this is inaccessible inside interface (IDEA-94986)

java/java-impl/src/com/intellij/codeInsight/daemon/impl/analysis/HighlightUtil.java

@@ -1305,9 +1305,25 @@ public class HighlightUtil extends HighlightUtilBase {
       return HighlightClassUtil.reportIllegalEnclosingUsage(expr, null, aClass, expr);
     }
 
+    if (expr instanceof PsiThisExpression && PsiTreeUtil.getParentOfType(expr, PsiMethod.class) == null) {
+      if (aClass.isInterface()) {
+        return thisNotFoundInInterfaceInfo(expr);
+      }
+
+      if (aClass instanceof PsiAnonymousClass && PsiTreeUtil.isAncestor(((PsiAnonymousClass)aClass).getArgumentList(), expr, true)) {
+        final PsiClass parentClass = PsiTreeUtil.getParentOfType(aClass, PsiClass.class, true);
+        if (parentClass != null && parentClass.isInterface()) {
+          return thisNotFoundInInterfaceInfo(expr);
+        }
+      }
+    }
     return null;
   }
 
+  private static HighlightInfo thisNotFoundInInterfaceInfo(PsiExpression expr) {
+    return HighlightInfo.createHighlightInfo(HighlightInfoType.ERROR, expr, "Cannot find symbol variable this");
+  }
+
   private static boolean resolvesToImmediateSuperInterface(@NotNull PsiExpression expr,
                                                            @Nullable PsiJavaCodeReferenceElement qualifier,
                                                            @NotNull PsiClass aClass) {

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/advHighlighting/ThisInInterface.java

@@ -0,0 +1,8 @@
+class C implements A {
+    C(A a) {}
+}
+
+interface A {
+    A a = new C(<error descr="Cannot find symbol variable this">this</error>);
+    A a1 = new C(<error descr="Cannot find symbol variable this">this</error>){};
+}

java/java-tests/testSrc/com/intellij/codeInsight/daemon/LightAdvHighlightingTest.java

@@ -359,4 +359,5 @@ public class LightAdvHighlightingTest extends LightDaemonAnalyzerTestCase {
   public void testUnsupportedFeatures() throws Exception { doTest(false, false); }
   public void testThisBeforeSuper() throws Exception { doTest(false, false); }
   public void testExplicitConstructorInvocation() throws Exception { doTest(false, false); }
+  public void testThisInInterface() throws Exception { doTest(false, false); }
 }