Minor, improve error messages when serializing error types

compiler/serialization/src/org/jetbrains/kotlin/serialization/AnnotationSerializer.kt

@@ -16,20 +16,24 @@
 
 package org.jetbrains.kotlin.serialization
 
-import org.jetbrains.kotlin.descriptors.annotations.AnnotationDescriptor
+import org.jetbrains.kotlin.builtins.KotlinBuiltIns
 import org.jetbrains.kotlin.descriptors.ClassDescriptor
 import org.jetbrains.kotlin.descriptors.annotations.AnnotationArgumentVisitor
+import org.jetbrains.kotlin.descriptors.annotations.AnnotationDescriptor
 import org.jetbrains.kotlin.resolve.constants.*
 import org.jetbrains.kotlin.serialization.ProtoBuf.Annotation.Argument.Value
 import org.jetbrains.kotlin.serialization.ProtoBuf.Annotation.Argument.Value.Type
+import org.jetbrains.kotlin.types.ErrorUtils
 import org.jetbrains.kotlin.types.JetType
-import org.jetbrains.kotlin.builtins.KotlinBuiltIns
 
 public object AnnotationSerializer {
     public fun serializeAnnotation(annotation: AnnotationDescriptor, stringTable: StringTable): ProtoBuf.Annotation {
         return with(ProtoBuf.Annotation.newBuilder()) {
             val annotationClass = annotation.getType().getConstructor().getDeclarationDescriptor() as? ClassDescriptor
                                   ?: error("Annotation type is not a class: ${annotation.getType()}")
+            if (ErrorUtils.isError(annotationClass)) {
+                error("Unresolved annotation type: ${annotation.getType()}")
+            }
 
             setId(stringTable.getFqNameIndex(annotationClass))
 

compiler/serialization/src/org/jetbrains/kotlin/serialization/StringTable.java

@@ -23,6 +23,7 @@ import org.jetbrains.kotlin.descriptors.DeclarationDescriptor;
 import org.jetbrains.kotlin.descriptors.PackageFragmentDescriptor;
 import org.jetbrains.kotlin.name.FqName;
 import org.jetbrains.kotlin.name.Name;
+import org.jetbrains.kotlin.types.ErrorUtils;
 
 import static org.jetbrains.kotlin.serialization.ProtoBuf.QualifiedNameTable.QualifiedName;
 
@@ -71,6 +72,10 @@ public class StringTable {
     }
 
     public int getFqNameIndex(@NotNull ClassOrPackageFragmentDescriptor descriptor) {
+        if (ErrorUtils.isError(descriptor)) {
+            throw new IllegalStateException("Cannot get FQ name of error class: " + descriptor);
+        }
+
         QualifiedName.Builder builder = QualifiedName.newBuilder();
         if (descriptor instanceof ClassDescriptor) {
             builder.setKind(QualifiedName.Kind.CLASS);

core/descriptors/src/org/jetbrains/kotlin/descriptors/annotations/Annotations.kt

@@ -16,9 +16,7 @@
 
 package org.jetbrains.kotlin.descriptors.annotations
 
-import org.jetbrains.annotations.Nullable
 import org.jetbrains.kotlin.name.FqName
-import java.util.Collections
 
 public trait Annotations : Iterable<AnnotationDescriptor> {
 
@@ -32,7 +30,9 @@ public trait Annotations : Iterable<AnnotationDescriptor> {
 
             override fun findAnnotation(fqName: FqName) = null
 
-            override fun iterator() = Collections.emptyList<AnnotationDescriptor>().iterator()
+            override fun iterator() = emptyList<AnnotationDescriptor>().iterator()
+
+            override fun toString() = "EMPTY"
         }
     }
 }

core/descriptors/src/org/jetbrains/kotlin/descriptors/annotations/AnnotationsImpl.java

@@ -60,4 +60,9 @@ public class AnnotationsImpl implements Annotations {
     public Iterator<AnnotationDescriptor> iterator() {
         return getAnnotationDescriptors().iterator();
     }
+
+    @Override
+    public String toString() {
+        return annotations.toString();
+    }
 }