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J2clEqualitySameRewriterPass.java
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J2clEqualitySameRewriterPass.java
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/*
* Copyright 2016 The Closure Compiler Authors.
*
* 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 com.google.javascript.jscomp;
import com.google.javascript.jscomp.NodeTraversal.AbstractPostOrderCallback;
import com.google.javascript.rhino.IR;
import com.google.javascript.rhino.Node;
/** An optimization pass to re-write J2CL Equality.$same. */
public class J2clEqualitySameRewriterPass extends AbstractPostOrderCallback
implements CompilerPass {
/** Whether to use "==" or "===". */
private static enum Eq {
DOUBLE,
TRIPLE
}
private final AbstractCompiler compiler;
J2clEqualitySameRewriterPass(AbstractCompiler compiler) {
this.compiler = compiler;
}
@Override
public void process(Node externs, Node root) {
if (!J2clSourceFileChecker.shouldRunJ2clPasses(compiler)) {
return;
}
NodeTraversal.traverseEs6(compiler, root, this);
}
@Override
public void visit(NodeTraversal t, Node node, Node parent) {
if (isEqualitySameCall(node)) {
trySubstituteEqualitySame(node);
}
}
private void trySubstituteEqualitySame(Node callNode) {
Node firstExpr = callNode.getSecondChild();
Node secondExpr = callNode.getLastChild();
if (NodeUtil.isNullOrUndefined(firstExpr) || NodeUtil.isNullOrUndefined(secondExpr)) {
// At least one side is null or undefined so no coercion danger.
rewriteToEq(callNode, firstExpr, secondExpr, Eq.DOUBLE);
return;
}
if (NodeUtil.isLiteralValue(firstExpr, true) || NodeUtil.isLiteralValue(secondExpr, true)) {
// There is a coercion danger but since at least one side is not null, we can use === that
// will not trigger any coercion.
rewriteToEq(callNode, firstExpr, secondExpr, Eq.TRIPLE);
return;
}
}
private void rewriteToEq(Node callNode, Node firstExpr, Node secondExpr, Eq eq) {
Node parent = callNode.getParent();
firstExpr.detach();
secondExpr.detach();
Node replacement =
eq == Eq.DOUBLE ? IR.eq(firstExpr, secondExpr) : IR.sheq(firstExpr, secondExpr);
parent.replaceChild(callNode, replacement.useSourceInfoIfMissingFrom(callNode));
compiler.reportChangeToEnclosingScope(parent);
}
private static boolean isEqualitySameCall(Node node) {
return node.isCall() && isEqualitySameMethodName(node.getFirstChild());
}
private static boolean isEqualitySameMethodName(Node fnName) {
if (!fnName.isQualifiedName()) {
return false;
}
// NOTE: This should be rewritten to use method name + file name of definition site
// like other J2CL passes, which is more precise.
String originalQname = fnName.getOriginalQualifiedName();
return originalQname.endsWith(".$same") && originalQname.contains("Equality");
}
}