Show expect / actual gutter even for incomplete compatibility

So #KT-18445 Fixed
So #KT-21115 Fixed

idea/src/org/jetbrains/kotlin/idea/highlighter/markers/HasActualMarker.kt

@@ -35,7 +35,7 @@ import java.awt.event.MouseEvent
 fun ModuleDescriptor.hasActualsFor(descriptor: MemberDescriptor) =
         actualsFor(descriptor).isNotEmpty()
 
-fun ModuleDescriptor.actualsFor(descriptor: MemberDescriptor, checkCompatible: Boolean = true): List<DeclarationDescriptor> =
+fun ModuleDescriptor.actualsFor(descriptor: MemberDescriptor, checkCompatible: Boolean = false): List<DeclarationDescriptor> =
         with(ExpectedActualResolver) {
             if (checkCompatible) {
                 descriptor.findCompatibleActualForExpected(this@actualsFor)

idea/src/org/jetbrains/kotlin/idea/highlighter/markers/HasExpectedMarker.kt

@@ -29,14 +29,16 @@ import org.jetbrains.kotlin.psi.psiUtil.hasExpectModifier
 import org.jetbrains.kotlin.resolve.DescriptorToSourceUtils
 import org.jetbrains.kotlin.resolve.descriptorUtil.module
 import org.jetbrains.kotlin.resolve.multiplatform.ExpectedActualResolver
+import org.jetbrains.kotlin.resolve.multiplatform.ExpectedActualResolver.Compatibility.*
 import org.jetbrains.kotlin.utils.addToStdlib.safeAs
 
 fun ModuleDescriptor.hasDeclarationOf(descriptor: MemberDescriptor) = declarationOf(descriptor) != null
 
 private fun ModuleDescriptor.declarationOf(descriptor: MemberDescriptor): DeclarationDescriptor? =
-        with(ExpectedActualResolver) {
+    with(ExpectedActualResolver) {
-            descriptor.findCompatibleExpectedForActual(this@declarationOf).firstOrNull()
+        val expectedCompatibilityMap = findExpectedForActual(descriptor, this@declarationOf)
-        }
+        expectedCompatibilityMap?.get(Compatible)?.firstOrNull() ?: expectedCompatibilityMap?.values?.flatten()?.firstOrNull()
+    }
 
 fun getExpectedDeclarationTooltip(declaration: KtDeclaration?): String? {
     val descriptor = declaration?.toDescriptor() as? MemberDescriptor ?: return null
@@ -67,8 +69,7 @@ internal fun KtDeclaration.isExpectedOrExpectedClassMember(): Boolean {
 }
 
 internal fun KtClassOrObject.isExpected(): Boolean {
-    return this.hasExpectModifier() ||
+    return this.hasExpectModifier() || this.descriptor.safeAs<ClassDescriptor>()?.isExpect == true
-           this.descriptor.safeAs<ClassDescriptor>()?.isExpect == true
 }
 
 internal fun DeclarationDescriptor.liftToExpected(): DeclarationDescriptor? {

idea/testData/multiModuleLineMarker/fromCommonToJvmHeader/common/common.kt

@@ -2,6 +2,10 @@ expect class <lineMarker>Header</lineMarker> {
     fun <lineMarker>foo</lineMarker>(): Int
 }
 
+expect class <lineMarker>Incomplete</lineMarker> {
+    fun foo(): Int
+}
+
 expect fun <lineMarker>foo</lineMarker>(arg: Int): String
 
 expect val <lineMarker>flag</lineMarker>: Boolean

idea/testData/multiModuleLineMarker/fromCommonToJvmHeader/jvm/jvm.kt

@@ -4,6 +4,8 @@ actual class Header {
     actual fun foo() = 42
 }
 
+actual class Incomplete
+
 actual fun foo(arg: Int) = arg.toString()
 
 actual val flag = true

idea/testData/multiModuleLineMarker/fromCommonToJvmImpl/common/common.kt

@@ -4,6 +4,10 @@ expect class Header {
     fun foo(): Int
 }
 
+expect class Incomplete {
+    fun foo(): Int
+}
+
 expect fun foo(arg: Int): String
 
 expect val flag: Boolean

idea/testData/multiModuleLineMarker/fromCommonToJvmImpl/jvm/jvm.kt

@@ -2,6 +2,8 @@ actual class <lineMarker>Header</lineMarker> {
     actual fun <lineMarker>foo</lineMarker>() = 42
 }
 
+actual class <lineMarker>Incomplete</lineMarker>
+
 actual fun <lineMarker>foo</lineMarker>(arg: Int) = arg.toString()
 
 actual val <lineMarker>flag</lineMarker> = true