JSModule getRefModule(ReferenceCollectingCallback.Reference ref) {
CompilerInput input = compiler.getInput(ref.getInputId());
return input == null ? null : input.getModule();
}
private boolean inlineAliasIfPossible(Name name, Ref alias, GlobalNamespace namespace) {
// Ensure that the alias is assigned to a local variable at that
// variable's declaration. If the alias's parent is a NAME,
// then the NAME must be the child of a VAR node, and we must
// be in a VAR assignment.
Node aliasParent = alias.node.getParent();
if (aliasParent.isName()) {
// Ensure that the local variable is well defined and never reassigned.
Scope scope = alias.scope;
String aliasVarName = aliasParent.getString();
Var aliasVar = scope.getVar(aliasVarName);
ReferenceCollectingCallback collector =
new ReferenceCollectingCallback(
compiler,
ReferenceCollectingCallback.DO_NOTHING_BEHAVIOR,
Predicates.equalTo(aliasVar));
collector.processScope(scope);
ReferenceCollection aliasRefs = collector.getReferences(aliasVar);
Set<AstChange> newNodes = new LinkedHashSet<>();
if (aliasRefs.isWellDefined() && aliasRefs.firstReferenceIsAssigningDeclaration()) {
if (!aliasRefs.isAssignedOnceInLifetime()) {
// Static properties of constructors are always collapsed.
// So, if a constructor is aliased and its properties are accessed from
// the alias, we would like to inline the alias here to access the
// properties correctly.
// But if the aliased variable is assigned more than once, we can't
// inline, so we warn.
if (name.isConstructor()) {
boolean accessPropsAfterAliasing = false;
for (Reference ref : aliasRefs.references) {
if (ref.getNode().getParent().isGetProp()) {
accessPropsAfterAliasing = true;
break;
}
}
if (accessPropsAfterAliasing) {
compiler.report(JSError.make(aliasParent, UNSAFE_CTOR_ALIASING, aliasVarName));
}
}
return false;
}
// The alias is well-formed, so do the inlining now.
int size = aliasRefs.references.size();
for (int i = 1; i < size; i++) {
ReferenceCollectingCallback.Reference aliasRef = aliasRefs.references.get(i);
Node newNode = alias.node.cloneTree();
aliasRef.getParent().replaceChild(aliasRef.getNode(), newNode);
newNodes.add(new AstChange(getRefModule(aliasRef), aliasRef.getScope(), newNode));
}
// just set the original alias to null.
aliasParent.replaceChild(alias.node, IR.nullNode());
compiler.reportCodeChange();
// Inlining the variable may have introduced new references
// to descendants of {@code name}. So those need to be collected now.
namespace.scanNewNodes(newNodes);
return true;
}
}
return false;
}