[JVM IR] Mangle variable names for anonymous parameters in lambdas.

compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/JvmLower.kt

@@ -237,6 +237,7 @@ private val tailrecPhase = makeIrFilePhase<JvmBackendContext>(
 
 @Suppress("Reformat")
 private val jvmFilePhases =
+        renameAnonymousParametersLowering then
         typeAliasAnnotationMethodsPhase then
         stripTypeAliasDeclarationsPhase then
         provisionalFunctionExpressionPhase then

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

@@ -0,0 +1,85 @@
+/*
+ * 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.backend.jvm.lower
+
+import org.jetbrains.kotlin.backend.common.FileLoweringPass
+import org.jetbrains.kotlin.backend.common.IrElementTransformerVoidWithContext
+import org.jetbrains.kotlin.backend.common.phaser.makeIrFilePhase
+import org.jetbrains.kotlin.backend.jvm.JvmBackendContext
+import org.jetbrains.kotlin.codegen.getNameForDestructuredParameterOrNull
+import org.jetbrains.kotlin.descriptors.ReceiverParameterDescriptor
+import org.jetbrains.kotlin.descriptors.ValueParameterDescriptor
+import org.jetbrains.kotlin.ir.declarations.IrFile
+import org.jetbrains.kotlin.ir.declarations.IrValueParameter
+import org.jetbrains.kotlin.ir.declarations.impl.IrValueParameterImpl
+import org.jetbrains.kotlin.ir.descriptors.WrappedReceiverParameterDescriptor
+import org.jetbrains.kotlin.ir.descriptors.WrappedValueParameterDescriptor
+import org.jetbrains.kotlin.ir.expressions.IrExpression
+import org.jetbrains.kotlin.ir.expressions.IrGetValue
+import org.jetbrains.kotlin.ir.expressions.impl.IrGetValueImpl
+import org.jetbrains.kotlin.ir.symbols.impl.IrValueParameterSymbolImpl
+import org.jetbrains.kotlin.name.Name
+import org.jetbrains.kotlin.psi.KtParameter
+import org.jetbrains.kotlin.resolve.DescriptorToSourceUtils
+import org.jetbrains.kotlin.resolve.calls.util.isSingleUnderscore
+import org.jetbrains.kotlin.utils.addToStdlib.safeAs
+
+internal val renameAnonymousParametersLowering = makeIrFilePhase(
+    ::RenameAnonymousParametersLowering,
+    name = "RenameAnonymousParameters",
+    description = "Mangles variable names for anonymous parameters (only allowed in lambdas)"
+)
+
+private class RenameAnonymousParametersLowering(val context: JvmBackendContext) : FileLoweringPass, IrElementTransformerVoidWithContext() {
+
+    val oldParameterToNew: MutableMap<IrValueParameter, IrValueParameter> = mutableMapOf()
+
+    override fun lower(irFile: IrFile) = irFile.transformChildrenVoid()
+
+    override fun visitValueParameter(declaration: IrValueParameter) =
+        declaration.computeNewParameterName()?.let { name ->
+            val descriptor = if (declaration.descriptor is ReceiverParameterDescriptor) {
+                WrappedReceiverParameterDescriptor(declaration.descriptor.annotations)
+            } else {
+                WrappedValueParameterDescriptor(declaration.descriptor.annotations)
+            }
+            IrValueParameterImpl(
+                declaration.startOffset, declaration.endOffset,
+                declaration.origin,
+                IrValueParameterSymbolImpl(descriptor),
+                name,
+                declaration.index,
+                declaration.type,
+                declaration.varargElementType,
+                declaration.isCrossinline,
+                declaration.isNoinline
+            ).apply {
+                descriptor.bind(this)
+                parent = declaration.parent
+                defaultValue = declaration.defaultValue
+                annotations += declaration.annotations
+                oldParameterToNew[declaration] = this
+            }
+        } ?: super.visitValueParameter(declaration)
+
+    override fun visitGetValue(expression: IrGetValue): IrExpression {
+        val oldParameter = expression.symbol.owner
+        return oldParameterToNew[oldParameter]?.let {
+            IrGetValueImpl(expression.startOffset, expression.endOffset, it.type, it.symbol)
+        } ?: super.visitGetValue(expression)
+    }
+
+    private fun IrValueParameter.computeNewParameterName(): Name? {
+        // Consistent with naming on old (non-IR) backend; see FunctionCodegen.java.
+        descriptor.safeAs<ValueParameterDescriptor>()?.let {
+            getNameForDestructuredParameterOrNull(it)?.let { return Name.identifier(it) }
+            if (DescriptorToSourceUtils.getSourceFromDescriptor(it)?.safeAs<KtParameter>()?.isSingleUnderscore == true) {
+                return Name.identifier("\$noName_${it.index}")
+            }
+        }
+        return null
+    }
+}

compiler/testData/checkLocalVariablesTable/destructuringInLambdas.kt

@@ -1,4 +1,3 @@
-// IGNORE_BACKEND: JVM_IR
 data class A(val x: String, val y: Int)
 
 fun foo(a: A, block: (A) -> String): String = block(a)

compiler/testData/checkLocalVariablesTable/destructuringInlineLambda.kt

@@ -1,4 +1,3 @@
-// IGNORE_BACKEND: JVM_IR
 inline fun foo(x: (Int, Station) -> Unit) {
     x(1, Station(null, "", 1))
 }

compiler/testData/checkLocalVariablesTable/underscoreNames.kt

@@ -1,4 +1,3 @@
-// IGNORE_BACKEND: JVM_IR
 data class A(val x: Double = 1.0, val y: String = "", val z: Char = '0')
 
 fun foo(a: A, block: (A, String, Int) -> String): String = block(a, "", 1)