KT-11410: generate light classes from multifile class parts in binaries

if explicitly requested by fqName

compiler/cli/src/org/jetbrains/kotlin/cli/jvm/compiler/CliLightClassGenerationSupport.kt

@@ -149,6 +149,11 @@ class CliLightClassGenerationSupport(project: Project) : LightClassGenerationSup
                 KtLightClassForFacade.createForFacade(psiManager, facadeFqName, scope, filesForFacade))
     }
 
+    override fun getMultifilePartClasses(partFqName: FqName, scope: GlobalSearchScope): Collection<PsiClass> {
+        //
+        return emptyList()
+    }
+
     override fun findFilesForFacade(facadeFqName: FqName, scope: GlobalSearchScope): Collection<KtFile> {
         if (facadeFqName.isRoot) return emptyList()
 

compiler/light-classes/src/org/jetbrains/kotlin/asJava/JavaElementFinder.java

@@ -92,6 +92,7 @@ public class JavaElementFinder extends PsiElementFinder implements KotlinFinderM
         findClassesAndObjects(qualifiedName, scope, answer);
 
         answer.addAll(lightClassGenerationSupport.getFacadeClasses(qualifiedName, scope));
+        answer.addAll(lightClassGenerationSupport.getMultifilePartClasses(qualifiedName, scope));
 
         return sortByClasspath(answer, scope).toArray(new PsiClass[answer.size()]);
     }

compiler/light-classes/src/org/jetbrains/kotlin/asJava/LightClassGenerationSupport.java

@@ -75,6 +75,9 @@ public abstract class LightClassGenerationSupport {
     @NotNull
     public abstract Collection<PsiClass> getFacadeClasses(@NotNull FqName facadeFqName, @NotNull GlobalSearchScope scope);
 
+    @NotNull
+    public abstract Collection<PsiClass> getMultifilePartClasses(@NotNull FqName partFqName, @NotNull GlobalSearchScope scope);
+
     @NotNull
     public abstract Collection<PsiClass> getFacadeClassesInPackage(@NotNull FqName packageFqName, @NotNull GlobalSearchScope scope);
 
@@ -86,5 +89,4 @@ public abstract class LightClassGenerationSupport {
 
     @NotNull
     public abstract LightClassConstructionContext getContextForFacade(@NotNull Collection<KtFile> files);
-
 }

idea/idea-analysis/src/org/jetbrains/kotlin/idea/caches/resolve/IDELightClassGenerationSupport.kt

@@ -174,6 +174,24 @@ class IDELightClassGenerationSupport(private val project: Project) : LightClassG
         }
     }
 
+    override fun getMultifilePartClasses(partFqName: FqName, scope: GlobalSearchScope): Collection<PsiClass> {
+        val facadeKtFiles = StaticFacadeIndexUtil.getMultifileClassForPart(partFqName, scope, project)
+        val partShortName = partFqName.shortName().asString()
+        val partClassFileShortName = partShortName + ".class"
+
+        return facadeKtFiles.mapNotNull { facadeKtFile ->
+            if (facadeKtFile is KtClsFile) {
+                val partClassFile = facadeKtFile.virtualFile.parent.findChild(partClassFileShortName) ?: return@mapNotNull null
+                val javaClsClass = createClsJavaClassFromVirtualFile(facadeKtFile, partClassFile, null) ?: return@mapNotNull null
+                KtLightClassForDecompiledDeclaration(javaClsClass, null, facadeKtFile)
+            }
+            else {
+                // TODO should we build light classes for parts from source?
+                null
+            }
+        }
+    }
+
     fun createLightClassForFileFacade(
             facadeFqName: FqName,
             facadeFiles: List<KtFile>,