, annotation, if (factory in Errors.UNUSED_ELEMENT_DIAGNOSTICS)
                             ProblemHighlightType.LIKE_UNUSED_SYMBOL
                         else

idea/testData/checker/DeprecatedClassObjectSyntax.kt

@@ -0,0 +1,17 @@
+class A {
+    <warning textAttributesKey="DEPRECATED_ATTRIBUTES">class object</warning> {
+
+    }
+}
+
+class B {
+    <warning textAttributesKey="DEPRECATED_ATTRIBUTES">class object C</warning> {
+
+    }
+}
+
+class C {
+    default <warning textAttributesKey="DEPRECATED_ATTRIBUTES">class object G</warning> {
+
+    }
+}

idea/tests/org/jetbrains/kotlin/checkers/JetPsiCheckerTestGenerated.java

@@ -136,6 +136,12 @@ public class JetPsiCheckerTestGenerated extends AbstractJetPsiCheckerTest {
             doTest(fileName);
         }
 
+        @TestMetadata("DeprecatedClassObjectSyntax.kt")
+        public void testDeprecatedClassObjectSyntax() throws Exception {
+            String fileName = JetTestUtils.navigationMetadata("idea/testData/checker/DeprecatedClassObjectSyntax.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("ExtensionFunctions.kt")
         public void testExtensionFunctions() throws Exception {
             String fileName = JetTestUtils.navigationMetadata("idea/testData/checker/ExtensionFunctions.kt");