Extract and convert 'findLoopsInSupertypesAndDisconnect'

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

@@ -0,0 +1,61 @@
+/*
+ * Copyright 2010-2015 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+@file:JvmName("FindLoopsInSupertypes")
+package org.jetbrains.kotlin.resolve
+
+import org.jetbrains.kotlin.types.KotlinType
+import org.jetbrains.kotlin.types.TypeConstructor
+import org.jetbrains.kotlin.utils.DFS
+
+fun findLoopsInSupertypesAndDisconnect(
+        currentTypeConstructor: TypeConstructor,
+        superTypes: MutableCollection<KotlinType>,
+        neighbors: (TypeConstructor) -> Iterable<KotlinType>,
+        reportLoopAt: (KotlinType) -> Unit
+) {
+
+    val graph = DFS.Neighbors<TypeConstructor> { node -> neighbors(node).map { it.constructor } }
+
+    val iterator = superTypes.iterator()
+    while (iterator.hasNext()) {
+        val item = iterator.next()
+        if (isReachable(item.constructor, currentTypeConstructor, graph)) {
+            iterator.remove()
+            reportLoopAt(item)
+        }
+    }
+}
+
+private fun isReachable(
+        from: TypeConstructor, to: TypeConstructor,
+        neighbors: DFS.Neighbors<TypeConstructor>
+): Boolean {
+    var result = false
+    DFS.dfs(listOf(from), neighbors, DFS.VisitedWithSet(), object : DFS.AbstractNodeHandler<TypeConstructor, Unit>() {
+        override fun beforeChildren(current: TypeConstructor): Boolean {
+            if (current == to) {
+                result = true
+                return false
+            }
+            return true
+        }
+
+        override fun result() = Unit
+    })
+
+    return result
+}

compiler/frontend/src/org/jetbrains/kotlin/resolve/lazy/descriptors/LazyClassDescriptor.java

@@ -582,18 +582,27 @@ public class LazyClassDescriptor extends ClassDescriptorBase implements ClassDes
         }
 
         private void findAndDisconnectLoopsInTypeHierarchy(@Mutable Collection<KotlinType> supertypes) {
-            for (Iterator<KotlinType> iterator = supertypes.iterator(); iterator.hasNext(); ) {
-                KotlinType supertype = iterator.next();
-                if (isReachable(supertype.getConstructor(), this, new HashSet<TypeConstructor>())) {
-                    iterator.remove();
+            FindLoopsInSupertypes.findLoopsInSupertypesAndDisconnect(
+                    typeConstructor, supertypes,
+                    new Function1<TypeConstructor, Iterable<? extends KotlinType>>() {
+                        @Override
+                        public Iterable<? extends KotlinType> invoke(TypeConstructor typeConstructor) {
+                            return getNeighbors(typeConstructor);
+                        }
+                    },
+                    new Function1<KotlinType, Unit>() {
+                        @Override
+                        public Unit invoke(KotlinType type) {
+                            ClassifierDescriptor supertypeDescriptor = type.getConstructor().getDeclarationDescriptor();
+                            if (supertypeDescriptor instanceof ClassDescriptor) {
+                                ClassDescriptor superclass = (ClassDescriptor) supertypeDescriptor;
+                                reportCyclicInheritanceHierarchyError(c.getTrace(), LazyClassDescriptor.this, superclass);
+                            }
 
-                    ClassifierDescriptor supertypeDescriptor = supertype.getConstructor().getDeclarationDescriptor();
-                    if (supertypeDescriptor instanceof ClassDescriptor) {
-                        ClassDescriptor superclass = (ClassDescriptor) supertypeDescriptor;
-                        reportCyclicInheritanceHierarchyError(c.getTrace(), LazyClassDescriptor.this, superclass);
+                            return Unit.INSTANCE;
+                        }
                     }
-                }
-            }
+            );
         }
 
         private void reportCyclicInheritanceHierarchyError(
@@ -627,20 +636,6 @@ public class LazyClassDescriptor extends ClassDescriptorBase implements ClassDes
             }
         }
 
-        private boolean isReachable(TypeConstructor from, TypeConstructor to, Set<TypeConstructor> visited) {
-            if (!visited.add(from)) return false;
-            for (KotlinType supertype : getNeighbors(from)) {
-                TypeConstructor supertypeConstructor = supertype.getConstructor();
-                if (supertypeConstructor == to) {
-                    return true;
-                }
-                if (isReachable(supertypeConstructor, to, visited)) {
-                    return true;
-                }
-            }
-            return false;
-        }
-
         private Collection<KotlinType> getNeighbors(TypeConstructor from) {
             // Supertypes + type for container
             Collection<KotlinType> neighbours = new ArrayList<KotlinType>(