[Test] Reproduce crash when plugin generates top-level private suspend

...function.

^KT-61993

plugins/fir-plugin-prototype/plugin-annotations/src/commonMain/kotlin/org/jetbrains/kotlin/fir/plugin/annotations.kt

@@ -11,6 +11,9 @@ annotation class AllOpen
 annotation class AllOpen2
 
 annotation class DummyFunction
+
+@Target(AnnotationTarget.FUNCTION)
+annotation class TestTopLevelPrivateSuspendFun
 annotation class ExternalClassWithNested
 annotation class NestedClassAndMaterializeMember
 annotation class MyInterfaceSupertype

plugins/fir-plugin-prototype/src/org/jetbrains/kotlin/fir/plugin/FirPluginPrototypeExtensionRegistrar.kt

@@ -30,6 +30,7 @@ class FirPluginPrototypeExtensionRegistrar : FirExtensionRegistrar() {
 
         // Declaration generators
         +::TopLevelDeclarationsGenerator
+        +::TopLevelPrivateSuspendFunctionGenerator
         +::ExternalClassGenerator
         +::AdditionalMembersGenerator
         +::CompanionGenerator

plugins/fir-plugin-prototype/src/org/jetbrains/kotlin/fir/plugin/generators/TopLevelPrivateSuspendFunctionGenerator.kt

@@ -0,0 +1,61 @@
+/*
+ * Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.fir.plugin.generators
+
+import org.jetbrains.kotlin.GeneratedDeclarationKey
+import org.jetbrains.kotlin.descriptors.Visibilities
+import org.jetbrains.kotlin.fir.FirSession
+import org.jetbrains.kotlin.fir.extensions.FirDeclarationGenerationExtension
+import org.jetbrains.kotlin.fir.extensions.FirDeclarationPredicateRegistrar
+import org.jetbrains.kotlin.fir.extensions.MemberGenerationContext
+import org.jetbrains.kotlin.fir.extensions.predicate.LookupPredicate
+import org.jetbrains.kotlin.fir.extensions.predicateBasedProvider
+import org.jetbrains.kotlin.fir.plugin.createTopLevelFunction
+import org.jetbrains.kotlin.fir.plugin.fqn
+import org.jetbrains.kotlin.fir.symbols.impl.FirNamedFunctionSymbol
+import org.jetbrains.kotlin.name.CallableId
+import org.jetbrains.kotlin.name.Name
+
+/*
+ * Generates `private suspend fun testFun_generated() {}` function
+ * for each package containing function annotated with `org.jetbrains.kotlin.fir.plugin.TestTopLevelPrivateSuspendFun`.
+ */
+internal class TopLevelPrivateSuspendFunctionGenerator(session: FirSession) : FirDeclarationGenerationExtension(session) {
+    private companion object {
+        private val PREDICATE = LookupPredicate.create { annotated("TestTopLevelPrivateSuspendFun".fqn()) }
+        private val TEST_FUN_NAME = Name.identifier("testFun_generated")
+    }
+
+    private val predicateBasedProvider = session.predicateBasedProvider
+    private val matchedPackageNames by lazy {
+        // This could be done more elegantly if TestTopLevelPrivateSuspendFun was file-level annotation,
+        // but it's currently not possible to find all annotated files using FirPredicateBasedProvider (see KT-66151).
+        predicateBasedProvider.getSymbolsByPredicate(PREDICATE)
+            .filterIsInstance<FirNamedFunctionSymbol>()
+            .map { it.callableId.packageName }
+            .toSet()
+    }
+
+    override fun generateFunctions(callableId: CallableId, context: MemberGenerationContext?): List<FirNamedFunctionSymbol> {
+        if (context != null) return emptyList()
+        if (callableId.callableName != TEST_FUN_NAME) return emptyList()
+        val function = createTopLevelFunction(Key, callableId, session.builtinTypes.unitType.type) {
+            visibility = Visibilities.Private
+            status { isSuspend = true }
+        }
+        return listOf(function.symbol)
+    }
+
+    override fun getTopLevelCallableIds(): Set<CallableId> {
+        return matchedPackageNames.map { CallableId(it, TEST_FUN_NAME) }.toSet()
+    }
+
+    object Key : GeneratedDeclarationKey()
+
+    override fun FirDeclarationPredicateRegistrar.registerPredicates() {
+        register(PREDICATE)
+    }
+}

plugins/fir-plugin-prototype/src/org/jetbrains/kotlin/ir/plugin/GeneratedDeclarationsIrBodyFiller.kt

@@ -17,6 +17,7 @@ class GeneratedDeclarationsIrBodyFiller : IrGenerationExtension {
             TransformerForCompanionGenerator(pluginContext),
             TransformerForAdditionalMembersGenerator(pluginContext),
             TransformerForTopLevelDeclarationsGenerator(pluginContext),
+            TransformerForTopLevelPrivateSuspendFunctionsGenerator(pluginContext),
             AllPropertiesConstructorIrGenerator(pluginContext),
             TransformerForAddingAnnotations(pluginContext),
             ComposableFunctionsTransformer(pluginContext),

plugins/fir-plugin-prototype/src/org/jetbrains/kotlin/ir/plugin/TransformerForTopLevelPrivateSuspendFunctionsGenerator.kt

@@ -0,0 +1,28 @@
+/*
+ * Copyright 2010-2021 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.ir.plugin
+
+import org.jetbrains.kotlin.GeneratedDeclarationKey
+import org.jetbrains.kotlin.backend.common.extensions.IrPluginContext
+import org.jetbrains.kotlin.fir.plugin.generators.TopLevelPrivateSuspendFunctionGenerator
+import org.jetbrains.kotlin.ir.UNDEFINED_OFFSET
+import org.jetbrains.kotlin.ir.declarations.IrConstructor
+import org.jetbrains.kotlin.ir.declarations.IrSimpleFunction
+import org.jetbrains.kotlin.ir.expressions.IrBody
+
+internal class TransformerForTopLevelPrivateSuspendFunctionsGenerator(context: IrPluginContext) : AbstractTransformerForGenerator(context, visitBodies = false) {
+    override fun interestedIn(key: GeneratedDeclarationKey?): Boolean {
+        return key == TopLevelPrivateSuspendFunctionGenerator.Key
+    }
+
+    override fun generateBodyForFunction(function: IrSimpleFunction, key: GeneratedDeclarationKey?): IrBody {
+        return irFactory.createBlockBody(UNDEFINED_OFFSET, UNDEFINED_OFFSET)
+    }
+
+    override fun generateBodyForConstructor(constructor: IrConstructor, key: GeneratedDeclarationKey?): IrBody? {
+        error("Should not be called")
+    }
+}

plugins/fir-plugin-prototype/testData/box/topLevelPrivateSuspendFun.fir.txt

@@ -0,0 +1,10 @@
+FILE: topLevelPrivateSuspendFun.kt
+    package foo
+
+    @R|org/jetbrains/kotlin/fir/plugin/TestTopLevelPrivateSuspendFun|() public final fun box(): R|kotlin/String| {
+        ^box String(OK)
+    }
+FILE: __GENERATED DECLARATIONS__.kt
+    package foo
+
+    private final suspend fun testFun_generated(): R|kotlin/Unit|

plugins/fir-plugin-prototype/testData/box/topLevelPrivateSuspendFun.kt

@@ -0,0 +1,5 @@
+// This test currently fails!
+package foo
+
+@org.jetbrains.kotlin.fir.plugin.TestTopLevelPrivateSuspendFun
+fun box(): String = "OK"

plugins/fir-plugin-prototype/tests-gen/org/jetbrains/kotlin/fir/plugin/runners/FirLightTreePluginBlackBoxCodegenTestGenerated.java

@@ -143,4 +143,10 @@ public class FirLightTreePluginBlackBoxCodegenTestGenerated extends AbstractFirL
   public void testTopLevelCallables() {
     runTest("plugins/fir-plugin-prototype/testData/box/topLevelCallables.kt");
   }
+
+  @Test
+  @TestMetadata("topLevelPrivateSuspendFun.kt")
+  public void testTopLevelPrivateSuspendFun() {
+    runTest("plugins/fir-plugin-prototype/testData/box/topLevelPrivateSuspendFun.kt");
+  }
 }