Search for source of platform binary also in common sources

So #KT-20971 Fixed

idea/idea-analysis/src/org/jetbrains/kotlin/idea/decompiler/navigation/SourceNavigationHelper.kt

@@ -19,6 +19,7 @@ import com.intellij.util.containers.ContainerUtil
 import gnu.trove.THashSet
 import org.jetbrains.annotations.TestOnly
 import org.jetbrains.kotlin.descriptors.CallableDescriptor
+import org.jetbrains.kotlin.idea.caches.resolve.BinaryModuleInfo
 import org.jetbrains.kotlin.idea.caches.resolve.getBinaryLibrariesModuleInfos
 import org.jetbrains.kotlin.idea.caches.resolve.getLibrarySourcesModuleInfos
 import org.jetbrains.kotlin.idea.caches.resolve.resolveToDescriptorIfAny
@@ -32,6 +33,7 @@ import org.jetbrains.kotlin.lexer.KtTokens
 import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.psi.*
 import org.jetbrains.kotlin.psi.debugText.getDebugText
+import org.jetbrains.kotlin.resolve.TargetPlatform
 
 object SourceNavigationHelper {
     private val LOG = Logger.getInstance(SourceNavigationHelper::class.java)
@@ -53,8 +55,19 @@ object SourceNavigationHelper {
         val vFile = containingFile.virtualFile ?: return null
 
         return when (navigationKind) {
-            NavigationKind.CLASS_FILES_TO_SOURCES -> getBinaryLibrariesModuleInfos(declaration.project, vFile)
-                .mapNotNull { it.sourcesModuleInfo?.sourceScope() }.union()
+            NavigationKind.CLASS_FILES_TO_SOURCES -> {
+                val binaryModuleInfos = getBinaryLibrariesModuleInfos(declaration.project, vFile)
+                binaryModuleInfos.map { binaryModuleInfo ->
+                    val platform = binaryModuleInfo.platform
+                    if (platform == null || platform == TargetPlatform.Common) {
+                        listOf(binaryModuleInfo)
+                    } else {
+                        binaryModuleInfo.dependencies().filterIsInstance<BinaryModuleInfo>().filter {
+                            it.platform == TargetPlatform.Common
+                        } + binaryModuleInfo
+                    }
+                }.flatten().mapNotNull { it.sourcesModuleInfo?.sourceScope() }.union()
+            }
 
             NavigationKind.SOURCES_TO_CLASS_FILES -> getLibrarySourcesModuleInfos(declaration.project, vFile)
                 .map { it.binariesModuleInfo.binariesScope() }.union()