export default function () {
return {
visitor: {
VariableDeclaration(path, file) {
let { node, parent, scope } = path;
if (!isBlockScoped(node)) return;
convertBlockScopedToVar(path, null, parent, scope, true);
if (node._tdzThis) {
let nodes = [node];
for (let i = 0; i < node.declarations.length; i++) {
let decl = node.declarations[i];
if (decl.init) {
let assign = t.assignmentExpression("=", decl.id, decl.init);
assign._ignoreBlockScopingTDZ = true;
nodes.push(t.expressionStatement(assign));
}
decl.init = file.addHelper("temporalUndefined");
}
node._blockHoist = 2;
if (path.isCompletionRecord()) {
// ensure we don't break completion record semantics by returning
// the initialiser of the last declarator
nodes.push(t.expressionStatement(scope.buildUndefinedNode()));
}
path.replaceWithMultiple(nodes);
}
},
Loop(path, file) {
let { node, parent, scope } = path;
t.ensureBlock(node);
let blockScoping = new BlockScoping(path, path.get("body"), parent, scope, file);
let replace = blockScoping.run();
if (replace) path.replaceWith(replace);
},
CatchClause(path, file) {
let { parent, scope } = path;
let blockScoping = new BlockScoping(null, path.get("body"), parent, scope, file);
blockScoping.run();
},
"BlockStatement|SwitchStatement|Program"(path, file) {
if (!ignoreBlock(path)) {
let blockScoping = new BlockScoping(null, path, path.parent, path.scope, file);
blockScoping.run();
}
}
}
};
}
push(opts: {
id: Object;
init: ?Object;
unique: ?boolean;
_blockHoist: ?number;
kind: "var" | "let";
}) {
let path = this.path;
if (!path.isBlockStatement() && !path.isProgram()) {
path = this.getBlockParent().path;
}
if (path.isSwitchStatement()) {
path = this.getFunctionParent().path;
}
if (path.isLoop() || path.isCatchClause() || path.isFunction()) {
t.ensureBlock(path.node);
path = path.get("body");
}
let unique = opts.unique;
let kind = opts.kind || "var";
let blockHoist = opts._blockHoist == null ? 2 : opts._blockHoist;
let dataKey = `declaration:${kind}:${blockHoist}`;
let declarPath = !unique && path.getData(dataKey);
if (!declarPath) {
let declar = t.variableDeclaration(kind, []);
declar._generated = true;
declar._blockHoist = blockHoist;
[declarPath] = path.unshiftContainer("body", [declar]);
if (!unique) path.setData(dataKey, declarPath);
}
let declarator = t.variableDeclarator(opts.id, opts.init);
declarPath.node.declarations.push(declarator);
this.registerBinding(kind, declarPath.get("declarations").pop());
}
export function ensureBlock() {
return t.ensureBlock(this.node);
}