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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.rhino.IR;
import com.google.javascript.rhino.Node;
import com.google.javascript.rhino.jstype.JSType;
/** An optimization pass to re-write J2CL Equality.$same. */
public class J2clEqualitySameRewriterPass extends AbstractPeepholeOptimization {
private final boolean useTypes;
private boolean shouldRunJ2clPasses;
J2clEqualitySameRewriterPass(boolean useTypes) {
this.useTypes = useTypes;
}
@Override
void beginTraversal(AbstractCompiler compiler) {
super.beginTraversal(compiler);
shouldRunJ2clPasses = J2clSourceFileChecker.shouldRunJ2clPasses(compiler);
}
@Override
Node optimizeSubtree(Node node) {
if (!shouldRunJ2clPasses) {
return node;
}
if (!isEqualitySameCall(node)) {
return node;
}
Node replacement = trySubstituteEqualitySame(node);
if (replacement != node) {
replacement = replacement.useSourceInfoIfMissingFrom(node);
node.replaceWith(replacement);
compiler.reportChangeToEnclosingScope(replacement);
}
return replacement;
}
private Node trySubstituteEqualitySame(Node callNode) {
Node firstExpr = callNode.getSecondChild();
Node secondExpr = callNode.getLastChild();
if (!NodeUtil.isLiteralValue(firstExpr, true) && !NodeUtil.isLiteralValue(secondExpr, true)) {
return callNode;
}
if (NodeUtil.isNullOrUndefined(firstExpr)) {
// Note that technically 'undefined' might have side effect (see tests) but since at least one
// side is literal, we can still safely re-order.
return rewriteNullCheck(secondExpr, firstExpr);
}
if (NodeUtil.isNullOrUndefined(secondExpr)) {
return rewriteNullCheck(firstExpr, secondExpr);
}
// There is a coercion danger (e.g. 0 == null) but since at least one side is not null, we can
// safely use === that will not trigger any coercion.
return rewriteAsStrictEq(firstExpr, secondExpr);
}
private Node rewriteNullCheck(Node expr, Node nullExpression) {
expr.detach();
nullExpression.detach();
if (useTypes && canOnlyBeObject(expr)) {
return IR.not(expr);
}
// At least one side is null or undefined so no coercion danger with ==.
return IR.eq(expr, nullExpression);
}
private boolean canOnlyBeObject(Node n) {
JSType type = n.getJSType();
if (type == null) {
return false;
}
type = type.restrictByNotNullOrUndefined();
return !type.isUnknownType() && !type.isEmptyType() && !type.isAllType() && type.isObjectType();
}
private Node rewriteAsStrictEq(Node firstExpr, Node secondExpr) {
firstExpr.detach();
secondExpr.detach();
return IR.sheq(firstExpr, secondExpr);
}
private static boolean isEqualitySameCall(Node node) {
return node.isCall()
// Do not optimize if one or both parameters were removed
&& node.hasXChildren(3)
&& 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");
}
}