Report redeclaration errors for type aliases vs class/interface/object.

compiler/frontend/src/org/jetbrains/kotlin/resolve/DeclarationResolver.kt

@@ -21,6 +21,7 @@ import com.google.common.collect.Multimap
 import com.google.common.collect.Sets
 import com.intellij.psi.PsiElement
 import org.jetbrains.kotlin.descriptors.ClassDescriptor
+import org.jetbrains.kotlin.descriptors.ClassifierDescriptor
 import org.jetbrains.kotlin.descriptors.DeclarationDescriptor
 import org.jetbrains.kotlin.descriptors.PropertyDescriptor
 import org.jetbrains.kotlin.diagnostics.Errors
@@ -54,7 +55,7 @@ class DeclarationResolver(
         for (classDescriptor in c.declaredClasses.values) {
             val descriptorMap = HashMultimap.create<Name, DeclarationDescriptor>()
             for (desc in classDescriptor.unsubstitutedMemberScope.getContributedDescriptors()) {
-                if (desc is ClassDescriptor || desc is PropertyDescriptor) {
+                if (desc is ClassifierDescriptor || desc is PropertyDescriptor) {
                     descriptorMap.put(desc.name, desc)
                 }
             }
@@ -72,7 +73,7 @@ class DeclarationResolver(
             }
             // We mustn't compare PropertyDescriptor with PropertyDescriptor because we do this at OverloadResolver
             for (descriptor in descriptors) {
-                if (descriptor is ClassDescriptor) {
+                if (descriptor is ClassifierDescriptor) {
                     for (descriptor2 in descriptors) {
                         if (descriptor === descriptor2) {
                             continue
@@ -116,7 +117,7 @@ class DeclarationResolver(
         val descriptors = HashSet<DeclarationDescriptor>()
 
         descriptors.addIfNotNull(topLevelDescriptorProvider.getPackageFragment(fqName))
-        descriptors.addAll(topLevelDescriptorProvider.getTopLevelClassDescriptors(fqName, location))
+        descriptors.addAll(topLevelDescriptorProvider.getTopLevelClassifierDescriptors(fqName, location))
         return descriptors
     }
 }

compiler/frontend/src/org/jetbrains/kotlin/resolve/lazy/ResolveSession.java

@@ -45,8 +45,10 @@ import org.jetbrains.kotlin.resolve.lazy.descriptors.LazyPackageDescriptor;
 import org.jetbrains.kotlin.resolve.scopes.LexicalScope;
 import org.jetbrains.kotlin.resolve.scopes.MemberScope;
 import org.jetbrains.kotlin.storage.*;
+import org.jetbrains.kotlin.utils.SmartList;
 
 import javax.inject.Inject;
+import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.List;
@@ -234,15 +236,17 @@ public class ResolveSession implements KotlinCodeAnalyzer, LazyClassContext {
     @Override
     @NotNull
     @ReadOnly
-    public Collection<ClassDescriptor> getTopLevelClassDescriptors(@NotNull FqName fqName, @NotNull final LookupLocation location) {
+    public Collection<ClassifierDescriptor> getTopLevelClassifierDescriptors(@NotNull FqName fqName, @NotNull final LookupLocation location) {
         if (fqName.isRoot()) return Collections.emptyList();
 
         PackageMemberDeclarationProvider provider = declarationProviderFactory.getPackageMemberDeclarationProvider(fqName.parent());
         if (provider == null) return Collections.emptyList();
 
-        return ContainerUtil.mapNotNull(
+        Collection<ClassifierDescriptor> result = new SmartList<ClassifierDescriptor>();
+
+        result.addAll(ContainerUtil.mapNotNull(
                 provider.getClassOrObjectDeclarations(fqName.shortName()),
-                new Function<KtClassLikeInfo, ClassDescriptor>() {
+                new Function<KtClassLikeInfo, ClassifierDescriptor>() {
                     @Override
                     public ClassDescriptor fun(KtClassLikeInfo classLikeInfo) {
                         if (classLikeInfo instanceof KtClassOrObjectInfo) {
@@ -259,7 +263,19 @@ public class ResolveSession implements KotlinCodeAnalyzer, LazyClassContext {
                         }
                     }
                 }
-        );
+        ));
+
+        result.addAll(ContainerUtil.map(
+                provider.getTypeAliasDeclarations(fqName.shortName()),
+                new Function<KtTypeAlias, ClassifierDescriptor>() {
+                    @Override
+                    public ClassifierDescriptor fun(KtTypeAlias alias) {
+                        return (ClassifierDescriptor) lazyDeclarationResolver.resolveToDescriptor(alias);
+                    }
+                }
+        ));
+
+        return result;
     }
 
     @Override

compiler/frontend/src/org/jetbrains/kotlin/resolve/lazy/TopLevelDescriptorProvider.kt

@@ -16,7 +16,7 @@
 
 package org.jetbrains.kotlin.resolve.lazy
 
-import org.jetbrains.kotlin.descriptors.ClassDescriptor
+import org.jetbrains.kotlin.descriptors.ClassifierDescriptor
 import org.jetbrains.kotlin.incremental.components.LookupLocation
 import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.resolve.lazy.descriptors.LazyPackageDescriptor
@@ -24,7 +24,7 @@ import org.jetbrains.kotlin.resolve.lazy.descriptors.LazyPackageDescriptor
 interface TopLevelDescriptorProvider {
     fun getPackageFragment(fqName: FqName): LazyPackageDescriptor?
 
-    fun getTopLevelClassDescriptors(fqName: FqName, location: LookupLocation): Collection<ClassDescriptor>
+    fun getTopLevelClassifierDescriptors(fqName: FqName, location: LookupLocation): Collection<ClassifierDescriptor>
 }
 
 object NoTopLevelDescriptorProvider : TopLevelDescriptorProvider {
@@ -34,7 +34,7 @@ object NoTopLevelDescriptorProvider : TopLevelDescriptorProvider {
         shouldNotBeCalled()
     }
 
-    override fun getTopLevelClassDescriptors(fqName: FqName, location: LookupLocation): Collection<ClassDescriptor> {
+    override fun getTopLevelClassifierDescriptors(fqName: FqName, location: LookupLocation): Collection<ClassifierDescriptor> {
         shouldNotBeCalled()
     }
 }

compiler/frontend/src/org/jetbrains/kotlin/resolve/lazy/descriptors/AbstractLazyMemberScope.kt

@@ -60,7 +60,10 @@ protected constructor(
 
     override fun getContributedClassifier(name: Name, location: LookupLocation): ClassifierDescriptor? {
         recordLookup(name, location)
-        return classDescriptors(name).firstOrNull() ?: typeAliasDescriptors(name).firstOrNull()
+        // NB we should resolve type alias descriptors even if a class descriptor with corresponding name is present
+        val firstClassDescriptor = classDescriptors(name).firstOrNull()
+        val firstTypeAliasDescriptor = typeAliasDescriptors(name).firstOrNull()
+        return firstClassDescriptor ?: firstTypeAliasDescriptor
     }
 
     override fun getContributedFunctions(name: Name, location: LookupLocation): Collection<SimpleFunctionDescriptor> {

compiler/testData/diagnostics/tests/redeclarations/TypeAliasVsClass.kt

@@ -0,0 +1,17 @@
+// FILE: file1.kt
+class <!REDECLARATION!>SomeClass<!>
+
+typealias <!REDECLARATION!>SomeClass<!> = Any
+typealias <!REDECLARATION!>SomeClass<!> = Any
+typealias <!REDECLARATION!>SomeClass<!> = Any
+
+class Outer {
+    class <!REDECLARATION!>Nested<!>
+
+    typealias <!REDECLARATION!>Nested<!> = Any
+    typealias <!REDECLARATION!>Nested<!> = Any
+    typealias <!REDECLARATION!>Nested<!> = Any
+}
+
+// FILE: file2.kt
+typealias <!REDECLARATION!>SomeClass<!> = Any

compiler/testData/diagnostics/tests/redeclarations/TypeAliasVsClass.txt

@@ -0,0 +1,30 @@
+package
+
+public typealias SomeClass = kotlin.Any
+public typealias SomeClass = kotlin.Any
+public typealias SomeClass = kotlin.Any
+public typealias SomeClass = kotlin.Any
+
+public final class Outer {
+    public typealias Nested = kotlin.Any
+    public typealias Nested = kotlin.Any
+    public typealias Nested = kotlin.Any
+    public constructor Outer()
+    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
+
+    public 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
+    }
+}
+
+public final class SomeClass {
+    public constructor SomeClass()
+    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/DiagnosticsTestGenerated.java

@@ -13890,6 +13890,12 @@ public class DiagnosticsTestGenerated extends AbstractDiagnosticsTest {
                 doTest(fileName);
             }
 
+            @TestMetadata("TypeAliasVsClass.kt")
+            public void testTypeAliasVsClass() throws Exception {
+                String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/redeclarations/TypeAliasVsClass.kt");
+                doTest(fileName);
+            }
+
             @TestMetadata("typeParameterWithTwoBounds.kt")
             public void testTypeParameterWithTwoBounds() throws Exception {
                 String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/redeclarations/typeParameterWithTwoBounds.kt");