Extract Function: Approximate non-resolvable types with nearest resolvable supertype when possible

#KT-7120 Fixed

idea/ide-common/src/org/jetbrains/kotlin/idea/util/ImportsUtils.kt

@@ -0,0 +1,71 @@
+/*
+ * 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.
+ */
+
+package org.jetbrains.kotlin.idea.imports
+
+import org.jetbrains.kotlin.descriptors.DeclarationDescriptor
+import org.jetbrains.kotlin.name.FqName
+import org.jetbrains.kotlin.descriptors.ConstructorDescriptor
+import org.jetbrains.kotlin.descriptors.PackageViewDescriptor
+import org.jetbrains.kotlin.descriptors.ClassDescriptor
+import org.jetbrains.kotlin.descriptors.CallableDescriptor
+import org.jetbrains.kotlin.psi.psiUtil.getReceiverExpression
+import com.intellij.psi.PsiElement
+import org.jetbrains.kotlin.types.JetType
+import org.jetbrains.kotlin.resolve.descriptorUtil.getImportableDescriptor
+import org.jetbrains.kotlin.resolve.descriptorUtil.isExtension
+import org.jetbrains.kotlin.psi.*
+import org.jetbrains.kotlin.resolve.*
+
+public val DeclarationDescriptor.importableFqName: FqName?
+    get() {
+        val mayBeUnsafe = DescriptorUtils.getFqName(getImportableDescriptor())
+        return if (mayBeUnsafe.isSafe()) mayBeUnsafe.toSafe() else null
+    }
+
+public val DeclarationDescriptor.importableFqNameSafe: FqName
+    get() = DescriptorUtils.getFqNameSafe(getImportableDescriptor())
+
+public fun DeclarationDescriptor.canBeReferencedViaImport(): Boolean {
+    if (this is PackageViewDescriptor ||
+        DescriptorUtils.isTopLevelDeclaration(this) ||
+        (this is CallableDescriptor && DescriptorUtils.isStaticDeclaration(this))) {
+        return !getName().isSpecial()
+    }
+
+    val parentClass = getContainingDeclaration() as? ClassDescriptor ?: return false
+    if (!parentClass.canBeReferencedViaImport()) return false
+
+    return when (this) {
+        is ConstructorDescriptor -> !parentClass.isInner() // inner class constructors can't be referenced via import
+        is ClassDescriptor -> true
+        else -> false
+    }
+}
+
+public fun JetType.canBeReferencedViaImport(): Boolean {
+    val descriptor = getConstructor().getDeclarationDescriptor()
+    return descriptor != null && descriptor.canBeReferencedViaImport()
+}
+
+// for cases when class qualifier refers companion object treats it like reference to class itself
+public fun JetReferenceExpression.getImportableTargets(bindingContext: BindingContext): Collection<DeclarationDescriptor> {
+    val targets = bindingContext[BindingContext.SHORT_REFERENCE_TO_COMPANION_OBJECT, this]?.let { listOf(it) }
+                     ?: bindingContext[BindingContext.REFERENCE_TARGET, this]?.let { listOf(it) }
+                     ?: bindingContext[BindingContext.AMBIGUOUS_REFERENCE_TARGET, this]
+                     ?: listOf()
+    return targets.map { it.getImportableDescriptor() }.toSet()
+}

idea/ide-common/src/org/jetbrains/kotlin/idea/util/TypeUtils.kt

@@ -20,7 +20,10 @@ import org.jetbrains.kotlin.types.*
 import org.jetbrains.kotlin.builtins.KotlinBuiltIns
 import org.jetbrains.kotlin.resolve.jvm.kotlinSignature.CollectionClassMapping
 import org.jetbrains.kotlin.descriptors.ClassDescriptor
+import org.jetbrains.kotlin.descriptors.TypeParameterDescriptor
+import org.jetbrains.kotlin.idea.imports.canBeReferencedViaImport
 import org.jetbrains.kotlin.load.java.JvmAnnotationNames
+import org.jetbrains.kotlin.resolve.scopes.JetScope
 import java.util.LinkedHashSet
 import org.jetbrains.kotlin.types.typeUtil.substitute
 
@@ -87,3 +90,19 @@ public fun JetType.nullability(): TypeNullability {
         else -> TypeNullability.NOT_NULL
     }
 }
+
+fun JetType.isResolvableInScope(scope: JetScope?, checkTypeParameters: Boolean): Boolean {
+    if (canBeReferencedViaImport()) return true
+
+    val descriptor = getConstructor().getDeclarationDescriptor()
+    if (descriptor == null || descriptor.getName().isSpecial()) return false
+    if (!checkTypeParameters && descriptor is TypeParameterDescriptor) return true
+
+    return scope != null && scope.getClassifier(descriptor.getName()) == descriptor
+}
+
+public fun JetType.approximateWithResolvableType(scope: JetScope?, checkTypeParameters: Boolean): JetType {
+    if (isError() || isResolvableInScope(scope, checkTypeParameters)) return this
+    return supertypes().firstOrNull { it.isResolvableInScope(scope, checkTypeParameters) }
+           ?: KotlinBuiltIns.getInstance().getAnyType()
+}