Replace deprecated join with joinToString

compiler/frontend/src/org/jetbrains/kotlin/psi/DebugTextUtil.kt

@@ -283,12 +283,12 @@ private object DebugTextBuildingVisitor : KtVisitor<String, Unit>() {
 
     fun renderChildren(element: KtElementImplStub<*>, separator: String, prefix: String = "", postfix: String = ""): String? {
         val childrenTexts = element.getStub()?.getChildrenStubs()?.map { (it?.getPsi() as? KtElement)?.getDebugText() }
-        return childrenTexts?.filterNotNull()?.join(separator, prefix, postfix) ?: element.getText()
+        return childrenTexts?.filterNotNull()?.joinToString(separator, prefix, postfix) ?: element.getText()
     }
 
     fun render(element: KtElementImplStub<*>, vararg relevantChildren: KtElement?): String? {
         if (element.getStub() == null) return element.getText()
-        return relevantChildren.filterNotNull().map { it.getDebugText() }.join("", "", "")
+        return relevantChildren.filterNotNull().map { it.getDebugText() }.joinToString("", "", "")
     }
 }
 

compiler/frontend/src/org/jetbrains/kotlin/psi/KtCodeFragment.kt

@@ -97,7 +97,7 @@ public abstract class KtCodeFragment(
     }
 
     override fun importsToString(): String {
-        return myImports.join(IMPORT_SEPARATOR)
+        return myImports.joinToString(IMPORT_SEPARATOR)
     }
 
     override fun addImportsFromString(imports: String?) {
@@ -110,7 +110,7 @@ public abstract class KtCodeFragment(
     }
 
     public fun importsAsImportList(): KtImportList? {
-        return KtPsiFactory(this).createFile(myImports.join("\n")).getImportList()
+        return KtPsiFactory(this).createFile(myImports.joinToString("\n")).getImportList()
     }
 
     override fun setVisibilityChecker(checker: JavaCodeFragment.VisibilityChecker?) { }

compiler/frontend/src/org/jetbrains/kotlin/psi/stubs/impl/KotlinStubBaseImpl.kt

@@ -36,7 +36,7 @@ public open class KotlinStubBaseImpl<T : KtElementImplStub<*>>(parent: StubEleme
         if (propertiesValues.isEmpty()) {
             return ""
         }
-        return propertiesValues.join(separator = ", ", prefix = "[", postfix = "]")
+        return propertiesValues.joinToString(separator = ", ", prefix = "[", postfix = "]")
     }
 
     private fun renderPropertyValues(stubInterface: Class<out Any?>): List<String> {