[fir2ir] Generate facade stubs for external source declarations

In the IDE, it's impossible to pass classes from all modules to the
backend, so symbols for 'external' source declarations need to be
generated ad-hoc.

Such declarations do not go through the lowering phase, including one
that replaces the containing package fragment with a facade class.

compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/Fir2IrDeclarationStorage.kt

@@ -8,6 +8,7 @@ package org.jetbrains.kotlin.fir.backend
 import org.jetbrains.kotlin.KtFakeSourceElementKind
 import org.jetbrains.kotlin.builtins.StandardNames.BUILT_INS_PACKAGE_FQ_NAMES
 import org.jetbrains.kotlin.descriptors.*
+import org.jetbrains.kotlin.fileClasses.JvmFileClassUtil
 import org.jetbrains.kotlin.fir.*
 import org.jetbrains.kotlin.fir.declarations.*
 import org.jetbrains.kotlin.fir.declarations.builder.buildProperty
@@ -42,10 +43,7 @@ import org.jetbrains.kotlin.ir.UNDEFINED_OFFSET
 import org.jetbrains.kotlin.ir.builders.declarations.UNDEFINED_PARAMETER_INDEX
 import org.jetbrains.kotlin.ir.declarations.*
 import org.jetbrains.kotlin.ir.declarations.IrDeclarationOrigin.GeneratedByPlugin
-import org.jetbrains.kotlin.ir.declarations.impl.IrExternalPackageFragmentImpl
+import org.jetbrains.kotlin.ir.declarations.impl.*
-import org.jetbrains.kotlin.ir.declarations.impl.IrScriptImpl
-import org.jetbrains.kotlin.ir.declarations.impl.IrVariableImpl
-import org.jetbrains.kotlin.ir.declarations.impl.SCRIPT_K2_ORIGIN
 import org.jetbrains.kotlin.ir.declarations.lazy.IrLazyClass
 import org.jetbrains.kotlin.ir.expressions.IrExpression
 import org.jetbrains.kotlin.ir.expressions.IrSyntheticBodyKind
@@ -55,10 +53,15 @@ import org.jetbrains.kotlin.ir.symbols.impl.*
 import org.jetbrains.kotlin.ir.types.IrSimpleType
 import org.jetbrains.kotlin.ir.types.IrType
 import org.jetbrains.kotlin.ir.util.*
+import org.jetbrains.kotlin.load.kotlin.FacadeClassSource
 import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.name.NameUtils
 import org.jetbrains.kotlin.name.SpecialNames
+import org.jetbrains.kotlin.psi.KtFile
+import org.jetbrains.kotlin.resolve.jvm.JvmClassName
+import org.jetbrains.kotlin.serialization.deserialization.descriptors.DeserializedContainerAbiStability
+import org.jetbrains.kotlin.serialization.deserialization.descriptors.DeserializedContainerSource
 import org.jetbrains.kotlin.utils.addToStdlib.runUnless
 import org.jetbrains.kotlin.utils.exceptions.errorWithAttachment
 import org.jetbrains.kotlin.utils.threadLocal
@@ -294,23 +297,94 @@ class Fir2IrDeclarationStorage(
         firBasedSymbol: FirBasedSymbol<*>,
         firOrigin: FirDeclarationOrigin
     ): IrDeclarationParent? {
-        return if (parentLookupTag != null) {
+        if (parentLookupTag != null) {
-            classifierStorage.findIrClass(parentLookupTag)
+            return classifierStorage.findIrClass(parentLookupTag)
-        } else {
+        }
-            val containerFile = when (firBasedSymbol) {
-                is FirCallableSymbol -> firProvider.getFirCallableContainerFile(firBasedSymbol)
-                is FirClassLikeSymbol -> firProvider.getFirClassifierContainerFileIfAny(firBasedSymbol)
-                else -> error("Unknown symbol: $firBasedSymbol")
-            }
 
-            when {
+        val parentPackage = when (firBasedSymbol) {
-                containerFile != null -> fileCache[containerFile]
+            is FirCallableSymbol<*> -> {
-                firBasedSymbol is FirCallableSymbol -> getIrExternalPackageFragment(packageFqName, firOrigin)
+                getIrExternalPackageFragment(packageFqName, firOrigin)
+            }
+            else -> {
                 // TODO: All classes from BUILT_INS_PACKAGE_FQ_NAMES are considered built-ins now,
                 // which is not exact and can lead to some problems
-                else -> getIrExternalOrBuiltInsPackageFragment(packageFqName, firOrigin)
+                getIrExternalOrBuiltInsPackageFragment(packageFqName, firOrigin)
             }
         }
+
+        val firProviderForSymbol = firBasedSymbol.moduleData.session.firProvider
+        val containerFile = when (firBasedSymbol) {
+            is FirCallableSymbol -> firProviderForSymbol.getFirCallableContainerFile(firBasedSymbol)
+            is FirClassLikeSymbol -> firProviderForSymbol.getFirClassifierContainerFileIfAny(firBasedSymbol)
+            else -> error("Unknown symbol: $firBasedSymbol")
+        }
+
+        if (containerFile != null) {
+            val existingFile = fileCache[containerFile]
+            if (existingFile != null) {
+                return existingFile
+            }
+
+            // Sudden declarations do not go through IR lowering process,
+            // so the parent file isn't replaced with a facade class, as in 'FileClassLowering'.
+            if (configuration.allowNonCachedDeclarations && firBasedSymbol is FirCallableSymbol<*>) {
+                val psiFile = containerFile.psi?.containingFile
+                if (psiFile is KtFile) {
+                    val fileClassInfo = JvmFileClassUtil.getFileClassInfoNoResolve(psiFile)
+                    val className = JvmClassName.byFqNameWithoutInnerClasses(fileClassInfo.fileClassFqName)
+
+                    val facadeClassName: JvmClassName?
+                    val declarationOrigin: IrDeclarationOrigin
+
+                    if (fileClassInfo.withJvmMultifileClass) {
+                        facadeClassName = JvmClassName.byFqNameWithoutInnerClasses(fileClassInfo.facadeClassFqName)
+                        declarationOrigin = IrDeclarationOrigin.JVM_MULTIFILE_CLASS
+                    } else {
+                        facadeClassName = null
+                        declarationOrigin = IrDeclarationOrigin.FILE_CLASS
+                    }
+
+                    val facadeShortName = className.fqNameForClassNameWithoutDollars.shortName()
+                    val containerSource = NonCachedSourceFacadeContainerSource(className, facadeClassName)
+                    return NonCachedSourceFileFacadeClass(declarationOrigin, facadeShortName, containerSource).apply {
+                        parent = parentPackage
+                        createParameterDeclarations()
+                    }
+                }
+            }
+        }
+
+        return parentPackage
+    }
+
+    private class NonCachedSourceFileFacadeClass(
+        origin: IrDeclarationOrigin,
+        name: Name,
+        source: SourceElement,
+    ) : IrClassImpl(
+        UNDEFINED_OFFSET, UNDEFINED_OFFSET, origin, IrClassSymbolImpl(), name,
+        ClassKind.CLASS, DescriptorVisibilities.PUBLIC, Modality.FINAL,
+        source = source
+    )
+
+    private class NonCachedSourceFacadeContainerSource(
+        override val className: JvmClassName,
+        override val facadeClassName: JvmClassName?
+    ) : DeserializedContainerSource, FacadeClassSource {
+        override val incompatibility get() = null
+        override val isPreReleaseInvisible get() = false
+        override val abiStability get() = DeserializedContainerAbiStability.STABLE
+        override val presentableString get() = className.internalName
+
+        override fun getContainingFile(): SourceFile = SourceFile.NO_SOURCE_FILE
+    }
+
+    private fun computeThisReceiverOwner(parent: IrDeclarationParent?): IrClass? {
+        if (parent is IrClass && parent !is NonCachedSourceFileFacadeClass) {
+            return parent
+        }
+
+        return null
     }
 
     internal fun findIrParent(callableDeclaration: FirCallableDeclaration): IrDeclarationParent? {
@@ -462,7 +536,7 @@ class Fir2IrDeclarationStorage(
     private fun <T : IrFunction> T.bindAndDeclareParameters(
         function: FirFunction?,
         irParent: IrDeclarationParent?,
-        thisReceiverOwner: IrClass? = irParent as? IrClass,
+        thisReceiverOwner: IrClass?,
         isStatic: Boolean,
         forSetter: Boolean,
         parentPropertyReceiver: FirReceiverParameter? = null
@@ -540,7 +614,7 @@ class Fir2IrDeclarationStorage(
     fun createIrFunction(
         function: FirFunction,
         irParent: IrDeclarationParent?,
-        thisReceiverOwner: IrClass? = irParent as? IrClass,
+        thisReceiverOwner: IrClass? = computeThisReceiverOwner(irParent),
         predefinedOrigin: IrDeclarationOrigin? = null,
         isLocal: Boolean = false,
         fakeOverrideOwnerLookupTag: ConeClassLikeLookupTag? = null,
@@ -707,7 +781,7 @@ class Fir2IrDeclarationStorage(
                     // with the annotation itself.
                     constructorCache[constructor] = this
                     enterScope(this)
-                    bindAndDeclareParameters(constructor, irParent, isStatic = false, forSetter = false)
+                    bindAndDeclareParameters(constructor, irParent, irParent, isStatic = false, forSetter = false)
                     leaveScope(this)
                 }
             }
@@ -739,7 +813,7 @@ class Fir2IrDeclarationStorage(
         correspondingProperty: IrDeclarationWithName,
         propertyType: IrType,
         irParent: IrDeclarationParent?,
-        thisReceiverOwner: IrClass? = irParent as? IrClass,
+        thisReceiverOwner: IrClass? = computeThisReceiverOwner(irParent),
         isSetter: Boolean,
         origin: IrDeclarationOrigin,
         startOffset: Int,
@@ -924,7 +998,7 @@ class Fir2IrDeclarationStorage(
     fun createIrProperty(
         property: FirProperty,
         irParent: IrDeclarationParent?,
-        thisReceiverOwner: IrClass? = irParent as? IrClass,
+        thisReceiverOwner: IrClass? = computeThisReceiverOwner(irParent),
         predefinedOrigin: IrDeclarationOrigin? = null,
         isLocal: Boolean = false,
         fakeOverrideOwnerLookupTag: ConeClassLikeLookupTag? = (irParent as? IrClass)?.classId?.toLookupTag(),