[JS IR] Explicitly convert Long values to String in string concatenation

#KT-39891 Fixed

compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/JsLoweringPhases.kt

@@ -161,6 +161,12 @@ private val expectDeclarationsRemovingPhase = makeDeclarationTransformerPhase(
     description = "Remove expect declaration from module fragment"
 )
 
+private val stringConcatenationLoweringPhase = makeJsModulePhase(
+    ::JsStringConcatenationLowering,
+    name = "JsStringConcatenationLowering",
+    description = "Call toString() for values of some types when concatenating strings"
+).toModuleLowering()
+
 private val lateinitNullableFieldsPhase = makeDeclarationTransformerPhase(
     ::NullableFieldsForLateinitCreationLowering,
     name = "LateinitNullableFields",
@@ -820,6 +826,7 @@ private val loweringList = listOf<Lowering>(
     copyInlineFunctionBodyLoweringPhase,
     removeInlineDeclarationsWithReifiedTypeParametersLoweringPhase,
     createScriptFunctionsPhase,
+    stringConcatenationLoweringPhase,
     callableReferenceLowering,
     singleAbstractMethodPhase,
     tailrecLoweringPhase,

compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/JsStringConcatenationLowering.kt

@@ -0,0 +1,89 @@
+/*
+ * 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.backend.js.lower
+
+import org.jetbrains.kotlin.backend.common.CommonBackendContext
+import org.jetbrains.kotlin.backend.common.FileLoweringPass
+import org.jetbrains.kotlin.ir.backend.js.ir.JsIrBuilder
+import org.jetbrains.kotlin.ir.declarations.IrFile
+import org.jetbrains.kotlin.ir.expressions.*
+import org.jetbrains.kotlin.ir.symbols.IrFunctionSymbol
+import org.jetbrains.kotlin.ir.types.*
+import org.jetbrains.kotlin.ir.visitors.IrElementTransformerVoid
+import org.jetbrains.kotlin.ir.visitors.transformChildrenVoid
+import org.jetbrains.kotlin.utils.addToStdlib.safeAs
+
+class JsStringConcatenationLowering(val context: CommonBackendContext) : FileLoweringPass {
+    override fun lower(irFile: IrFile) {
+        irFile.transformChildrenVoid(JsStringConcatenationTransformer(context))
+    }
+}
+
+private class JsStringConcatenationTransformer(val context: CommonBackendContext) : IrElementTransformerVoid() {
+
+    private val IrType.shouldExplicitlyConvertToString: Boolean
+        get() {
+            // If the type is Long or a supertype of Long, we want to call toString() on values of that type.
+            // See KT-39891
+            if (this !is IrSimpleType) return false
+            return when (classifier.signature) {
+                IdSignatureValues.any, IdSignatureValues.comparable, IdSignatureValues.number, IdSignatureValues._long -> true
+                else -> false
+            }
+        }
+
+    private fun IrExpression.explicitlyConvertedToString(): IrExpression {
+        assert(type.shouldExplicitlyConvertToString)
+
+        return if (type.isNullable()) {
+            JsIrBuilder.buildCall(context.ir.symbols.extensionToString).apply {
+                extensionReceiver = this@explicitlyConvertedToString
+            }
+        } else {
+            JsIrBuilder.buildCall(context.ir.symbols.memberToString).apply {
+                dispatchReceiver = this@explicitlyConvertedToString
+            }
+        }
+    }
+
+    private val IrFunctionSymbol.isStringPlus: Boolean
+        get() = context.ir.symbols.isStringPlus(this)
+
+    override fun visitCall(expression: IrCall): IrExpression {
+        fun explicitlyConvertToStringIfNeeded(): IrExpression {
+            val lastArgIndex = expression.valueArgumentsCount - 1
+            val plusArg = expression.getValueArgument(lastArgIndex) ?: return super.visitCall(expression)
+            if (!plusArg.type.shouldExplicitlyConvertToString)
+                return super.visitCall(expression)
+
+            expression.putValueArgument(lastArgIndex, plusArg.explicitlyConvertedToString())
+            return expression
+        }
+
+        if (expression.valueArgumentsCount == 0)
+            return super.visitCall(expression)
+
+        if (expression.symbol.isStringPlus)
+            return explicitlyConvertToStringIfNeeded()
+
+        if (expression.dispatchReceiver.safeAs<IrFunctionReference>()?.symbol?.isStringPlus == true)
+            return explicitlyConvertToStringIfNeeded()
+
+        return super.visitCall(expression)
+    }
+
+    override fun visitStringConcatenation(expression: IrStringConcatenation): IrExpression {
+        expression
+            .transformChildrenVoid(object : IrElementTransformerVoid() {
+                override fun visitExpression(expression: IrExpression): IrExpression {
+                    if (expression.type.shouldExplicitlyConvertToString)
+                        return expression.explicitlyConvertedToString()
+                    return expression
+                }
+            })
+        return super.visitStringConcatenation(expression)
+    }
+}

compiler/testData/codegen/box/intrinsics/kt8666.kt

@@ -1,20 +1,26 @@
-// IGNORE_BACKEND: JS_IR
-// IGNORE_BACKEND: JS_IR_ES6
 val MAX_LONG = "9223372036854775807"
 val PREFIX = "max = "
 
 fun box(): String {
     if (MAX_LONG != "${Long.MAX_VALUE}") return "fail template"
     if (MAX_LONG != "" + Long.MAX_VALUE) return "fail \"\" +"
+    if (MAX_LONG != ("" as String?) + Long.MAX_VALUE) return "fail \"\"? +"
     if (MAX_LONG != "".plus(Long.MAX_VALUE)) return "fail \"\".plus"
+    if (MAX_LONG != ("" as String?).plus(Long.MAX_VALUE)) return "fail \"\"?.plus"
     if (MAX_LONG != (String::plus)("", Long.MAX_VALUE)) return "fail String::plus"
+    if (MAX_LONG != (String?::plus)("", Long.MAX_VALUE)) return "fail String?::plus"
     if (MAX_LONG != (""::plus)(Long.MAX_VALUE)) return "fail \"\"::plus"
+    if (MAX_LONG != (("" as String?)::plus)(Long.MAX_VALUE)) return "fail \"\"?::plus"
 
     if (PREFIX + MAX_LONG != "max = ${Long.MAX_VALUE}") return "fail template with prefix"
     if (PREFIX + MAX_LONG != PREFIX + Long.MAX_VALUE) return "fail \"$PREFIX\" +"
+    if (PREFIX + MAX_LONG != (PREFIX as String?) + Long.MAX_VALUE) return "fail \"$PREFIX\"? +"
     if (PREFIX + MAX_LONG != PREFIX.plus(Long.MAX_VALUE)) return "fail \"$PREFIX\".plus"
+    if (PREFIX + MAX_LONG != (PREFIX as String?).plus(Long.MAX_VALUE)) return "fail \"$PREFIX\"?.plus"
     if (PREFIX + MAX_LONG != (String::plus)(PREFIX, Long.MAX_VALUE)) return "fail String::plus($PREFIX, ...)"
+    if (PREFIX + MAX_LONG != (String?::plus)(PREFIX, Long.MAX_VALUE)) return "fail String?::plus($PREFIX, ...)"
     if (PREFIX + MAX_LONG != (PREFIX::plus)(Long.MAX_VALUE)) return "fail \"$PREFIX\"::plus"
+    if (PREFIX + MAX_LONG != ((PREFIX as String?)::plus)(Long.MAX_VALUE)) return "fail \"$PREFIX\"?::plus"
 
     return "OK"
 }

js/js.translator/testData/box/number/kt26706.kt

@@ -1,5 +1,3 @@
-// IGNORE_BACKEND: JS_IR
-// IGNORE_BACKEND: JS_IR_ES6
 // KJS_WITH_FULL_RUNTIME
 // EXPECTED_REACHABLE_NODES: 1378
 package foo
@@ -11,9 +9,13 @@ fun box(): String {
     if (" ${x.toLong() as Number}" != " $x") return "FAIL 3"
     if (" ${x.toLong() as Any}" != " $x") return "FAIL 4"
     if (" ${x.toLong() as Long?}" != " $x") return "FAIL 5"
-    if (" ${x.toLong() as Comparable<Long>?}" != " $x") return "FAIL 6"
+    if (" ${null as Long?}" != " null") return "FAIL 6"
-    if (" ${x.toLong() as Number?}" != " $x") return "FAIL 7"
+    if (" ${x.toLong() as Comparable<Long>?}" != " $x") return "FAIL 7"
-    if (" ${x.toLong() as Any?}" != " $x") return "FAIL 8"
+    if (" ${null as Comparable<Long>?}" != " null") return "FAIL 8"
+    if (" ${x.toLong() as Number?}" != " $x") return "FAIL 9"
+    if (" ${null as Number?}" != " null") return "FAIL 10"
+    if (" ${x.toLong() as Any?}" != " $x") return "FAIL 11"
+    if (" ${null as Any?}" != " null") return "FAIL 12"
 
     return "OK"
 }