Introduce OptionalExpectationInspection

It works at INFORMATION level only and is intended to form quick-fixes
to add relevant actual declarations.

#KT-25533 Fixed

idea/src/META-INF/plugin.xml

@@ -3057,6 +3057,15 @@ The Kotlin plugin provides language support in IntelliJ IDEA and Android Studio.
                      language="kotlin"
     />
 
+    <localInspection implementationClass="org.jetbrains.kotlin.idea.inspections.OptionalExpectationInspection"
+                     displayName="Optionally expected annotation has no actual annotation"
+                     groupPath="Kotlin"
+                     groupName="Style issues"
+                     enabledByDefault="true"
+                     level="INFORMATION"
+                     language="kotlin"
+    />
+
     <referenceImporter implementation="org.jetbrains.kotlin.idea.quickfix.KotlinReferenceImporter"/>
 
     <fileType.fileViewProviderFactory filetype="KJSM" implementationClass="com.intellij.psi.ClassFileViewProviderFactory"/>

idea/src/META-INF/plugin.xml.173

@@ -3055,6 +3055,15 @@ The Kotlin plugin provides language support in IntelliJ IDEA and Android Studio.
                      language="kotlin"
     />
 
+    <localInspection implementationClass="org.jetbrains.kotlin.idea.inspections.OptionalExpectationInspection"
+                     displayName="Optionally expected annotation has no actual annotation"
+                     groupPath="Kotlin"
+                     groupName="Style issues"
+                     enabledByDefault="true"
+                     level="INFORMATION"
+                     language="kotlin"
+    />
+
     <referenceImporter implementation="org.jetbrains.kotlin.idea.quickfix.KotlinReferenceImporter"/>
 
     <fileType.fileViewProviderFactory filetype="KJSM" implementationClass="com.intellij.psi.ClassFileViewProviderFactory"/>

idea/src/META-INF/plugin.xml.181

@@ -3056,6 +3056,15 @@ The Kotlin plugin provides language support in IntelliJ IDEA and Android Studio.
                      language="kotlin"
     />
 
+    <localInspection implementationClass="org.jetbrains.kotlin.idea.inspections.OptionalExpectationInspection"
+                     displayName="Optionally expected annotation has no actual annotation"
+                     groupPath="Kotlin"
+                     groupName="Style issues"
+                     enabledByDefault="true"
+                     level="INFORMATION"
+                     language="kotlin"
+    />
+
     <referenceImporter implementation="org.jetbrains.kotlin.idea.quickfix.KotlinReferenceImporter"/>
 
     <fileType.fileViewProviderFactory filetype="KJSM" implementationClass="com.intellij.psi.ClassFileViewProviderFactory"/>

idea/src/META-INF/plugin.xml.183

@@ -3057,6 +3057,15 @@ The Kotlin plugin provides language support in IntelliJ IDEA and Android Studio.
                      language="kotlin"
     />
 
+    <localInspection implementationClass="org.jetbrains.kotlin.idea.inspections.OptionalExpectationInspection"
+                     displayName="Optionally expected annotation has no actual annotation"
+                     groupPath="Kotlin"
+                     groupName="Style issues"
+                     enabledByDefault="true"
+                     level="INFORMATION"
+                     language="kotlin"
+    />
+
     <referenceImporter implementation="org.jetbrains.kotlin.idea.quickfix.KotlinReferenceImporter"/>
 
     <fileType.fileViewProviderFactory filetype="KJSM" implementationClass="com.intellij.psi.ClassFileViewProviderFactory"/>

idea/src/META-INF/plugin.xml.as31

@@ -3055,6 +3055,15 @@ The Kotlin plugin provides language support in IntelliJ IDEA and Android Studio.
                      language="kotlin"
     />
 
+    <localInspection implementationClass="org.jetbrains.kotlin.idea.inspections.OptionalExpectationInspection"
+                     displayName="Optionally expected annotation has no actual annotation"
+                     groupPath="Kotlin"
+                     groupName="Style issues"
+                     enabledByDefault="true"
+                     level="INFORMATION"
+                     language="kotlin"
+    />
+
     <referenceImporter implementation="org.jetbrains.kotlin.idea.quickfix.KotlinReferenceImporter"/>
 
     <fileType.fileViewProviderFactory filetype="KJSM" implementationClass="com.intellij.psi.ClassFileViewProviderFactory"/>

idea/src/META-INF/plugin.xml.as32

@@ -3055,6 +3055,15 @@ The Kotlin plugin provides language support in IntelliJ IDEA and Android Studio.
                      language="kotlin"
     />
 
+    <localInspection implementationClass="org.jetbrains.kotlin.idea.inspections.OptionalExpectationInspection"
+                     displayName="Optionally expected annotation has no actual annotation"
+                     groupPath="Kotlin"
+                     groupName="Style issues"
+                     enabledByDefault="true"
+                     level="INFORMATION"
+                     language="kotlin"
+    />
+
     <referenceImporter implementation="org.jetbrains.kotlin.idea.quickfix.KotlinReferenceImporter"/>
 
     <fileType.fileViewProviderFactory filetype="KJSM" implementationClass="com.intellij.psi.ClassFileViewProviderFactory"/>

idea/src/META-INF/plugin.xml.as33

@@ -3057,6 +3057,15 @@ The Kotlin plugin provides language support in IntelliJ IDEA and Android Studio.
                      language="kotlin"
     />
 
+    <localInspection implementationClass="org.jetbrains.kotlin.idea.inspections.OptionalExpectationInspection"
+                     displayName="Optionally expected annotation has no actual annotation"
+                     groupPath="Kotlin"
+                     groupName="Style issues"
+                     enabledByDefault="true"
+                     level="INFORMATION"
+                     language="kotlin"
+    />
+
     <referenceImporter implementation="org.jetbrains.kotlin.idea.quickfix.KotlinReferenceImporter"/>
 
     <fileType.fileViewProviderFactory filetype="KJSM" implementationClass="com.intellij.psi.ClassFileViewProviderFactory"/>

idea/src/org/jetbrains/kotlin/idea/inspections/OptionalExpectationInspection.kt

@@ -0,0 +1,64 @@
+/*
+ * Copyright 2010-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license
+ * that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.idea.inspections
+
+import com.intellij.codeInspection.IntentionWrapper
+import com.intellij.codeInspection.LocalInspectionToolSession
+import com.intellij.codeInspection.ProblemHighlightType
+import com.intellij.codeInspection.ProblemsHolder
+import org.jetbrains.kotlin.analyzer.ModuleInfo
+import org.jetbrains.kotlin.idea.caches.project.ModuleSourceInfo
+import org.jetbrains.kotlin.idea.caches.project.implementingDescriptors
+import org.jetbrains.kotlin.idea.caches.resolve.findModuleDescriptor
+import org.jetbrains.kotlin.idea.caches.resolve.resolveToDescriptorIfAny
+import org.jetbrains.kotlin.idea.quickfix.expectactual.CreateActualClassFix
+import org.jetbrains.kotlin.psi.KtClass
+import org.jetbrains.kotlin.psi.KtClassOrObject
+import org.jetbrains.kotlin.psi.classOrObjectVisitor
+import org.jetbrains.kotlin.psi.psiUtil.hasExpectModifier
+import org.jetbrains.kotlin.resolve.MultiTargetPlatform
+import org.jetbrains.kotlin.resolve.checkers.ExpectedActualDeclarationChecker
+import org.jetbrains.kotlin.resolve.checkers.ExpectedActualDeclarationChecker.allStrongIncompatibilities
+import org.jetbrains.kotlin.resolve.descriptorUtil.module
+import org.jetbrains.kotlin.resolve.getMultiTargetPlatform
+import org.jetbrains.kotlin.resolve.multiplatform.ExpectedActualResolver
+
+class OptionalExpectationInspection : AbstractKotlinInspection() {
+    override fun buildVisitor(holder: ProblemsHolder, isOnTheFly: Boolean, session: LocalInspectionToolSession) =
+        classOrObjectVisitor(fun(classOrObject: KtClassOrObject) {
+            if (classOrObject !is KtClass || !classOrObject.isAnnotation()) return
+            if (!classOrObject.hasExpectModifier()) return
+
+            val descriptor = classOrObject.resolveToDescriptorIfAny() ?: return
+            if (!descriptor.annotations.hasAnnotation(ExpectedActualDeclarationChecker.OPTIONAL_EXPECTATION_FQ_NAME)) return
+
+            val implementingModules = classOrObject.findModuleDescriptor().implementingDescriptors
+            if (implementingModules.isEmpty()) return
+
+            for (actualModuleDescriptor in implementingModules) {
+                val compatibility = ExpectedActualResolver.findActualForExpected(descriptor, actualModuleDescriptor) ?: continue
+                if (!compatibility.allStrongIncompatibilities() &&
+                    (ExpectedActualResolver.Compatibility.Compatible in compatibility ||
+                            !compatibility.values.flatMapTo(
+                                hashSetOf()
+                            ) { it }.all { actual ->
+                                val expectedOnes = ExpectedActualResolver.findExpectedForActual(actual, descriptor.module)
+                                expectedOnes != null && ExpectedActualResolver.Compatibility.Compatible in expectedOnes.keys
+                            })
+                ) continue
+                val platform = (actualModuleDescriptor.getMultiTargetPlatform() as? MultiTargetPlatform.Specific) ?: continue
+                val displayedName = actualModuleDescriptor.getCapability(ModuleInfo.Capability)?.displayedName ?: ""
+                val actualModule = (actualModuleDescriptor.getCapability(ModuleInfo.Capability) as? ModuleSourceInfo)?.module ?: continue
+                holder.registerProblem(
+                    classOrObject.nameIdentifier ?: classOrObject,
+                    "Optionally expected annotation has no actual annotation in module $displayedName for platform ${platform.platform}",
+                    // NB: some highlighting is not suggested for this inspection
+                    ProblemHighlightType.INFORMATION,
+                    IntentionWrapper(CreateActualClassFix(classOrObject, actualModule, platform), classOrObject.containingFile)
+                )
+            }
+        })
+}

idea/src/org/jetbrains/kotlin/idea/quickfix/expectactual/CreateActualFix.kt

@@ -43,10 +43,13 @@ import org.jetbrains.kotlin.idea.util.IdeDescriptorRenderers
 import org.jetbrains.kotlin.idea.util.actualsForExpected
 import org.jetbrains.kotlin.idea.util.application.runWriteAction
 import org.jetbrains.kotlin.lexer.KtTokens
+import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.psi.*
 import org.jetbrains.kotlin.psi.psiUtil.hasExpectModifier
 import org.jetbrains.kotlin.resolve.BindingContext
 import org.jetbrains.kotlin.resolve.MultiTargetPlatform
+import org.jetbrains.kotlin.resolve.checkers.ExpectedActualDeclarationChecker
+import org.jetbrains.kotlin.resolve.checkers.ExperimentalUsageChecker
 import org.jetbrains.kotlin.resolve.getMultiTargetPlatform
 
 sealed class CreateActualFix<out D : KtNamedDeclaration>(
@@ -280,6 +283,14 @@ internal fun KtPsiFactory.generateClassOrObjectByExpectedClass(
             actualEntry.replace(createSuperTypeCallEntry("${actualEntry.typeReference!!.text}()"))
         }
     }
+    if (actualClass.isAnnotation()) {
+        actualClass.annotationEntries.zip(expectedClass.annotationEntries).forEach { (actualEntry, expectedEntry) ->
+            val annotationDescriptor = context.get(BindingContext.ANNOTATION, expectedEntry) ?: return@forEach
+            if (annotationDescriptor.fqName in forbiddenAnnotationFqNames) {
+                actualEntry.delete()
+            }
+        }
+    }
 
     declLoop@ for (expectedDeclaration in expectedClass.declarations.filter { !it.exists() }) {
         val descriptor = expectedDeclaration.toDescriptor() ?: continue
@@ -319,6 +330,12 @@ internal fun KtPsiFactory.generateClassOrObjectByExpectedClass(
     }
 }
 
+private val forbiddenAnnotationFqNames = setOf(
+    ExpectedActualDeclarationChecker.OPTIONAL_EXPECTATION_FQ_NAME,
+    FqName("kotlin.ExperimentalMultiplatform"),
+    ExperimentalUsageChecker.USE_EXPERIMENTAL_FQ_NAME
+)
+
 private fun KtPsiFactory.generateFunction(
     project: Project,
     expectedFunction: KtFunction,