Error diagnostic for private classes in inline functions; Fix for KT-7545: IllegalAccessError when accessing private nested class through inlined function from different package

#KT-7545 Fixed

compiler/frontend/src/org/jetbrains/kotlin/diagnostics/Errors.java

@@ -32,7 +32,6 @@ import org.jetbrains.kotlin.resolve.calls.inference.InferenceErrorData;
 import org.jetbrains.kotlin.resolve.calls.model.ResolvedCall;
 import org.jetbrains.kotlin.resolve.varianceChecker.VarianceChecker.VarianceConflictDiagnosticData;
 import org.jetbrains.kotlin.types.KotlinType;
-import org.jetbrains.kotlin.types.TypeProjection;
 
 import java.lang.reflect.Field;
 import java.lang.reflect.Modifier;
@@ -774,6 +773,7 @@ public interface Errors {
 
     //Inline and inlinable parameters
     DiagnosticFactory2<KtElement, DeclarationDescriptor, DeclarationDescriptor> INVISIBLE_MEMBER_FROM_INLINE = DiagnosticFactory2.create(ERROR, CALL_ELEMENT);
+    DiagnosticFactory2<KtElement, DeclarationDescriptor, DeclarationDescriptor> PRIVATE_CLASS_MEMBER_FROM_INLINE = DiagnosticFactory2.create(ERROR, CALL_ELEMENT);
     DiagnosticFactory1<KtElement, KtElement> NON_LOCAL_RETURN_NOT_ALLOWED = DiagnosticFactory1.create(ERROR, CALL_ELEMENT);
     DiagnosticFactory2<KtElement, KtNamedDeclaration, DeclarationDescriptor> NOT_YET_SUPPORTED_IN_INLINE = DiagnosticFactory2.create(ERROR);
     DiagnosticFactory1<PsiElement, DeclarationDescriptor> NOTHING_TO_INLINE = DiagnosticFactory1.create(WARNING);

compiler/frontend/src/org/jetbrains/kotlin/diagnostics/rendering/DefaultErrorMessages.java

@@ -733,6 +733,8 @@ public class DefaultErrorMessages {
 
         //Inline
         MAP.put(INVISIBLE_MEMBER_FROM_INLINE, "Public-API inline function cannot access non-public-API ''{0}''", SHORT_NAMES_IN_TYPES, SHORT_NAMES_IN_TYPES);
+        MAP.put(PRIVATE_CLASS_MEMBER_FROM_INLINE, "Non-private inline function cannot access members of private classes: ''{0}''", SHORT_NAMES_IN_TYPES, SHORT_NAMES_IN_TYPES);
+
         MAP.put(NOT_YET_SUPPORTED_IN_INLINE, "''{0}'' construction is not yet supported in inline functions", ELEMENT_TEXT, SHORT_NAMES_IN_TYPES);
         MAP.put(DECLARATION_CANT_BE_INLINED, "''inline'' modifier is not allowed on virtual members. Only private or final members can be inlined");
         MAP.put(NOTHING_TO_INLINE, "Expected performance impact of inlining ''{0}'' can be insignificant. Inlining works best for functions with lambda parameters", SHORT_NAMES_IN_TYPES);

compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/checkers/InlineChecker.java

@@ -93,7 +93,7 @@ class InlineChecker implements CallChecker {
             }
         }
 
-        checkVisibility(targetDescriptor, expression, context);
+        checkVisibilityAndAccess(targetDescriptor, expression, context);
         checkRecursion(context, targetDescriptor, expression);
     }
 
@@ -238,11 +238,26 @@ class InlineChecker implements CallChecker {
         return isInvoke || InlineUtil.isInline(descriptor);
     }
 
-    private void checkVisibility(@NotNull CallableDescriptor declarationDescriptor, @NotNull KtElement expression, @NotNull BasicCallResolutionContext context){
+    private void checkVisibilityAndAccess(@NotNull CallableDescriptor declarationDescriptor, @NotNull KtElement expression, @NotNull BasicCallResolutionContext context){
         boolean declarationDescriptorIsPublicApi = DescriptorUtilsKt.isEffectivelyPublicApi(declarationDescriptor) || isDefinedInInlineFunction(declarationDescriptor);
         if (isEffectivelyPublicApiFunction && !declarationDescriptorIsPublicApi && declarationDescriptor.getVisibility() != Visibilities.LOCAL) {
             context.trace.report(Errors.INVISIBLE_MEMBER_FROM_INLINE.on(expression, declarationDescriptor, descriptor));
         }
+        else {
+            checkPrivateClassMemberAccess(declarationDescriptor, expression, context);
+        }
+    }
+
+    private void checkPrivateClassMemberAccess(
+            @NotNull DeclarationDescriptor declarationDescriptor,
+            @NotNull KtElement expression,
+            @NotNull BasicCallResolutionContext context
+    ) {
+        if (!Visibilities.isPrivate(descriptor.getVisibility())) {
+            if (DescriptorUtilsKt.isInsidePrivateClass(declarationDescriptor)) {
+                context.trace.report(Errors.PRIVATE_CLASS_MEMBER_FROM_INLINE.on(expression, declarationDescriptor, descriptor));
+            }
+        }
     }
 
     private boolean isDefinedInInlineFunction(@NotNull DeclarationDescriptorWithVisibility startDescriptor) {