CrossModuleCodeMotion.java
/*
* Copyright 2008 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.CrossModuleReferenceCollector.TopLevelStatement;
import com.google.javascript.rhino.IR;
import com.google.javascript.rhino.Node;
import com.google.javascript.rhino.Token;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.BitSet;
import java.util.Collection;
import java.util.Deque;
import java.util.HashMap;
import java.util.HashSet;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
/**
* A compiler pass for moving global variable declarations and assignments to their properties to a
* deeper module if possible.
*
* <ol>
* <li> Collect all global-level statements and the references they contain.
* <li> Statements that do not declare global variables are assumed to exist for their side-effects
* and are considered immovable.
* <li> Statements that declare global variables may be movable. See CrossModuleReferenceCollector.
* <li> Within each module gather all declarations for a single global variable into a
* DeclarationStatementGroup (DSG). Keep track of the references to other globals that appear
* in the DSG. A DSG is movable if all of its statements are movable.
* <li> Gather the DSGs for each global variable and note all of the modules that contain immovable
* references to it.
* <li> The global variables form a directed graph. Global A has an edge to B if A has a DSG with a
* reference to B.
* <li> Convert this to a directed-acyclic graph by grouping together all of the strongly-connected
* global variables into GlobalSymbolCycles. There is an edge from GlobalSymbolCycle A to
* GlobalSymbolCycle B if A contains a DSG (in one of its GlobalSymbols) that contains a
* reference to a GlobalSymbol in B.
* <li> Sort the GlobalSymbolCycles into a list c[1], c[2], c[3],..., c[n], such that there are no
* references to GlobalSymbols in c[i] from DSGs in GlobalSymbolCycles c[i+1]...c[n].
* <li> Traverse the list in that order, so statements for GlobalSymbol X will only be moved after
* all statements that refer to X have already been moved.
* <li> Within a GlobalSymbolCycle, combine statements from DSGs in the same module and keep them
* in the same order when moving them.
* </ol>
*/
class CrossModuleCodeMotion implements CompilerPass {
private final AbstractCompiler compiler;
private final JSModuleGraph graph;
/**
* Map from module to the node in that module that should parent variable declarations that have
* to be moved into that module
*/
private final Map<JSModule, Node> moduleInsertionPointMap = new HashMap<>();
private final boolean parentModuleCanSeeSymbolsDeclaredInChildren;
/**
* Creates an instance.
*
* @param compiler The compiler
*/
CrossModuleCodeMotion(
AbstractCompiler compiler,
JSModuleGraph graph,
boolean parentModuleCanSeeSymbolsDeclaredInChildren) {
this.compiler = compiler;
this.graph = graph;
this.parentModuleCanSeeSymbolsDeclaredInChildren = parentModuleCanSeeSymbolsDeclaredInChildren;
}
@Override
public void process(Node externs, Node root) {
// If there are <2 modules, then we will never move anything, so we're done
if (graph != null && graph.getModuleCount() > 1) {
CrossModuleReferenceCollector referenceCollector =
new CrossModuleReferenceCollector(compiler, new Es6SyntacticScopeCreator(compiler));
referenceCollector.process(root);
Collection<GlobalSymbol> globalSymbols =
new GlobalSymbolCollector().collectGlobalSymbols(referenceCollector);
moveGlobalSymbols(globalSymbols);
addInstanceofGuards(globalSymbols);
}
}
private void addInstanceofGuards(Collection<GlobalSymbol> globalSymbols) {
for (GlobalSymbol globalSymbol : globalSymbols) {
for (InstanceofReference instanceofReference : globalSymbol.instanceofReferencesToGuard) {
if (!globalSymbol.declarationsCoverModule(instanceofReference.getModule())) {
addGuardToInstanceofReference(instanceofReference.getReference().getNode());
}
}
}
}
/** Collects all global symbols, their declaration statements and references. */
private class GlobalSymbolCollector {
final Map<Var, GlobalSymbol> globalSymbolforVar = new HashMap<>();
/**
* Returning the symbols in the reverse order in which they are defined helps to minimize
* unnecessary reordering of declaration statements.
*/
final Deque<GlobalSymbol> symbolStack = new ArrayDeque<>();
Collection<GlobalSymbol> collectGlobalSymbols(
CrossModuleReferenceCollector referenceCollector) {
for (TopLevelStatement statement : referenceCollector.getTopLevelStatements()) {
if (statement.isDeclarationStatement()) {
processDeclarationStatement(statement);
} else {
processImmovableStatement(statement);
}
}
return symbolStack;
}
private void processImmovableStatement(TopLevelStatement statement) {
for (Reference ref : statement.getNonDeclarationReferences()) {
processImmovableReference(ref, statement.getModule());
}
}
private void processImmovableReference(Reference ref, JSModule module) {
GlobalSymbol globalSymbol = getGlobalSymbol(ref.getSymbol());
if (parentModuleCanSeeSymbolsDeclaredInChildren) {
// It is possible to move the declaration of `Foo` after
// `'undefined' != typeof Foo && x instanceof Foo`.
// We'll add the undefined check, if necessary.
Node n = ref.getNode();
if (isGuardedInstanceofReference(n) || isUndefinedTypeofGuardReference(n)) {
return;
} else if (isUnguardedInstanceofReference(n)) {
ImmovableInstanceofReference instanceofReference =
new ImmovableInstanceofReference(module, ref);
globalSymbol.instanceofReferencesToGuard.push(instanceofReference);
return;
}
}
globalSymbol.addImmovableReference(module);
}
private void processDeclarationStatement(TopLevelStatement statement) {
GlobalSymbol declaredSymbol =
getGlobalSymbol(statement.getDeclaredNameReference().getSymbol());
DeclarationStatementGroup dsg = declaredSymbol.addDeclarationStatement(statement);
processDeclarationStatementContainedReferences(statement, declaredSymbol, dsg);
}
private void processDeclarationStatementContainedReferences(
TopLevelStatement statement, GlobalSymbol declaredSymbol, DeclarationStatementGroup dsg) {
for (Reference ref : statement.getNonDeclarationReferences()) {
GlobalSymbol refSymbol = getGlobalSymbol(ref.getSymbol());
if (refSymbol.equals(declaredSymbol)) {
continue; // ignore circular reference
}
if (parentModuleCanSeeSymbolsDeclaredInChildren) {
// It is possible to move the declaration of `Foo` after
// `'undefined' != typeof Foo && x instanceof Foo`.
// We'll add the undefined check, if necessary.
Node n = ref.getNode();
if (isGuardedInstanceofReference(n) || isUndefinedTypeofGuardReference(n)) {
continue;
} else if (isUnguardedInstanceofReference(n)) {
MovableInstanceofReference instanceofReference =
new MovableInstanceofReference(dsg, ref);
refSymbol.instanceofReferencesToGuard.push(instanceofReference);
continue;
}
}
dsg.addReferenceToGlobalSymbol(refSymbol);
refSymbol.addReferringGlobalSymbol(declaredSymbol);
}
}
private GlobalSymbol getGlobalSymbol(Var var) {
GlobalSymbol globalSymbol = globalSymbolforVar.get(var);
if (globalSymbol == null) {
globalSymbol = new GlobalSymbol(var);
globalSymbolforVar.put(var, globalSymbol);
symbolStack.push(globalSymbol);
}
return globalSymbol;
}
}
/**
* Moves all of the declaration statements that can move to their best possible module location.
*/
private void moveGlobalSymbols(Collection<GlobalSymbol> globalSymbols) {
for (GlobalSymbolCycle globalSymbolCycle :
new OrderAndCombineGlobalSymbols(globalSymbols).orderAndCombine()) {
// Symbols whose declarations refer to each other must be grouped together and their
// declaration statements moved together.
globalSymbolCycle.moveDeclarationStatements();
}
}
/** Represents a global symbol whose declaration statements may be moved. */
private class GlobalSymbol {
final Var var;
/**
* As we traverse the statements in execution order the top of the stack represents the most
* recently seen DSG for the variable.
*/
final Deque<DeclarationStatementGroup> dsgStack = new ArrayDeque<>();
final BitSet modulesWithImmovableReferences = new BitSet(graph.getModuleCount());
/**
* Symbols whose declaration statements refer to this symbol.
*
* This is a LinkedHashSet in order to enforce a consistent ordering when we iterate over these
* to identify cycles. This guarantees that the order in which statements are moved won't
* depend on the arbitrary ordering of HashSet.
*/
final Set<GlobalSymbol> referencingGlobalSymbols = new LinkedHashSet<>();
/** Instanceof references we may need to update with a guard after moving declarations. */
Deque<InstanceofReference> instanceofReferencesToGuard = new ArrayDeque<>();
/** Used by OrderAndCombineGlobalSymbols to find reference cycles. */
int preorderNumber = -1;
/** Used by OrderAndCombineGlobalSymbols to find reference cycles. */
boolean hasBeenAssignedToAStronglyConnectedComponent = false;
/** Used to confirm all symbols get moved in the correct order. */
boolean isMoveDeclarationStatementsDone = false;
GlobalSymbol(Var var) {
this.var = var;
}
@Override
public String toString() {
return var.getName();
}
void addImmovableReference(JSModule module) {
modulesWithImmovableReferences.set(module.getIndex());
}
/** Adds the statement to the appropriate DeclarationStatementGroup and returns it. */
DeclarationStatementGroup addDeclarationStatement(TopLevelStatement statement) {
JSModule module = statement.getModule();
DeclarationStatementGroup lastDsg = dsgStack.peek();
if (lastDsg == null) {
lastDsg = new DeclarationStatementGroup(this, module);
dsgStack.push(lastDsg);
}
DeclarationStatementGroup statementDsg;
if (module.equals(lastDsg.currentModule)) {
statementDsg = lastDsg;
} else {
// new module requires a new DSG
statementDsg = new DeclarationStatementGroup(this, module);
dsgStack.push(statementDsg);
}
statementDsg.statementStack.push(statement);
return statementDsg;
}
void addReferringGlobalSymbol(GlobalSymbol declaredSymbol) {
referencingGlobalSymbols.add(declaredSymbol);
}
/**
* Does the module depend on at least one of the modules containing declaration statements for
* this symbol?
*/
boolean declarationsCoverModule(JSModule module) {
for (DeclarationStatementGroup dsg : dsgStack) {
if (module.equals(dsg.currentModule) || graph.dependsOn(module, dsg.currentModule)) {
return true;
}
}
return false;
}
}
/**
* Represents a set of global symbols that all refer to each other, and so must be considered
* for movement as a group.
*/
private class GlobalSymbolCycle {
final Deque<GlobalSymbol> symbols = new ArrayDeque<>();
void addSymbol(GlobalSymbol symbol) {
symbols.add(symbol);
}
void moveDeclarationStatements() {
for (GlobalSymbol symbol : symbols) {
checkState(!symbol.isMoveDeclarationStatementsDone, "duplicate attempt to move %s", symbol);
}
BitSet modulesWithImmovableReferences = new BitSet(graph.getModuleCount());
List<DeclarationStatementGroupCycle> cyclesLatestFirst = getDsgCyclesLatestFirst();
for (DeclarationStatementGroupCycle dsgCycle : cyclesLatestFirst) {
// Each move may change modulesWithImmovableReferences
for (GlobalSymbol symbol : symbols) {
modulesWithImmovableReferences.or(symbol.modulesWithImmovableReferences);
}
dsgCycle.moveToPreferredModule(modulesWithImmovableReferences);
}
for (GlobalSymbol symbol : symbols) {
symbol.isMoveDeclarationStatementsDone = true;
}
}
List<DeclarationStatementGroupCycle> getDsgCyclesLatestFirst() {
List<DeclarationStatementGroupCycle> cyclesLatestFirst = new ArrayList<>();
Deque<DeclarationStatementGroup> dsgsLatestFirst = getDsgsLatestFirst();
DeclarationStatementGroupCycle cycle = null;
for (DeclarationStatementGroup dsg : dsgsLatestFirst) {
if (cycle == null || !cycle.currentModule.equals(dsg.currentModule)) {
cycle = new DeclarationStatementGroupCycle(this, dsg.currentModule);
cyclesLatestFirst.add(cycle);
}
cycle.dsgs.add(dsg);
}
return cyclesLatestFirst;
}
private Deque<DeclarationStatementGroup> getDsgsLatestFirst() {
Deque<DeclarationStatementGroup> resultStack = new ArrayDeque<>();
for (GlobalSymbol symbol : symbols) {
Deque<DeclarationStatementGroup> stack1 = resultStack;
Deque<DeclarationStatementGroup> stack2 = new ArrayDeque<>(symbol.dsgStack);
resultStack = new ArrayDeque<>(stack1.size() + stack2.size());
while (true) {
if (stack1.isEmpty()) {
resultStack.addAll(stack2);
break;
} else if (stack2.isEmpty()) {
resultStack.addAll(stack1);
break;
} else {
DeclarationStatementGroup dsg1 = stack1.peek();
DeclarationStatementGroup dsg2 = stack2.peek();
if (dsg1.currentModule.getIndex() > dsg2.currentModule.getIndex()) {
resultStack.add(stack1.pop());
checkState(
stack1.isEmpty()
|| stack1.peek().currentModule.getIndex() <= dsg1.currentModule.getIndex(),
"DSG stacks are out of order.");
} else {
resultStack.add(stack2.pop());
checkState(
stack2.isEmpty()
|| stack2.peek().currentModule.getIndex() <= dsg2.currentModule.getIndex(),
"DSG stacks are out of order.");
}
}
}
}
return resultStack;
}
}
private void addGuardToInstanceofReference(Node referenceNode) {
checkState(
isUnguardedInstanceofReference(referenceNode),
"instanceof Reference is already guarded: %s",
referenceNode);
Node instanceofNode = checkNotNull(referenceNode.getParent());
Node referenceForTypeOf = referenceNode.cloneNode();
Node tmp = IR.block();
// Wrap "foo instanceof Bar" in
// "('undefined' != typeof Bar && foo instanceof Bar)"
instanceofNode.replaceWith(tmp);
Node and =
IR.and(
new Node(Token.NE, IR.string("undefined"), new Node(Token.TYPEOF, referenceForTypeOf)),
instanceofNode);
and.useSourceInfoIfMissingFromForTree(instanceofNode);
tmp.replaceWith(and);
compiler.reportChangeToEnclosingScope(and);
}
/**
* A group of declaration statements that must be moved (or not) as a group.
*
* <p>All of the statements must be in the same module initially. If there are declarations for
* the same variable in different modules, they will be grouped separately.
*/
private static class DeclarationStatementGroup {
final GlobalSymbol declaredGlobalSymbol;
final Set<GlobalSymbol> referencedGlobalSymbols = new HashSet<>();
/** module containing the statements */
JSModule currentModule;
/** statements in the group, latest first */
Deque<TopLevelStatement> statementStack = new ArrayDeque<>();
DeclarationStatementGroup(GlobalSymbol declaredGlobalSymbol, JSModule currentModule) {
this.declaredGlobalSymbol = declaredGlobalSymbol;
this.currentModule = currentModule;
}
boolean allStatementsCanMove() {
for (TopLevelStatement s : statementStack) {
if (!s.isMovableDeclaration()) {
return false;
}
}
return true;
}
void addReferenceToGlobalSymbol(GlobalSymbol refSymbol) {
referencedGlobalSymbols.add(refSymbol);
}
void makeReferencesImmovable() {
declaredGlobalSymbol.addImmovableReference(currentModule);
for (GlobalSymbol symbol : referencedGlobalSymbols) {
checkState(
!symbol.isMoveDeclarationStatementsDone,
"symbol %s moved before referring symbol %s",
symbol,
declaredGlobalSymbol);
symbol.addImmovableReference(currentModule);
}
}
}
/**
* Orders DeclarationStatementGroups so that each DSG appears in the list only after all of the
* DSGs that contain references to it.
*
* <p>DSGs that form cycles are combined into a single DSG. This happens when declarations within
* a module form cycles by referring to each other.
*
* <p>This is an implementation of the path-based strong component algorithm as it is described in
* the Wikipedia article https://en.wikipedia.org/wiki/Path-based_strong_component_algorithm.
*/
private class OrderAndCombineGlobalSymbols {
final Collection<GlobalSymbol> inputSymbols;
/** Tracks DSGs that may be part of a strongly connected component (reference cycle). */
final Deque<GlobalSymbol> componentContents = new ArrayDeque<>();
/** Tracks DSGs that may be the root of a strongly connected component (reference cycle). */
final Deque<GlobalSymbol> componentRoots = new ArrayDeque<>();
/** Filled with lists of strongly connected DSGs as they are discovered. */
final Deque<GlobalSymbolCycle> stronglyConnectedSymbols;
int preorderCounter = 0;
OrderAndCombineGlobalSymbols(Collection<GlobalSymbol> dsgs) {
inputSymbols = dsgs;
stronglyConnectedSymbols = new ArrayDeque<>(dsgs.size());
}
Deque<GlobalSymbolCycle> orderAndCombine() {
for (GlobalSymbol globalSymbol : inputSymbols) {
if (globalSymbol.preorderNumber < 0) {
processGlobalSymbol(globalSymbol);
} // else already processed
}
// At this point stronglyConnectedSymbols has been filled.
return stronglyConnectedSymbols;
}
/**
* Determines to which strongly connected component this GlobalSymbol belongs.
*
* <p>Called exactly once for each GlobalSymbol. When this method returns we will have
* determined which strongly connected component contains globalSymbol. Either:
*
* <ul>
* <li>globalSymbol was the first member of the strongly connected component we encountered,
* and the entire component has now been added to stronglyConnectedSymbols.
* <li>OR, we encountered the first member of the strongly connected component in an earlier
* call to this method on the call stack. In this case the top of componentRoots will be
* the first member, and we'll add the component to stronglyConnectedSymbols once
* execution has fallen back to the call made with that GlobalSymbol.
* </ul>
*/
void processGlobalSymbol(GlobalSymbol symbol) {
// preorderNumber is used to track whether we've already processed a DSG and the order in
// which they have been processed. It is initially -1.
checkState(symbol.preorderNumber < 0, "already processed: %s", symbol);
symbol.preorderNumber = preorderCounter++;
componentRoots.push(symbol); // could be the start of a new strongly connected component
componentContents.push(symbol); // could be part of an existing strongly connected component
for (GlobalSymbol referringSymbol : symbol.referencingGlobalSymbols) {
if (referringSymbol.preorderNumber < 0) {
processGlobalSymbol(referringSymbol);
} else {
if (!referringSymbol.hasBeenAssignedToAStronglyConnectedComponent) {
// This GlobalSymbol is part of a not-yet-completed strongly connected component.
// Back off the potential roots stack to the earliest symbol that is part of the
// component.
while (componentRoots.peek().preorderNumber > referringSymbol.preorderNumber) {
componentRoots.pop();
}
}
}
}
if (componentRoots.peek().equals(symbol)) {
// After exploring all paths from here, this symbol is still at the top of the potential
// component roots stack, so this symbol is the root of a strongly connected component.
componentRoots.pop();
GlobalSymbolCycle cycle = new GlobalSymbolCycle();
// this symbol and all those after it on the componentContents stack are part of a single
// cycle.
GlobalSymbol connectedSymbol;
do {
connectedSymbol = componentContents.pop();
cycle.addSymbol(connectedSymbol);
connectedSymbol.hasBeenAssignedToAStronglyConnectedComponent = true;
} while (!connectedSymbol.equals(symbol));
this.stronglyConnectedSymbols.add(cycle);
}
}
}
/**
* One or more DeclarationStatementGroups that that share the same module and whose declared
* global symbols refer to each other.
*/
private class DeclarationStatementGroupCycle {
GlobalSymbolCycle globalSymbolCycle;
JSModule currentModule;
Deque<DeclarationStatementGroup> dsgs;
DeclarationStatementGroupCycle(GlobalSymbolCycle globalSymbolCycle, JSModule currentModule) {
this.globalSymbolCycle = globalSymbolCycle;
this.currentModule = currentModule;
this.dsgs = new ArrayDeque<>();
}
void moveToPreferredModule(BitSet modulesWithImmovableReferences) {
JSModule preferredModule = getPreferredModule(modulesWithImmovableReferences);
if (!preferredModule.equals(currentModule)) {
moveStatementsToModule(preferredModule);
}
// Now that all the statements have been moved, update the current module for all the DSGs
// and treat all of the references they contain as now immovable.
for (DeclarationStatementGroup dsg : dsgs) {
dsg.currentModule = preferredModule;
dsg.makeReferencesImmovable();
}
}
private void moveStatementsToModule(JSModule preferredModule) {
Node destParent = moduleInsertionPointMap.get(preferredModule);
if (destParent == null) {
destParent = compiler.getNodeForCodeInsertion(preferredModule);
moduleInsertionPointMap.put(preferredModule, destParent);
}
Deque<TopLevelStatement> statementsLastFirst = getStatementsLastFirst();
for (TopLevelStatement statement : statementsLastFirst) {
Node statementNode = statement.getStatementNode();
// Remove it
compiler.reportChangeToEnclosingScope(statementNode);
statementNode.detach();
// Add it to the new spot
destParent.addChildToFront(statementNode);
compiler.reportChangeToEnclosingScope(statementNode);
}
}
private Deque<TopLevelStatement> getStatementsLastFirst() {
Deque<TopLevelStatement> result = new ArrayDeque<>();
for (DeclarationStatementGroup dsg : dsgs) {
// combine previous result with statements for current DSG
Deque<TopLevelStatement> stack1 = new ArrayDeque<>(dsg.statementStack);
Deque<TopLevelStatement> stack2 = result;
result = new ArrayDeque<>(stack1.size() + stack2.size());
while (true) {
if (stack1.isEmpty()) {
result.addAll(stack2);
break;
} else if (stack2.isEmpty()) {
result.addAll(stack1);
break;
} else {
TopLevelStatement s1 = stack1.peek();
TopLevelStatement s2 = stack2.peek();
if (s1.getOriginalOrder() > s2.getOriginalOrder()) {
result.add(stack1.pop());
checkState(
stack1.isEmpty() || stack1.peek().getOriginalOrder() < s1.getOriginalOrder(),
"Statements are recorded in the wrong order.");
} else {
result.add(stack2.pop());
checkState(
stack2.isEmpty() || stack2.peek().getOriginalOrder() < s2.getOriginalOrder(),
"Statements are recorded in the wrong order.");
}
}
}
}
return result;
}
private JSModule getPreferredModule(BitSet modulesWithImmovableReferences) {
if (modulesWithImmovableReferences.isEmpty()) {
return currentModule;
} else if (!allStatementsCanMove()) {
return currentModule;
} else {
return graph.getSmallestCoveringSubtree(currentModule, modulesWithImmovableReferences);
}
}
boolean allStatementsCanMove() {
for (DeclarationStatementGroup dsg : dsgs) {
if (!dsg.allStatementsCanMove()) {
return false;
}
}
return true;
}
}
interface InstanceofReference {
JSModule getModule();
Reference getReference();
}
private static class ImmovableInstanceofReference implements InstanceofReference {
JSModule module;
Reference reference;
ImmovableInstanceofReference(JSModule module, Reference reference) {
this.module = module;
this.reference = reference;
}
@Override
public JSModule getModule() {
return module;
}
@Override
public Reference getReference() {
return reference;
}
}
private static class MovableInstanceofReference implements InstanceofReference {
DeclarationStatementGroup containingDsg;
Reference reference;
MovableInstanceofReference(DeclarationStatementGroup containingDsg, Reference reference) {
this.containingDsg = containingDsg;
this.reference = reference;
}
@Override
public JSModule getModule() {
return containingDsg.currentModule;
}
@Override
public Reference getReference() {
return reference;
}
}
/**
* Is the reference node the first {@code Ref} in an expression like {@code 'undefined' != typeof
* Ref && x instanceof Ref}?
*
* <p>It's safe to ignore this kind of reference when moving the definition of {@code Ref}.
*/
private boolean isUndefinedTypeofGuardReference(Node reference) {
// reference => typeof => `!=`
Node undefinedTypeofGuard = reference.getGrandparent();
if (undefinedTypeofGuard != null
&& isUndefinedTypeofGuardFor(undefinedTypeofGuard, reference)) {
Node andNode = undefinedTypeofGuard.getParent();
return andNode != null
&& andNode.isAnd()
&& isInstanceofFor(andNode.getLastChild(), reference);
} else {
return false;
}
}
/**
* Is the expression of the form {@code 'undefined' != typeof Ref}?
*
* @param expression
* @param reference Ref node must be equivalent to this node
*/
private boolean isUndefinedTypeofGuardFor(Node expression, Node reference) {
if (expression.isNE()) {
Node undefinedString = expression.getFirstChild();
Node typeofNode = expression.getLastChild();
return undefinedString.isString()
&& undefinedString.getString().equals("undefined")
&& typeofNode.isTypeOf()
&& typeofNode.getFirstChild().isEquivalentTo(reference);
} else {
return false;
}
}
/**
* Is the reference node the second {@code Ref} in an expression like {@code 'undefined' != typeof
* Ref && x instanceof Ref}?
*
* <p>It's safe to ignore this kind of reference when moving the definition of {@code Ref}.
*/
private boolean isGuardedInstanceofReference(Node reference) {
Node instanceofNode = reference.getParent();
if (isInstanceofFor(instanceofNode, reference)) {
Node andNode = instanceofNode.getParent();
return andNode != null
&& andNode.isAnd()
&& isUndefinedTypeofGuardFor(andNode.getFirstChild(), reference);
} else {
return false;
}
}
/** Is the reference the right hand side of an {@code instanceof} and not guarded? */
private boolean isUnguardedInstanceofReference(Node reference) {
Node instanceofNode = reference.getParent();
if (isInstanceofFor(instanceofNode, reference)) {
Node andNode = instanceofNode.getParent();
return !(andNode != null
&& andNode.isAnd()
&& isUndefinedTypeofGuardFor(andNode.getFirstChild(), reference));
} else {
return false;
}
}
/**
* Is the expression of the form {@code x instanceof Ref}?
*
* @param expression
* @param reference Ref node must be equivalent to this node
*/
private boolean isInstanceofFor(Node expression, Node reference) {
return expression.isInstanceOf() && expression.getLastChild().isEquivalentTo(reference);
}
}