JVM_IR: improve scope detection in accessor generation.

* Sometimes, there's a class after the last function in the scope
   stack: that's the local type's (non-inline) primary constructor.

 * In an inline (but not crossinline) lambda, accessors are needed
   if and only if they would be needed in the function that the
   lambda is defined in.

compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/lower/CallableReferenceLowering.kt

@@ -7,6 +7,7 @@ package org.jetbrains.kotlin.backend.jvm.lower
 
 import org.jetbrains.kotlin.backend.common.FileLoweringPass
 import org.jetbrains.kotlin.backend.common.IrElementTransformerVoidWithContext
+import org.jetbrains.kotlin.backend.common.IrElementVisitorVoidWithContext
 import org.jetbrains.kotlin.backend.common.ir.copyTo
 import org.jetbrains.kotlin.backend.common.ir.createImplicitParameterDeclarationWithWrappedDescriptor
 import org.jetbrains.kotlin.backend.common.lower.createIrBuilder
@@ -20,6 +21,7 @@ import org.jetbrains.kotlin.backend.jvm.ir.irArray
 import org.jetbrains.kotlin.backend.jvm.ir.isInlineParameter
 import org.jetbrains.kotlin.descriptors.Modality
 import org.jetbrains.kotlin.descriptors.Visibilities
+import org.jetbrains.kotlin.ir.IrElement
 import org.jetbrains.kotlin.ir.IrStatement
 import org.jetbrains.kotlin.ir.builders.*
 import org.jetbrains.kotlin.ir.builders.declarations.addConstructor
@@ -33,10 +35,10 @@ import org.jetbrains.kotlin.ir.expressions.impl.IrInstanceInitializerCallImpl
 import org.jetbrains.kotlin.ir.types.*
 import org.jetbrains.kotlin.ir.util.*
 import org.jetbrains.kotlin.ir.visitors.IrElementTransformerVoid
+import org.jetbrains.kotlin.ir.visitors.acceptChildrenVoid
 import org.jetbrains.kotlin.ir.visitors.transformChildrenVoid
 import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.resolve.DescriptorUtils
-import org.jetbrains.kotlin.utils.addIfNotNull
 
 internal val callableReferencePhase = makeIrFilePhase(
     ::CallableReferenceLowering,
@@ -44,18 +46,19 @@ internal val callableReferencePhase = makeIrFilePhase(
     description = "Handle callable references"
 )
 
-// Originally copied from K/Native
-internal class CallableReferenceLowering(private val context: JvmBackendContext) : FileLoweringPass, IrElementTransformerVoidWithContext() {
-    // This pass ignores suspend function references and function references used in inline arguments to inline functions.
-    private val ignoredFunctionReferences = mutableSetOf<IrFunctionReference>()
+private val IrStatementOrigin?.isLambda
+    get() = this == IrStatementOrigin.LAMBDA || this == IrStatementOrigin.ANONYMOUS_FUNCTION
 
-    private val IrFunctionReference.isIgnored: Boolean
-        get() = !type.isFunctionOrKFunction() || ignoredFunctionReferences.contains(this)
+internal class InlineReferenceLocator(private val context: JvmBackendContext) : IrElementVisitorVoidWithContext() {
+    val inlineReferences = mutableSetOf<IrFunctionReference>()
 
-    override fun lower(irFile: IrFile) = irFile.transformChildrenVoid(this)
+    // For crossinline lambdas, the call site is null as it's probably in a separate class somewhere.
+    // All other lambdas are guaranteed to be inlined into the scope they are declared in.
+    val lambdaToCallSite = mutableMapOf<IrFunction, IrDeclaration?>()
 
-    // Mark function references appearing as inlined arguments to inline functions.
-    override fun visitFunctionAccess(expression: IrFunctionAccessExpression): IrExpression {
+    override fun visitElement(element: IrElement) = element.acceptChildrenVoid(this)
+
+    override fun visitFunctionAccess(expression: IrFunctionAccessExpression) {
         val function = expression.symbol.owner
         if (function.isInlineFunctionCall(context)) {
             for (parameter in function.valueParameters) {
@@ -66,16 +69,41 @@ internal class CallableReferenceLowering(private val context: JvmBackendContext)
                 if (!isInlineIrExpression(valueArgument))
                     continue
 
-                if (valueArgument is IrFunctionReference) {
-                    ignoredFunctionReferences.add(valueArgument)
-                } else if (valueArgument is IrBlock) {
-                    ignoredFunctionReferences.addIfNotNull(valueArgument.statements.filterIsInstance<IrFunctionReference>().singleOrNull())
+                val reference = when (valueArgument) {
+                    is IrFunctionReference -> valueArgument
+                    is IrBlock -> valueArgument.statements.filterIsInstance<IrFunctionReference>().singleOrNull()
+                    else -> null
+                } ?: continue
+
+                inlineReferences.add(reference)
+                if (valueArgument is IrBlock && valueArgument.origin.isLambda) {
+                    lambdaToCallSite[reference.symbol.owner] =
+                        if (parameter.isCrossinline) null else currentScope!!.irElement as IrDeclaration
                 }
             }
         }
         return super.visitFunctionAccess(expression)
     }
 
+    companion object {
+        fun scan(context: JvmBackendContext, element: IrElement) =
+            InlineReferenceLocator(context).apply { element.accept(this, null) }
+    }
+}
+
+// Originally copied from K/Native
+internal class CallableReferenceLowering(private val context: JvmBackendContext) : FileLoweringPass, IrElementTransformerVoidWithContext() {
+    // This pass ignores suspend function references and function references used in inline arguments to inline functions.
+    private val ignoredFunctionReferences = mutableSetOf<IrFunctionReference>()
+
+    private val IrFunctionReference.isIgnored: Boolean
+        get() = !type.isFunctionOrKFunction() || ignoredFunctionReferences.contains(this)
+
+    override fun lower(irFile: IrFile) {
+        ignoredFunctionReferences.addAll(InlineReferenceLocator.scan(context, irFile).inlineReferences)
+        irFile.transformChildrenVoid(this)
+    }
+
     override fun visitBlock(expression: IrBlock): IrExpression {
         if (!expression.origin.isLambda)
             return super.visitBlock(expression)
@@ -403,9 +431,6 @@ internal class CallableReferenceLowering(private val context: JvmBackendContext)
         }
     }
 
-    private val IrStatementOrigin?.isLambda
-        get() = this == IrStatementOrigin.LAMBDA || this == IrStatementOrigin.ANONYMOUS_FUNCTION
-
     private val currentDeclarationParent
         get() = allScopes.last { it.irElement is IrDeclarationParent }.irElement as IrDeclarationParent
 }

compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/lower/SyntheticAccessorLowering.kt

@@ -45,8 +45,10 @@ internal val syntheticAccessorPhase = makeIrFilePhase(
 
 private class SyntheticAccessorLowering(val context: JvmBackendContext) : IrElementTransformerVoidWithContext(), FileLoweringPass {
     private val pendingTransformations = mutableListOf<Function0<Unit>>()
+    private val inlineLambdaToCallSite = mutableMapOf<IrFunction, IrDeclaration?>()
 
     override fun lower(irFile: IrFile) {
+        inlineLambdaToCallSite.putAll(InlineReferenceLocator.scan(context, irFile).lambdaToCallSite)
         irFile.transformChildrenVoid(this)
         pendingTransformations.forEach { it() }
     }
@@ -437,6 +439,16 @@ private class SyntheticAccessorLowering(val context: JvmBackendContext) : IrElem
                 this == JavaVisibilities.PROTECTED_AND_PACKAGE ||
                 this == JavaVisibilities.PROTECTED_STATIC_VISIBILITY
 
+    private fun IrDeclaration.getAccessContext(withSuper: Boolean): IrDeclarationContainer? = when {
+        this is IrDeclarationContainer -> this
+        // Accesses from public inline functions can actually be anywhere. For protected inline functions
+        // calling methods on `super` we need an accessor to satisfy INVOKESPECIAL constraints.
+        this is IrFunction && isInline && !visibility.isPrivate && (withSuper || !visibility.isProtected) -> null
+        // For inline lambdas, we can navigate to the only call site directly.
+        this in inlineLambdaToCallSite -> inlineLambdaToCallSite[this]?.getAccessContext(withSuper)
+        else -> (parent as? IrDeclaration)?.getAccessContext(withSuper)
+    }
+
     private fun IrSymbol.isAccessible(withSuper: Boolean, thisObjReference: IrClassSymbol?): Boolean {
         /// We assume that IR code that reaches us has been checked for correctness at the frontend.
         /// This function needs to single out those cases where Java accessibility rules differ from Kotlin's.
@@ -454,15 +466,9 @@ private class SyntheticAccessorLowering(val context: JvmBackendContext) : IrElem
 
         // If local variables are accessible by Kotlin rules, they also are by Java rules.
         val symbolDeclarationContainer = (declaration.parent as? IrDeclarationContainer) as? IrElement ?: return true
+        val contextDeclarationContainer = (currentScope!!.irElement as IrDeclaration).getAccessContext(withSuper) ?: return false
 
-        // Within inline functions, we have to assume the worst.
-        val function = currentFunction?.irElement as IrFunction?
-        if (function?.isInline == true && !function.visibility.isPrivate && (withSuper || !function.visibility.isProtected))
-            return false
-
-        val contextDeclarationContainer = allScopes.lastOrNull { it.irElement is IrDeclarationContainer }?.irElement
-
-        val samePackage = declaration.getPackageFragment()?.fqName == contextDeclarationContainer?.getPackageFragment()?.fqName
+        val samePackage = declaration.getPackageFragment()?.fqName == contextDeclarationContainer.getPackageFragment()?.fqName
         return when {
             declaration.visibility.isPrivate && symbolDeclarationContainer != contextDeclarationContainer -> false
             declaration.visibility.isProtected && !samePackage &&