Fixed KT-4085 Usability problem: Can't import protected nested class

#KT-4085 Fixed

compiler/frontend/src/org/jetbrains/kotlin/resolve/QualifiedExpressionResolver.java

@@ -20,6 +20,7 @@ import com.google.common.base.Predicate;
 import com.google.common.collect.Collections2;
 import com.google.common.collect.Lists;
 import com.google.common.collect.Sets;
+import com.intellij.psi.util.PsiTreeUtil;
 import org.jetbrains.annotations.Mutable;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
@@ -486,9 +487,10 @@ public class QualifiedExpressionResolver {
             @NotNull JetScope scopeToCheckVisibility
     ) {
         if (!Visibilities.isVisible(ReceiverValue.IRRELEVANT_RECEIVER, descriptor, scopeToCheckVisibility.getContainingDeclaration())) {
+            Visibility visibility = descriptor.getVisibility();
+            if (PsiTreeUtil.getParentOfType(referenceExpression, JetImportDirective.class) != null && !visibility.mustCheckInImports()) return;
             //noinspection ConstantConditions
-            trace.report(INVISIBLE_REFERENCE.on(referenceExpression, descriptor, descriptor.getVisibility(),
-                                                descriptor.getContainingDeclaration()));
+            trace.report(INVISIBLE_REFERENCE.on(referenceExpression, descriptor, visibility, descriptor.getContainingDeclaration()));
         }
     }
 

compiler/testData/diagnostics/tests/imports/ImportProtectedClass.kt

@@ -0,0 +1,13 @@
+package p
+
+import p.Foo.Nested
+
+open class Foo {
+    protected class Nested
+}
+
+class Bar: Foo() {
+    fun foo(): Nested? = null
+}
+
+fun foo(): <!INVISIBLE_REFERENCE!>Nested<!>? = null

compiler/testData/diagnostics/tests/imports/ImportProtectedClass.txt

@@ -0,0 +1,27 @@
+package
+
+package p {
+    internal fun foo(): p.Foo.Nested?
+
+    internal final class Bar : p.Foo {
+        public constructor Bar()
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        internal final fun foo(): p.Foo.Nested?
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+
+    internal open class Foo {
+        public constructor Foo()
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+        protected final class Nested {
+            public constructor Nested()
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+    }
+}

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

@@ -4811,6 +4811,12 @@ public class JetDiagnosticsTestGenerated extends AbstractJetDiagnosticsTest {
                 doTest(fileName);
             }
 
+            @TestMetadata("ImportProtectedClass.kt")
+            public void testImportProtectedClass() throws Exception {
+                String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/imports/ImportProtectedClass.kt");
+                doTest(fileName);
+            }
+
             @TestMetadata("ImportResolutionOrder.kt")
             public void testImportResolutionOrder() throws Exception {
                 String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/imports/ImportResolutionOrder.kt");