[Wasm] Add a basic end-to-end sourcemap generation in wasm backend

More constructions/instructions will be supported separately.

compiler/cli/cli-js/src/org/jetbrains/kotlin/cli/js/K2JsIrCompiler.kt

@@ -367,18 +367,23 @@ class K2JsIrCompiler : CLICompiler<K2JSCompilerArguments>() {
                 if (arguments.irDce) {
                     eliminateDeadDeclarations(allModules, backendContext)
                 }
+
+                val sourceMapFileName = if (configuration.getBoolean(JSConfigurationKeys.SOURCE_MAP)) "$outputName.map" else null
+
                 val res = compileWasm(
                     allModules = allModules,
                     backendContext = backendContext,
                     emitNameSection = arguments.wasmDebug,
                     allowIncompleteImplementations = arguments.irDce,
                     generateWat = true,
+                    sourceMapFileName = sourceMapFileName
                 )
 
                 writeCompilationResult(
                     result = res,
                     dir = outputDir,
-                    fileNameBase = outputName
+                    fileNameBase = outputName,
+                    sourceMapFileName = sourceMapFileName
                 )
 
                 return OK

compiler/ir/backend.wasm/src/org/jetbrains/kotlin/backend/wasm/compiler.kt

@@ -11,20 +11,31 @@ import org.jetbrains.kotlin.backend.common.serialization.linkerissues.checkNoUnb
 import org.jetbrains.kotlin.backend.wasm.ir2wasm.WasmCompiledModuleFragment
 import org.jetbrains.kotlin.backend.wasm.ir2wasm.WasmModuleFragmentGenerator
 import org.jetbrains.kotlin.backend.wasm.lower.markExportedDeclarations
+import org.jetbrains.kotlin.config.CompilerConfiguration
 import org.jetbrains.kotlin.ir.backend.js.MainModule
 import org.jetbrains.kotlin.ir.backend.js.ModulesStructure
+import org.jetbrains.kotlin.ir.backend.js.SourceMapsInfo
 import org.jetbrains.kotlin.ir.backend.js.loadIr
 import org.jetbrains.kotlin.ir.declarations.IrFactory
 import org.jetbrains.kotlin.ir.declarations.IrModuleFragment
 import org.jetbrains.kotlin.ir.util.ExternalDependenciesGenerator
 import org.jetbrains.kotlin.ir.util.patchDeclarationParents
+import org.jetbrains.kotlin.js.sourceMap.SourceFilePathResolver
+import org.jetbrains.kotlin.js.sourceMap.SourceMap3Builder
 import org.jetbrains.kotlin.name.FqName
+import org.jetbrains.kotlin.wasm.ir.source.location.SourceLocation
 import org.jetbrains.kotlin.wasm.ir.convertors.WasmIrToBinary
 import org.jetbrains.kotlin.wasm.ir.convertors.WasmIrToText
+import org.jetbrains.kotlin.wasm.ir.source.location.SourceLocationMapping
 import java.io.ByteArrayOutputStream
 import java.io.File
 
-class WasmCompilerResult(val wat: String?, val js: String, val wasm: ByteArray)
+class WasmCompilerResult(
+    val wat: String?,
+    val js: String,
+    val wasm: ByteArray,
+    val sourceMap: String?
+)
 
 fun compileToLoweredIr(
     depsDescriptors: ModulesStructure,
@@ -77,6 +88,7 @@ fun compileWasm(
     emitNameSection: Boolean = false,
     allowIncompleteImplementations: Boolean = false,
     generateWat: Boolean = false,
+    sourceMapFileName: String? = null,
 ): WasmCompilerResult {
     val compiledWasmModule = WasmCompiledModuleFragment(backendContext.irBuiltIns)
     val codeGenerator = WasmModuleFragmentGenerator(backendContext, compiledWasmModule, allowIncompleteImplementations = allowIncompleteImplementations)
@@ -95,16 +107,65 @@ fun compileWasm(
     val js = compiledWasmModule.generateJs()
 
     val os = ByteArrayOutputStream()
-    WasmIrToBinary(os, linkedModule, allModules.last().descriptor.name.asString(), emitNameSection).appendWasmModule()
+
+    val sourceLocationMappings =
+        if (sourceMapFileName != null) mutableListOf<SourceLocationMapping>() else null
+
+    val wasmIrToBinary =
+        WasmIrToBinary(
+            os,
+            linkedModule,
+            allModules.last().descriptor.name.asString(),
+            emitNameSection,
+            sourceMapFileName,
+            sourceLocationMappings
+        )
+
+    wasmIrToBinary.appendWasmModule()
+
     val byteArray = os.toByteArray()
 
     return WasmCompilerResult(
         wat = wat,
         js = js,
-        wasm = byteArray
+        wasm = byteArray,
+        sourceMap = generateSourceMap(backendContext.configuration, sourceLocationMappings)
     )
 }
 
+private fun generateSourceMap(
+    configuration: CompilerConfiguration,
+    sourceLocationMappings: MutableList<SourceLocationMapping>?
+): String? {
+    if (sourceLocationMappings == null) return null
+
+    val sourceMapsInfo = SourceMapsInfo.from(configuration) ?: return null
+
+    val sourceMapBuilder =
+        SourceMap3Builder(null, { error("This should not be called for Kotlin/Wasm") }, sourceMapsInfo.sourceMapPrefix)
+
+    val pathResolver =
+        SourceFilePathResolver.create(sourceMapsInfo.sourceRoots, sourceMapsInfo.sourceMapPrefix, sourceMapsInfo.outputDir)
+
+    var prev: SourceLocation? = null
+
+    for (mapping in sourceLocationMappings) {
+        val location = mapping.sourceLocation as? SourceLocation.Location ?: continue
+
+        if (location == prev) continue
+
+        prev = location
+
+        location.apply {
+            // TODO resulting path goes too deep since temporary directory we compiled first is deeper than final destination.   
+            val relativePath = pathResolver.getPathRelativeToSourceRoots(File(file)).substring(3)
+            sourceMapBuilder.addMapping(relativePath, null, { null }, line, column, null, mapping.offset)
+        }
+    }
+
+    return sourceMapBuilder.build()
+}
+
 fun WasmCompiledModuleFragment.generateJs(): String {
     //language=js
     val runtime = """
@@ -170,7 +231,8 @@ fun generateJsWasmLoader(wasmFilePath: String, externalJs: String): String =
 fun writeCompilationResult(
     result: WasmCompilerResult,
     dir: File,
-    fileNameBase: String = "index",
+    fileNameBase: String,
+    sourceMapFileName: String?
 ) {
     dir.mkdirs()
     if (result.wat != null) {
@@ -180,4 +242,8 @@ fun writeCompilationResult(
 
     val jsWithLoader = generateJsWasmLoader("./$fileNameBase.wasm", result.js)
     File(dir, "$fileNameBase.mjs").writeText(jsWithLoader)
+
+    if (sourceMapFileName != null) {
+        File(dir, sourceMapFileName).writeText(result.sourceMap!!)
+    }
 }

compiler/ir/backend.wasm/src/org/jetbrains/kotlin/backend/wasm/ir2wasm/BodyGenerator.kt

@@ -27,6 +27,8 @@ import org.jetbrains.kotlin.ir.visitors.IrElementVisitorVoid
 import org.jetbrains.kotlin.ir.visitors.acceptVoid
 import org.jetbrains.kotlin.js.config.JSConfigurationKeys
 import org.jetbrains.kotlin.wasm.ir.*
+import org.jetbrains.kotlin.wasm.ir.source.location.SourceLocation
+import org.jetbrains.kotlin.wasm.ir.source.location.withLocation
 
 class BodyGenerator(
     val context: WasmFunctionCodegenContext,
@@ -420,7 +422,9 @@ class BodyGenerator(
 
         } else {
             // Static function call
-            body.buildCall(context.referenceFunction(function.symbol))
+            withLocation(call.getSourceLocation()) {
+                body.buildCall(context.referenceFunction(function.symbol), location)
+            }
         }
 
         // Unit types don't cross function boundaries
@@ -646,7 +650,7 @@ class BodyGenerator(
             body.buildGetLocal(context.referenceLocal(0))
         }
 
-        body.buildInstr(WasmOp.RETURN)
+        body.buildInstr(WasmOp.RETURN, expression.getSourceLocation())
     }
 
     internal fun generateWithExpectedType(expression: IrExpression, expectedType: IrType) {
@@ -883,4 +887,16 @@ class BodyGenerator(
 
         return false
     }
+
+    private fun IrExpression.getSourceLocation(): SourceLocation {
+        val fileEntry = context.irFunction.fileEntry
+        val path = fileEntry.name
+        val startLine = fileEntry.getLineNumber(startOffset)
+        val startColumn = fileEntry.getColumnNumber(startOffset)
+
+        if (startLine < 0 || startColumn < 0) return SourceLocation.NoLocation
+
+        return SourceLocation.Location(path, startLine, startColumn)
+    }
+
 }

js/js.tests/test/org/jetbrains/kotlin/js/testOld/BasicWasmBoxTest.kt

@@ -214,7 +214,7 @@ abstract class BasicWasmBoxTest(
                     )
                 }
 
-                writeCompilationResult(res, dir)
+                writeCompilationResult(res, dir, "index", sourceMapFileName = null)
                 File(dir, "test.mjs").writeText(testJs)
                 ExternalTool(System.getProperty("javascript.engine.path.V8"))
                     .run(

wasm/wasm.ir/build.gradle.kts

@@ -7,6 +7,7 @@ plugins {
 
 dependencies {
     implementation(kotlinStdlib())
+    implementation(kotlinxCollectionsImmutable())
     testImplementation(commonDependency("junit:junit"))
     testCompileOnly(project(":kotlin-test:kotlin-test-jvm"))
     testCompileOnly(project(":kotlin-test:kotlin-test-junit"))

wasm/wasm.ir/src/org/jetbrains/kotlin/wasm/ir/Declarations.kt

@@ -5,6 +5,8 @@
 
 package org.jetbrains.kotlin.wasm.ir
 
+import org.jetbrains.kotlin.wasm.ir.source.location.SourceLocation
+
 
 class WasmModule(
     val functionTypes: List<WasmFunctionType> = emptyList(),
@@ -169,10 +171,30 @@ class WasmStructFieldDeclaration(
     val isMutable: Boolean
 )
 
-class WasmInstr(
+sealed class WasmInstr(
     val operator: WasmOp,
     val immediates: List<WasmImmediate> = emptyList()
-)
+) {
+    abstract val location: SourceLocation?
+}
+
+class WasmInstrWithLocation(
+    operator: WasmOp,
+    immediates: List<WasmImmediate>,
+    override val location: SourceLocation
+) : WasmInstr(operator, immediates) {
+    constructor(
+        operator: WasmOp,
+        location: SourceLocation
+    ) : this(operator, emptyList(), location)
+}
+
+class WasmInstrWithoutLocation(
+    operator: WasmOp,
+    immediates: List<WasmImmediate> = emptyList(),
+) : WasmInstr(operator, immediates) {
+    override val location: SourceLocation? get() = null
+}
 
 data class WasmLimits(
     val minSize: UInt,
@@ -182,4 +204,4 @@ data class WasmLimits(
 data class WasmImportPair(
     val moduleName: String,
     val declarationName: String
-)
+)

wasm/wasm.ir/src/org/jetbrains/kotlin/wasm/ir/WasmExpressionBuilder.kt

@@ -5,12 +5,19 @@
 
 package org.jetbrains.kotlin.wasm.ir
 
+import org.jetbrains.kotlin.wasm.ir.source.location.SourceLocation
+
 abstract class WasmExpressionBuilder {
-    abstract fun buildInstr(op: WasmOp, vararg immediates: WasmImmediate)
+    abstract fun buildInstr(op: WasmOp, location: SourceLocation, vararg immediates: WasmImmediate)
+
+    fun buildInstr(op: WasmOp, vararg immediates: WasmImmediate) {
+        buildInstr(op, SourceLocation.TBDLocation, *immediates)
+    }
+
     abstract var numberOfNestedBlocks: Int
 
-    fun buildConstI32(value: Int) {
-        buildInstr(WasmOp.I32_CONST, WasmImmediate.ConstI32(value))
+    fun buildConstI32(value: Int, location: SourceLocation = SourceLocation.TBDLocation) {
+        buildInstr(WasmOp.I32_CONST, location, WasmImmediate.ConstI32(value))
     }
 
     fun buildConstI64(value: Long) {
@@ -105,8 +112,8 @@ abstract class WasmExpressionBuilder {
         buildBrInstr(WasmOp.BR_IF, absoluteBlockLevel)
     }
 
-    fun buildCall(symbol: WasmSymbol<WasmFunction>) {
-        buildInstr(WasmOp.CALL, WasmImmediate.FuncIdx(symbol))
+    fun buildCall(symbol: WasmSymbol<WasmFunction>, location: SourceLocation = SourceLocation.TBDLocation) {
+        buildInstr(WasmOp.CALL, location, WasmImmediate.FuncIdx(symbol))
     }
 
     fun buildCallIndirect(

wasm/wasm.ir/src/org/jetbrains/kotlin/wasm/ir/WasmIrExpressionBuilder.kt

@@ -5,6 +5,8 @@
 
 package org.jetbrains.kotlin.wasm.ir
 
+import org.jetbrains.kotlin.wasm.ir.source.location.SourceLocation
+
 private fun WasmOp.isOutCfgNode() = when (this) {
     WasmOp.UNREACHABLE, WasmOp.RETURN, WasmOp.THROW, WasmOp.RETHROW, WasmOp.BR, WasmOp.BR_TABLE -> true
     else -> false
@@ -28,8 +30,8 @@ class WasmIrExpressionBuilder(
         get() = expression.lastOrNull()
     private var eatEverythingUntilLevel: Int? = null
 
-    private fun addInstruction(op: WasmOp, immediates: Array<out WasmImmediate>) {
-        val newInstruction = WasmInstr(op, immediates.toList())
+    private fun addInstruction(op: WasmOp, location: SourceLocation, immediates: Array<out WasmImmediate>) {
+        val newInstruction = WasmInstrWithLocation(op, immediates.toList(), location)
         expression.add(newInstruction)
     }
 
@@ -46,21 +48,21 @@ class WasmIrExpressionBuilder(
         return eatLevel
     }
 
-    override fun buildInstr(op: WasmOp, vararg immediates: WasmImmediate) {
+    override fun buildInstr(op: WasmOp, location: SourceLocation, vararg immediates: WasmImmediate) {
         val currentEatUntil = getCurrentEatLevel(op)
         if (currentEatUntil != null) {
             if (currentEatUntil <= numberOfNestedBlocks) return
         } else {
             if (op.isOutCfgNode()) {
                 eatEverythingUntilLevel = numberOfNestedBlocks
-                addInstruction(op, immediates)
+                addInstruction(op, location, immediates)
                 return
             }
         }
 
         val lastInstruction = lastInstr
         if (lastInstruction == null) {
-            addInstruction(op, immediates)
+            addInstruction(op, location, immediates)
             return
         }
         val lastOperator = lastInstruction.operator
@@ -78,13 +80,13 @@ class WasmIrExpressionBuilder(
                 val localGetNumber = (immediates.firstOrNull() as? WasmImmediate.LocalIdx)?.value
                 if (localGetNumber == localSetNumber) {
                     expression.removeLast()
-                    addInstruction(WasmOp.LOCAL_TEE, immediates)
+                    addInstruction(WasmOp.LOCAL_TEE, location, immediates)
                     return
                 }
             }
         }
 
-        addInstruction(op, immediates)
+        addInstruction(op, location, immediates)
     }
 
     override var numberOfNestedBlocks: Int = 0
@@ -98,4 +100,4 @@ inline fun buildWasmExpression(body: WasmExpressionBuilder.() -> Unit): MutableL
     val res = mutableListOf<WasmInstr>()
     WasmIrExpressionBuilder(res).body()
     return res
-}
+}

wasm/wasm.ir/src/org/jetbrains/kotlin/wasm/ir/convertors/WasmBinaryToIR.kt

@@ -442,8 +442,8 @@ class WasmBinaryToIR(val b: MyByteReader) {
             }
         }
 
-
-        return WasmInstr(op, immediates)
+        // We don't need location in Binary -> WasmIR, yet.
+        return WasmInstrWithoutLocation(op, immediates)
     }
 
     private fun readTypeDeclaration(): WasmTypeDeclaration {

wasm/wasm.ir/src/org/jetbrains/kotlin/wasm/ir/convertors/WasmIrToBinary.kt

@@ -3,16 +3,30 @@
  * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
  */
 
-@file:OptIn(ExperimentalUnsignedTypes::class)
-
 package org.jetbrains.kotlin.wasm.ir.convertors
 
 import org.jetbrains.kotlin.wasm.ir.*
 import java.io.ByteArrayOutputStream
 import java.io.OutputStream
+import kotlinx.collections.immutable.*
+import org.jetbrains.kotlin.wasm.ir.source.location.Box
+import org.jetbrains.kotlin.wasm.ir.source.location.SourceLocation
+import org.jetbrains.kotlin.wasm.ir.source.location.SourceLocationMapping
 
-class WasmIrToBinary(outputStream: OutputStream, val module: WasmModule, val moduleName: String, val emitNameSection: Boolean) {
-    var b: ByteWriter = ByteWriter.OutputStream(outputStream)
+class WasmIrToBinary(
+    outputStream: OutputStream,
+    val module: WasmModule,
+    val moduleName: String,
+    val emitNameSection: Boolean,
+    private val sourceMapFileName: String? = null,
+    private val sourceLocationMappings: MutableList<SourceLocationMapping>? = null
+) {
+    private var b: ByteWriter = ByteWriter.OutputStream(outputStream)
+
+    // "Stack" of offsets waiting initialization. 
+    // Since blocks has as a prefix variable length number encoding its size we can't calculate absolute offsets inside those blocks 
+    // until we generate whole block and generate size. So, we put them into "stack" and initialize as soo as we have all required data.
+    private var offsets = persistentListOf<Box>()
 
     fun appendWasmModule() {
         b.writeUInt32(0x6d736100u) // WebAssembly magic
@@ -114,10 +128,18 @@ class WasmIrToBinary(outputStream: OutputStream, val module: WasmModule, val mod
                 data.forEach { appendData(it) }
             }
 
-            //text section (should be placed after data)
+            // text section (should be placed after data)
             if (emitNameSection) {
                 appendTextSection(definedFunctions)
             }
+
+            if (sourceMapFileName != null) {
+                // Custom section with URL to sourcemap
+                appendSection(0u) {
+                    b.writeString("sourceMappingURL")
+                    b.writeString(sourceMapFileName)
+                }
+            }
         }
     }
 
@@ -183,6 +205,10 @@ class WasmIrToBinary(outputStream: OutputStream, val module: WasmModule, val mod
     }
 
     private fun appendInstr(instr: WasmInstr) {
+        instr.location?.let {
+            sourceLocationMappings?.add(SourceLocationMapping(offsets + Box(b.written), it))
+        }
+
         val opcode = instr.operator.opcode
         if (opcode > 0xFF) {
             b.writeByte((opcode ushr 8).toByte())
@@ -241,14 +267,21 @@ class WasmIrToBinary(outputStream: OutputStream, val module: WasmModule, val mod
         withVarUInt32PayloadSizePrepended { content() }
     }
 
-    @OptIn(ExperimentalStdlibApi::class)
-    fun withVarUInt32PayloadSizePrepended(fn: () -> Unit) {
+    private fun withVarUInt32PayloadSizePrepended(fn: () -> Unit) {
+        val box = Box(-1)
+        val previousOffsets = offsets
+        offsets += box
+
         val previousWriter = b
         val newWriter = b.createTemp()
         b = newWriter
         fn()
         b = previousWriter
         b.writeVarUInt32(newWriter.written)
+
+        box.value = b.written
+        offsets = previousOffsets
+
         b.write(newWriter)
     }
 
@@ -350,7 +383,7 @@ class WasmIrToBinary(outputStream: OutputStream, val module: WasmModule, val mod
         }
         appendType(c.type)
         b.writeVarUInt1(c.isMutable)
-        appendExpr(c.init)
+        appendExpr(c.init, SourceLocation.TBDLocation)
     }
 
     private fun appendTag(t: WasmTag) {
@@ -365,9 +398,9 @@ class WasmIrToBinary(outputStream: OutputStream, val module: WasmModule, val mod
         b.writeVarUInt32(t.type.id!!)
     }
 
-    private fun appendExpr(expr: Iterable<WasmInstr>) {
+    private fun appendExpr(expr: Iterable<WasmInstr>, location: SourceLocation) {
         expr.forEach { appendInstr(it) }
-        appendInstr(WasmInstr(WasmOp.END))
+        appendInstr(WasmInstrWithLocation(WasmOp.END, location))
     }
 
     private fun appendExport(export: WasmExport<*>) {
@@ -393,7 +426,7 @@ class WasmIrToBinary(outputStream: OutputStream, val module: WasmModule, val mod
                 funcIndices.forEach { b.writeVarUInt32(it) }
             } else {
                 element.values.forEach {
-                    appendExpr((it as WasmTable.Value.Expression).expr)
+                    appendExpr((it as WasmTable.Value.Expression).expr, SourceLocation.TBDLocation)
                 }
             }
         }
@@ -417,18 +450,18 @@ class WasmIrToBinary(outputStream: OutputStream, val module: WasmModule, val mod
                 when {
                     tableId == 0 && isFuncIndices -> {
                         b.writeByte(0x0)
-                        appendExpr(mode.offset)
+                        appendExpr(mode.offset, SourceLocation.TBDLocation)
                     }
                     isFuncIndices -> {
                         b.writeByte(0x2)
                         appendModuleFieldReference(mode.table)
-                        appendExpr(mode.offset)
+                        appendExpr(mode.offset, SourceLocation.TBDLocation)
                         writeTypeOrKind()
                     }
                     else -> {
                         b.writeByte(0x6)
                         appendModuleFieldReference(mode.table)
-                        appendExpr(mode.offset)
+                        appendExpr(mode.offset, SourceLocation.TBDLocation)
                         writeTypeOrKind()
                     }
                 }
@@ -452,7 +485,7 @@ class WasmIrToBinary(outputStream: OutputStream, val module: WasmModule, val mod
                 }
             }
 
-            appendExpr(function.instructions)
+            appendExpr(function.instructions, SourceLocation.TBDLocation)
         }
     }
 
@@ -465,7 +498,7 @@ class WasmIrToBinary(outputStream: OutputStream, val module: WasmModule, val mod
                     b.writeByte(2)
                     b.writeVarUInt32(mode.memoryIdx)
                 }
-                appendExpr(mode.offset)
+                appendExpr(mode.offset, SourceLocation.TBDLocation)
             }
             WasmDataMode.Passive -> b.writeByte(1)
         }

wasm/wasm.ir/src/org/jetbrains/kotlin/wasm/ir/source/location/Box.kt

@@ -0,0 +1,8 @@
+/*
+ * Copyright 2010-2022 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.wasm.ir.source.location
+
+class Box(var value: Int)

wasm/wasm.ir/src/org/jetbrains/kotlin/wasm/ir/source/location/LocationHolder.kt

@@ -0,0 +1,15 @@
+/*
+ * Copyright 2010-2022 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.wasm.ir.source.location
+
+@JvmInline
+value class LocationHolder(val location: SourceLocation)
+
+inline fun <R> withLocation(location: SourceLocation, body: LocationHolder.() -> R): R = LocationHolder(location).body()
+
+inline fun <R> withNoLocation(body: LocationHolder.() -> R): R = withLocation(SourceLocation.NoLocation, body)
+
+inline fun <R> withTBDLocation(body: LocationHolder.() -> R): R = withLocation<R>(SourceLocation.TBDLocation, body)

wasm/wasm.ir/src/org/jetbrains/kotlin/wasm/ir/source/location/SourceLocation.kt

@@ -0,0 +1,13 @@
+/*
+ * Copyright 2010-2022 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.wasm.ir.source.location
+
+sealed class SourceLocation {
+    object NoLocation: SourceLocation()
+    object TBDLocation: SourceLocation()
+
+    data class Location(val file: String, val line: Int, val column: Int) : SourceLocation()
+}

wasm/wasm.ir/src/org/jetbrains/kotlin/wasm/ir/source/location/SourceLocationMapping.kt

@@ -0,0 +1,20 @@
+/*
+ * Copyright 2010-2022 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.wasm.ir.source.location
+
+class SourceLocationMapping(
+    // Offsets in generating binary, initialized lazily. Since blocks has as a prefix variable length number encoding its size 
+    // we can't calculate absolute offsets inside those blocks until we generate whole block and generate size.
+    private val offsets: List<Box>,
+    val sourceLocation: SourceLocation
+) {
+    val offset by lazy {
+        offsets.sumOf {
+            assert(it.value >= 0) { "Offset must be >=0 but ${it.value}" }
+            it.value
+        }
+    }
+}