InlineProperties.java
/*
* Copyright 2012 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 static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.base.Preconditions.checkState;
import com.google.javascript.jscomp.NodeTraversal.AbstractPostOrderCallback;
import com.google.javascript.rhino.FunctionTypeI;
import com.google.javascript.rhino.IR;
import com.google.javascript.rhino.JSDocInfo;
import com.google.javascript.rhino.Node;
import com.google.javascript.rhino.TypeI;
import com.google.javascript.rhino.jstype.JSTypeNative;
import java.util.HashMap;
import java.util.Map;
/**
* InlineProperties attempts to find references to properties that are known to be constants and
* inline the known value.
*
* <p>This pass relies on type information to find these property references and properties are
* assumed to be constant if they are assigned exactly once, unconditionally, in either of the
* following contexts: (1) statically on a constructor, or (2) on a class's prototype.
*
* <p>The current implementation only inlines immutable values (as defined by
* NodeUtil.isImmutableValue).
*
* @author johnlenz@google.com (John Lenz)
*/
final class InlineProperties implements CompilerPass {
private final AbstractCompiler compiler;
private static class PropertyInfo {
PropertyInfo(TypeI type, Node value) {
this.type = type;
this.value = value;
}
final TypeI type;
final Node value;
}
private static final PropertyInfo INVALIDATED = new PropertyInfo(null, null);
private final Map<String, PropertyInfo> props = new HashMap<>();
private final InvalidatingTypes invalidatingTypes;
InlineProperties(AbstractCompiler compiler) {
this.compiler = compiler;
this.invalidatingTypes = new InvalidatingTypes.Builder(compiler.getTypeIRegistry())
// TODO(sdh): consider allowing inlining properties of global this
// (we already reserve extern'd names, so this should be safe).
.disallowGlobalThis()
.addTypesInvalidForPropertyRenaming()
// NOTE: Mismatches are less important to this pass than to (dis)ambiguate properties.
// This pass doesn't remove values (it only inlines them when the type is known), so
// it isn't necessary to invalidate due to implicit interface uses.
.addAllTypeMismatches(compiler.getTypeMismatches())
.build();
invalidateExternProperties();
}
private void invalidateExternProperties() {
// Invalidate properties defined in externs.
for (String name : compiler.getExternProperties()) {
props.put(name, INVALIDATED);
}
}
/** This method gets the JSType from the Node argument and verifies that it is present. */
private TypeI getTypeI(Node n) {
TypeI type = n.getTypeI();
if (type == null) {
return compiler.getTypeIRegistry().getNativeType(JSTypeNative.UNKNOWN_TYPE);
} else {
return type;
}
}
@Override
public void process(Node externs, Node root) {
// Find and replace the properties in non-extern AST.
NodeTraversal.traverseEs6(compiler, root, new GatherCandidates());
NodeTraversal.traverseEs6(compiler, root, new ReplaceCandidates());
}
class GatherCandidates extends AbstractPostOrderCallback {
@Override
public void visit(NodeTraversal t, Node n, Node parent) {
boolean invalidatingPropRef = false;
String propName = null;
if (n.isGetProp()) {
propName = n.getLastChild().getString();
if (parent.isAssign()) {
invalidatingPropRef = !isValidCandidateDefinition(t, n, parent);
} else if (NodeUtil.isLValue(n)) {
// Other LValue references invalidate
invalidatingPropRef = true;
} else if (parent.isDelProp()) {
// Deletes invalidate
invalidatingPropRef = true;
} else {
// A property read doesn't invalidate
invalidatingPropRef = false;
}
} else if (n.isStringKey()) {
propName = n.getString();
// For now, any object literal key invalidates
// TODO(johnlenz): support prototype properties like:
// foo.prototype = { a: 1, b: 2 };
// TODO(johnlenz): Object.create(), Object.createProperty
invalidatingPropRef = true;
}
if (invalidatingPropRef) {
checkNotNull(propName);
invalidateProperty(propName);
}
}
/** @return Whether this is a valid definition for a candidate property. */
private boolean isValidCandidateDefinition(NodeTraversal t, Node n, Node parent) {
checkState(n.isGetProp() && parent.isAssign(), n);
Node src = n.getFirstChild();
String propName = n.getLastChild().getString();
Node value = parent.getLastChild();
if (src.isThis()) {
// This is a simple assignment like:
// this.foo = 1;
if (inConstructor(t)) {
// This maybe a valid assignment.
return maybeStoreCandidateValue(getTypeI(src), propName, value);
}
} else if (t.inGlobalHoistScope()
&& src.isGetProp()
&& src.getLastChild().getString().equals("prototype")) {
// This is a prototype assignment like:
// x.prototype.foo = 1;
TypeI instanceType = maybeGetInstanceTypeFromPrototypeRef(src);
if (instanceType != null) {
return maybeStoreCandidateValue(instanceType, propName, value);
}
} else if (t.inGlobalHoistScope()) {
// This is a static assignment like:
// x.foo = 1;
TypeI targetType = getTypeI(src);
if (targetType != null && targetType.isConstructor()) {
return maybeStoreCandidateValue(targetType, propName, value);
}
}
return false;
}
private TypeI maybeGetInstanceTypeFromPrototypeRef(Node src) {
TypeI ownerType = getTypeI(src.getFirstChild());
if (ownerType.isConstructor()) {
FunctionTypeI functionType = ownerType.toMaybeFunctionType();
return functionType.getInstanceType();
}
return null;
}
private void invalidateProperty(String propName) {
props.put(propName, INVALIDATED);
}
/**
* Adds the candidate property to the map if it meets all constness and immutability criteria,
* and is not already present in the map. If the property was already present, it is
* invalidated. Returns true if the property was successfully added.
*/
private boolean maybeStoreCandidateValue(TypeI type, String propName, Node value) {
checkNotNull(value);
if (type.toMaybeObjectType() != null) {
type = type.toMaybeObjectType().withoutStrayProperties();
}
if (!props.containsKey(propName)
&& !invalidatingTypes.isInvalidating(type)
&& NodeUtil.isImmutableValue(value)
&& NodeUtil.isExecutedExactlyOnce(value)) {
props.put(propName, new PropertyInfo(type, value));
return true;
}
return false;
}
private boolean inConstructor(NodeTraversal t) {
Node root = t.getEnclosingFunction();
if (root == null) {
return false;
}
JSDocInfo info = NodeUtil.getBestJSDocInfo(root);
return info != null && info.isConstructor();
}
}
class ReplaceCandidates extends AbstractPostOrderCallback {
@Override
public void visit(NodeTraversal t, Node n, Node parent) {
if (n.isGetProp() && !NodeUtil.isLValue(n)) {
Node target = n.getFirstChild();
String propName = n.getLastChild().getString();
PropertyInfo info = props.get(propName);
if (info != null
&& info != INVALIDATED
&& isMatchingType(target, info.type)) {
Node replacement = info.value.cloneTree();
if (NodeUtil.mayHaveSideEffects(n.getFirstChild(), compiler)) {
replacement = IR.comma(n.removeFirstChild(), replacement).srcref(n);
}
parent.replaceChild(n, replacement);
compiler.reportChangeToEnclosingScope(replacement);
}
}
}
private boolean isMatchingType(Node n, TypeI src) {
src = src.restrictByNotNullOrUndefined();
TypeI dest = getTypeI(n).restrictByNotNullOrUndefined();
if (!invalidatingTypes.isInvalidating(dest)) {
if (dest.isConstructor() || src.isConstructor()) {
// Don't inline constructor properties referenced from
// subclass constructor references. This would be appropriate
// for ES6 class with Class-side inheritence but not
// traditional Closure classes from which subclass constructor
// don't inherit the super-classes constructor properties.
return dest.equals(src);
} else {
return dest.isSubtypeOf(src);
}
}
return false;
}
}
}