Implement inlining of default parameters in JS BE

Fix KT-17910

js/js.inliner/src/org/jetbrains/kotlin/js/inline/clean/removeDefaultInitializers.kt

@@ -18,18 +18,16 @@ package org.jetbrains.kotlin.js.inline.clean
 
 import org.jetbrains.kotlin.js.backend.ast.*
 import org.jetbrains.kotlin.js.backend.ast.metadata.hasDefaultValue
-
-import org.jetbrains.kotlin.js.inline.util.toIdentitySet
+import org.jetbrains.kotlin.js.backend.ast.metadata.staticRef
 import org.jetbrains.kotlin.js.inline.util.zipWithDefault
 import org.jetbrains.kotlin.js.translate.context.Namer
 import org.jetbrains.kotlin.js.translate.utils.JsAstUtils
+import org.jetbrains.kotlin.js.translate.utils.JsAstUtils.decomposeAssignmentToVariable
 import org.jetbrains.kotlin.js.translate.utils.JsAstUtils.flattenStatement
 
 /**
  * Removes initializers for default parameters with defined arguments given
  * Expands initializers for default parameters with undefined arguments given
- *
- * @see isInitializer
  */
 fun removeDefaultInitializers(arguments: List<JsExpression>, parameters: List<JsParameter>, body: JsBlock) {
     val toRemove = getDefaultParamsNames(arguments, parameters, initialized = true)
@@ -45,8 +43,11 @@ fun removeDefaultInitializers(arguments: List<JsExpression>, parameters: List<Js
         when {
             name != null && name in toRemove ->
                 listOf<JsStatement>()
-            name != null && name in toExpand ->
-                flattenStatement((it as JsIf).thenStatement)
+            name != null && name in toExpand -> {
+                val thenStatement = (it as JsIf).thenStatement
+                markAssignmentAsStaticRef(name, thenStatement)
+                flattenStatement(thenStatement)
+            }
             else ->
                 listOf(it)
         }
@@ -56,6 +57,19 @@ fun removeDefaultInitializers(arguments: List<JsExpression>, parameters: List<Js
     statements.addAll(newStatements)
 }
 
+private fun markAssignmentAsStaticRef(name: JsName, node: JsNode) {
+    node.accept(object : RecursiveJsVisitor() {
+        override fun visitBinaryExpression(x: JsBinaryOperation) {
+            decomposeAssignmentToVariable(x)?.let { (assignmentTarget, assignmentExpr) ->
+                if (assignmentTarget == name) {
+                    assignmentTarget.staticRef = assignmentExpr
+                }
+            }
+            super.visitBinaryExpression(x)
+        }
+    })
+}
+
 private fun getNameFromInitializer(statement: JsStatement): JsName? {
     val ifStmt = (statement as? JsIf)
     val testExpr = ifStmt?.ifExpression
@@ -118,6 +132,6 @@ private fun getDefaultParamsNames(
                                    .filter { initialized == !JsAstUtils.isUndefinedExpression(it.first) }
 
     val names = relevantParams.map { it.second.name }
-    return names.toIdentitySet()
+    return names.toSet()
 }
 

js/js.inliner/src/org/jetbrains/kotlin/js/inline/util/namingUtils.kt

@@ -44,6 +44,7 @@ fun aliasArgumentsIfNeeded(
     for (defaultParam in defaultParams) {
         val paramName = defaultParam.name
         val freshName = JsScope.declareTemporaryName(paramName.ident)
+        freshName.copyMetadataFrom(paramName)
         context.newVar(freshName)
 
         context.replaceName(paramName, freshName.makeRef())