Some cleanup in JS optimizer

js/js.inliner/src/org/jetbrains/kotlin/js/inline/FunctionInlineMutator.kt

@@ -23,7 +23,6 @@ import org.jetbrains.kotlin.js.inline.context.InliningContext
 import org.jetbrains.kotlin.js.inline.context.NamingContext
 import org.jetbrains.kotlin.js.inline.util.*
 import org.jetbrains.kotlin.js.inline.util.rewriters.ReturnReplacingVisitor
-import org.jetbrains.kotlin.js.translate.utils.JsAstUtils.newVar
 
 class FunctionInlineMutator
 private constructor(

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

@@ -157,8 +157,7 @@ internal class TemporaryAssignmentElimination(private val root: JsBlock) {
 
                 val assignment = JsAstUtils.decomposeAssignmentToVariable(x.expression)
                 if (assignment != null) {
-                    val (name, value) = assignment
-                    val usage = getUsage(name)
+                    val usage = getUsage(assignment.first)
                     if (usage is Usage.Declaration) {
                         usage.count++
                     }

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

@@ -190,7 +190,7 @@ internal class TemporaryVariableElimination(private val root: JsStatement) {
                 val name = x.name
                 if (x.qualifier == null && name != null && shouldConsiderTemporary(name)) {
                     hasChanges = true
-                    val newExpr = definedValues[name]!!
+                    val newExpr = definedValues[name] ?: JsLiteral.UNDEFINED
                     ctx.replaceMe(accept(newExpr))
                     usages[name] = usages[name]!! - 1
                     return false
@@ -201,6 +201,17 @@ internal class TemporaryVariableElimination(private val root: JsStatement) {
             override fun visit(x: JsBreak, ctx: JsContext<*>) = false
 
             override fun visit(x: JsContinue, ctx: JsContext<*>) = false
+
+            override fun visit(x: JsReturn, ctx: JsContext<*>): Boolean {
+                val returnValue = x.expression
+                if (returnValue is JsNameRef) {
+                    val name = returnValue.name
+                    if (returnValue.qualifier == null && name != null && name in temporary && definitions[name] ?: 0 == 0) {
+                        x.expression = null
+                    }
+                }
+                return super.visit(x, ctx)
+            }
         }.accept(root)
     }