org.jetbrains.kotlin.js.inline.clean.RedundantVariableDeclarationElimination.kt Maven / Gradle / Ivy
/*
* Copyright 2010-2016 JetBrains s.r.o.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.jetbrains.kotlin.js.inline.clean
import org.jetbrains.kotlin.js.backend.ast.*
import org.jetbrains.kotlin.js.backend.ast.metadata.synthetic
import org.jetbrains.kotlin.js.inline.util.collectFreeVariables
internal class RedundantVariableDeclarationElimination(private val root: JsStatement) {
private val usages = mutableSetOf()
private var hasChanges = false
fun apply(): Boolean {
analyze()
perform()
return hasChanges
}
private fun analyze() {
object : JsVisitorWithContextImpl() {
override fun visit(x: JsNameRef, ctx: JsContext<*>): Boolean {
val name = x.name
if (name != null && x.qualifier == null) {
usages += name
}
return super.visit(x, ctx)
}
override fun visit(x: JsBreak, ctx: JsContext<*>) = false
override fun visit(x: JsContinue, ctx: JsContext<*>) = false
override fun visit(x: JsFunction, ctx: JsContext<*>): Boolean {
usages += x.collectFreeVariables()
return false
}
}.accept(root)
}
private fun perform() {
object : JsVisitorWithContextImpl() {
override fun endVisit(x: JsVars, ctx: JsContext<*>) {
if (x.synthetic) {
if (x.vars.removeAll { it.initExpression == null && it.name !in usages }) {
hasChanges = true
}
if (x.vars.isEmpty()) {
ctx.removeMe()
}
}
super.endVisit(x, ctx)
}
override fun visit(x: JsFunction, ctx: JsContext<*>) = false
}.accept(root)
}
}