Add explicit return type check for API mode

It will use the same SpecifyTypeExplicitlyIntention as in other places; to reuse check logic, some parts of code were moved from corresponding inspection (PublicApiImplicitTypeInspection) into ApiModeDeclarationChecker.

Also disable RedundantVisibilityModifierInspection when API mode is on.

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

@@ -6,13 +6,12 @@
 package org.jetbrains.kotlin.idea.inspections
 
 import com.intellij.codeInspection.ui.MultipleCheckboxOptionsPanel
+import org.jetbrains.kotlin.config.AnalysisFlags
+import org.jetbrains.kotlin.config.ApiMode
 import org.jetbrains.kotlin.descriptors.CallableMemberDescriptor
-import org.jetbrains.kotlin.descriptors.Visibilities
-import org.jetbrains.kotlin.descriptors.effectiveVisibility
 import org.jetbrains.kotlin.idea.caches.resolve.resolveToDescriptorIfAny
-import org.jetbrains.kotlin.psi.KtFunction
-import org.jetbrains.kotlin.psi.KtProperty
-import org.jetbrains.kotlin.psi.psiUtil.containingClassOrObject
+import org.jetbrains.kotlin.idea.project.languageVersionSettings
+import org.jetbrains.kotlin.resolve.checkers.ApiModeDeclarationChecker
 import javax.swing.JComponent
 
 class PublicApiImplicitTypeInspection(
@@ -20,20 +19,11 @@ class PublicApiImplicitTypeInspection(
     @JvmField var reportPrivate: Boolean = false
 ) : AbstractImplicitTypeInspection(
     { element, inspection ->
-        element.containingClassOrObject?.isLocal != true &&
-                when (element) {
-                    is KtFunction -> !element.isLocal
-                    is KtProperty -> !element.isLocal
-                    else -> false
-                } && run {
-            val callableMemberDescriptor = element.resolveToDescriptorIfAny() as? CallableMemberDescriptor
-            val forInternal = (inspection as PublicApiImplicitTypeInspection).reportInternal
-            val forPrivate = inspection.reportPrivate
-
-            val visibility = callableMemberDescriptor?.effectiveVisibility()?.toVisibility()
-            visibility?.isPublicAPI == true || (forInternal && visibility == Visibilities.INTERNAL) ||
-                    (forPrivate && visibility == Visibilities.PRIVATE)
-        }
+        val shouldCheckForPublic = element.languageVersionSettings.getFlag(AnalysisFlags.apiMode) == ApiMode.DISABLED
+        val callableMemberDescriptor = element.resolveToDescriptorIfAny() as? CallableMemberDescriptor
+        val forInternal = (inspection as PublicApiImplicitTypeInspection).reportInternal
+        val forPrivate = inspection.reportPrivate
+        ApiModeDeclarationChecker.returnTypeRequired(element, callableMemberDescriptor, shouldCheckForPublic, forInternal, forPrivate)
     }
 ) {
 

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

@@ -7,11 +7,14 @@ package org.jetbrains.kotlin.idea.inspections
 
 import com.intellij.codeInspection.*
 import com.intellij.psi.PsiElementVisitor
+import org.jetbrains.kotlin.config.AnalysisFlags
+import org.jetbrains.kotlin.config.ApiMode
 import org.jetbrains.kotlin.descriptors.CallableMemberDescriptor
 import org.jetbrains.kotlin.descriptors.PropertyDescriptor
 import org.jetbrains.kotlin.descriptors.Visibilities
 import org.jetbrains.kotlin.descriptors.Visibility
 import org.jetbrains.kotlin.idea.core.implicitVisibility
+import org.jetbrains.kotlin.idea.project.languageVersionSettings
 import org.jetbrains.kotlin.idea.quickfix.RemoveModifierFix
 import org.jetbrains.kotlin.idea.search.usagesSearch.descriptor
 import org.jetbrains.kotlin.lexer.KtTokens
@@ -26,6 +29,9 @@ import org.jetbrains.kotlin.utils.addToStdlib.firstNotNullResult
 class RedundantVisibilityModifierInspection : AbstractKotlinInspection(), CleanupLocalInspectionTool {
     override fun buildVisitor(holder: ProblemsHolder, isOnTheFly: Boolean, session: LocalInspectionToolSession): PsiElementVisitor {
         return declarationVisitor(fun(declaration: KtDeclaration) {
+            val isInApiMode = declaration.languageVersionSettings.getFlag(AnalysisFlags.apiMode) != ApiMode.DISABLED
+            if (isInApiMode) return@declarationVisitor
+
             if (declaration is KtPropertyAccessor && declaration.isGetter) return // There is a quick fix for REDUNDANT_MODIFIER_IN_GETTER
             val visibilityModifier = declaration.visibilityModifier() ?: return
             val implicitVisibility = declaration.implicitVisibility()

idea/src/org/jetbrains/kotlin/idea/intentions/SpecifyTypeExplicitlyIntention.kt

@@ -39,6 +39,7 @@ import org.jetbrains.kotlin.idea.util.getResolvableApproximations
 import org.jetbrains.kotlin.psi.*
 import org.jetbrains.kotlin.psi.psiUtil.*
 import org.jetbrains.kotlin.resolve.DescriptorToSourceUtils
+import org.jetbrains.kotlin.resolve.checkers.ApiModeDeclarationChecker
 import org.jetbrains.kotlin.resolve.lazy.BodyResolveMode
 import org.jetbrains.kotlin.types.*
 import org.jetbrains.kotlin.types.typeUtil.makeNotNullable
@@ -50,12 +51,7 @@ class SpecifyTypeExplicitlyIntention : SelfTargetingRangeIntention<KtCallableDec
 ), HighPriorityAction {
 
     override fun applicabilityRange(element: KtCallableDeclaration): TextRange? {
-        if (element.containingFile is KtCodeFragment) return null
-        if (element is KtFunctionLiteral) return null // TODO: should KtFunctionLiteral be KtCallableDeclaration at all?
-        if (element is KtConstructor<*>) return null
-        if (element.typeReference != null) return null
-
-        if (element is KtNamedFunction && element.hasBlockBody()) return null
+        if (!ApiModeDeclarationChecker.returnTypeCheckIsApplicable(element)) return null
 
         text = if (element is KtFunction) "Specify return type explicitly" else "Specify type explicitly"
 

idea/src/org/jetbrains/kotlin/idea/quickfix/QuickFixRegistrar.kt

@@ -25,10 +25,7 @@ import org.jetbrains.kotlin.idea.inspections.AddModifierFixFactory
 import org.jetbrains.kotlin.idea.inspections.InfixCallFixActionFactory
 import org.jetbrains.kotlin.idea.inspections.PlatformUnresolvedProvider
 import org.jetbrains.kotlin.idea.inspections.RemoveAnnotationFix
-import org.jetbrains.kotlin.idea.intentions.AbstractAddAccessorsIntention
-import org.jetbrains.kotlin.idea.intentions.AddValVarToConstructorParameterAction
-import org.jetbrains.kotlin.idea.intentions.ConvertPropertyInitializerToGetterIntention
-import org.jetbrains.kotlin.idea.intentions.MoveMemberToCompanionObjectIntention
+import org.jetbrains.kotlin.idea.intentions.*
 import org.jetbrains.kotlin.idea.quickfix.createFromUsage.createCallable.*
 import org.jetbrains.kotlin.idea.quickfix.createFromUsage.createClass.CreateClassFromCallWithConstructorCalleeActionFactory
 import org.jetbrains.kotlin.idea.quickfix.createFromUsage.createClass.CreateClassFromConstructorCallActionFactory
@@ -154,6 +151,9 @@ class QuickFixRegistrar : QuickFixContributor {
         FORBIDDEN_BINARY_MOD.registerFactory(removeModifierFactory)
         FORBIDDEN_BINARY_MOD.registerFactory(RenameModToRemFix.Factory)
 
+        NO_EXPLICIT_RETURN_TYPE_IN_API_MODE.registerActions(SpecifyTypeExplicitlyFix())
+        NO_EXPLICIT_RETURN_TYPE_IN_API_MODE_MIGRATION.registerActions(SpecifyTypeExplicitlyFix())
+
 
         UNRESOLVED_REFERENCE.registerFactory(ImportFix)
         UNRESOLVED_REFERENCE.registerFactory(ImportConstructorReferenceFix)