[JS IR BE] Create temporary variables with wrapped descriptors.

compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/lower/LateinitLowering.kt

@@ -81,7 +81,7 @@ class NullableFieldsDeclarationLowering(val backendContext: CommonBackendContext
         getter.body = IrBlockBodyImpl(startOffset, endOffset) {
             val irBuilder = backendContext.createIrBuilder(getter.symbol, startOffset, endOffset)
             irBuilder.run {
-                val resultVar = scope.createTemporaryVariable(
+                val resultVar = scope.createTmpVariable(
                     irGetField(getter.dispatchReceiverParameter?.let { irGet(it) }, backingField)
                 )
                 resultVar.parent = getter

compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/lower/ReturnableBlockLowering.kt

@@ -86,7 +86,7 @@ class ReturnableBlockTransformer(val context: CommonBackendContext, val containe
         val scopeSymbol = currentScope?.scope?.scopeOwnerSymbol ?: containerSymbol
         val builder = context.createIrBuilder(scopeSymbol!!)
         val variable by lazy {
-            builder.scope.createTemporaryVariableDeclaration(expression.type, "tmp\$ret\$${labelCnt++}", true)
+            builder.scope.createTmpVariable(expression.type, "tmp\$ret\$${labelCnt++}", true)
         }
 
         val loop by lazy {

compiler/ir/backend.common/src/org/jetbrains/kotlin/ir/builders/IrBuilders.kt

@@ -17,6 +17,7 @@
 package org.jetbrains.kotlin.ir.builders
 
 import org.jetbrains.kotlin.ir.IrElement
+import org.jetbrains.kotlin.ir.UNDEFINED_OFFSET
 import org.jetbrains.kotlin.ir.declarations.IrDeclarationOrigin
 import org.jetbrains.kotlin.ir.declarations.IrVariable
 import org.jetbrains.kotlin.ir.declarations.impl.IrVariableImpl
@@ -56,6 +57,34 @@ fun <T : IrElement> IrStatementsBuilder<T>.createTmpVariable(
     return variable
 }
 
+fun Scope.createTmpVariable(
+    irType: IrType,
+    nameHint: String? = null,
+    isMutable: Boolean = false,
+    initializer: IrExpression? = null,
+    origin: IrDeclarationOrigin = IrDeclarationOrigin.IR_TEMPORARY_VARIABLE,
+    startOffset: Int = UNDEFINED_OFFSET,
+    endOffset: Int = UNDEFINED_OFFSET
+): IrVariable {
+    val descriptor = WrappedVariableDescriptor()
+    val symbol = IrVariableSymbolImpl(descriptor)
+    return IrVariableImpl(
+        startOffset,
+        endOffset,
+        origin,
+        symbol,
+        Name.identifier(nameHint ?: "tmp"),
+        irType,
+        isMutable,
+        isConst = false,
+        isLateinit = false
+    ).apply {
+        this.initializer = initializer
+        parent = getLocalDeclarationParent()
+        descriptor.bind(this)
+    }
+}
+
 fun Scope.createTmpVariable(
     irExpression: IrExpression,
     nameHint: String? = null,