682 lines
19 KiB
JavaScript
682 lines
19 KiB
JavaScript
/* eslint max-len: 0 */
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import type NodePath from "babel-traverse";
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import type Scope from "babel-traverse";
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import type File from "../../../file";
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import traverse from "babel-traverse";
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import { visitor as tdzVisitor } from "./tdz";
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import * as t from "babel-types";
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import values from "lodash/object/values";
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import extend from "lodash/object/extend";
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import template from "babel-template";
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export default function () {
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return {
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visitor: {
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VariableDeclaration(path, file) {
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let { node, parent, scope } = path;
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if (!isBlockScoped(node)) return;
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convertBlockScopedToVar(path, parent, scope, true);
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if (node._tdzThis) {
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let nodes = [node];
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for (let i = 0; i < node.declarations.length; i++) {
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let decl = node.declarations[i];
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if (decl.init) {
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let assign = t.assignmentExpression("=", decl.id, decl.init);
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assign._ignoreBlockScopingTDZ = true;
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nodes.push(t.expressionStatement(assign));
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}
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decl.init = file.addHelper("temporalUndefined");
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}
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node._blockHoist = 2;
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if (path.isCompletionRecord()) {
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// ensure we don't break completion record semantics by returning
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// the initialiser of the last declarator
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nodes.push(t.expressionStatement(scope.buildUndefinedNode()));
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}
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path.replaceWithMultiple(nodes);
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}
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},
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Loop(path, file) {
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let { node, parent, scope } = path;
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t.ensureBlock(node);
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let blockScoping = new BlockScoping(path, path.get("body"), parent, scope, file);
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let replace = blockScoping.run();
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if (replace) path.replaceWith(replace);
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},
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"BlockStatement|Program"(path, file) {
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if (!t.isLoop(path.parent)) {
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let blockScoping = new BlockScoping(null, path, path.parent, path.scope, file);
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blockScoping.run();
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}
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}
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}
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};
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}
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let buildRetCheck = template(`
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if (typeof RETURN === "object") return RETURN.v;
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`);
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function isBlockScoped(node) {
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if (!t.isVariableDeclaration(node)) return false;
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if (node[t.BLOCK_SCOPED_SYMBOL]) return true;
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if (node.kind !== "let" && node.kind !== "const") return false;
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return true;
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}
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function convertBlockScopedToVar(path, parent, scope, moveBindingsToParent = false) {
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const { node } = path;
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// https://github.com/babel/babel/issues/255
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if (!t.isFor(parent)) {
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for (let i = 0; i < node.declarations.length; i++) {
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let declar = node.declarations[i];
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declar.init = declar.init || scope.buildUndefinedNode();
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}
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}
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node[t.BLOCK_SCOPED_SYMBOL] = true;
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node.kind = "var";
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// Move bindings from current block scope to function scope.
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if (moveBindingsToParent) {
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const parentScope = scope.getFunctionParent();
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const ids = path.getBindingIdentifiers();
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for (let name in ids) {
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let binding = scope.getOwnBinding(name);
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if (binding) binding.kind = "var";
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scope.moveBindingTo(name, parentScope);
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}
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}
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}
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function isVar(node) {
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return t.isVariableDeclaration(node, { kind: "var" }) && !isBlockScoped(node);
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}
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function replace(path, node, scope, remaps) {
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let remap = remaps[node.name];
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if (!remap) return;
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let ownBinding = scope.getBindingIdentifier(node.name);
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if (ownBinding === remap.binding) {
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scope.rename(node.name, remap.uid);
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} else {
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// scope already has it's own binding that doesn't
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// match the one we have a stored replacement for
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if (path) path.skip();
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}
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}
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let replaceVisitor = {
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ReferencedIdentifier(path, remaps) {
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replace(path, path.node, path.scope, remaps);
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},
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AssignmentExpression(path, remaps) {
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let ids = path.getBindingIdentifiers();
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for (let name in ids) {
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replace(null, ids[name], path.scope, remaps);
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}
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},
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};
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function traverseReplace(node, parent, scope, remaps) {
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if (t.isIdentifier(node)) {
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replace(node, parent, scope, remaps);
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}
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if (t.isAssignmentExpression(node)) {
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let ids = t.getBindingIdentifiers(node);
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for (let name in ids) {
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replace(ids[name], parent, scope, remaps);
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}
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}
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scope.traverse(node, replaceVisitor, remaps);
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}
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let letReferenceBlockVisitor = traverse.visitors.merge([{
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Function(path, state) {
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path.traverse(letReferenceFunctionVisitor, state);
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return path.skip();
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}
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}, tdzVisitor]);
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let letReferenceFunctionVisitor = traverse.visitors.merge([{
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ReferencedIdentifier(path, state) {
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let ref = state.letReferences[path.node.name];
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// not a part of our scope
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if (!ref) return;
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// this scope has a variable with the same name so it couldn't belong
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// to our let scope
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let localBinding = path.scope.getBindingIdentifier(path.node.name);
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if (localBinding && localBinding !== ref) return;
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state.closurify = true;
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}
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}, tdzVisitor]);
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let hoistVarDeclarationsVisitor = {
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enter(path, self) {
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let { node, parent } = path;
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if (path.isForStatement()) {
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if (isVar(node.init, node)) {
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let nodes = self.pushDeclar(node.init);
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if (nodes.length === 1) {
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node.init = nodes[0];
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} else {
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node.init = t.sequenceExpression(nodes);
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}
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}
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} else if (path.isFor()) {
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if (isVar(node.left, node)) {
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self.pushDeclar(node.left);
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node.left = node.left.declarations[0].id;
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}
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} else if (isVar(node, parent)) {
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path.replaceWithMultiple(self.pushDeclar(node).map((expr) => t.expressionStatement(expr)));
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} else if (path.isFunction()) {
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return path.skip();
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}
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}
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};
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let loopLabelVisitor = {
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LabeledStatement({ node }, state) {
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state.innerLabels.push(node.label.name);
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}
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};
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let continuationVisitor = {
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enter(path, state) {
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if (path.isAssignmentExpression() || path.isUpdateExpression()) {
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let bindings = path.getBindingIdentifiers();
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for (let name in bindings) {
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if (state.outsideReferences[name] !== path.scope.getBindingIdentifier(name)) continue;
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state.reassignments[name] = true;
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}
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}
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}
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};
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function loopNodeTo(node) {
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if (t.isBreakStatement(node)) {
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return "break";
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} else if (t.isContinueStatement(node)) {
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return "continue";
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}
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}
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let loopVisitor = {
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Loop(path, state) {
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let oldIgnoreLabeless = state.ignoreLabeless;
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state.ignoreLabeless = true;
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path.traverse(loopVisitor, state);
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state.ignoreLabeless = oldIgnoreLabeless;
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path.skip();
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},
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Function(path) {
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path.skip();
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},
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SwitchCase(path, state) {
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let oldInSwitchCase = state.inSwitchCase;
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state.inSwitchCase = true;
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path.traverse(loopVisitor, state);
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state.inSwitchCase = oldInSwitchCase;
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path.skip();
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},
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"BreakStatement|ContinueStatement|ReturnStatement"(path, state) {
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let { node, parent, scope } = path;
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if (node[this.LOOP_IGNORE]) return;
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let replace;
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let loopText = loopNodeTo(node);
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if (loopText) {
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if (node.label) {
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// we shouldn't be transforming this because it exists somewhere inside
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if (state.innerLabels.indexOf(node.label.name) >= 0) {
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return;
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}
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loopText = `${loopText}|${node.label.name}`;
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} else {
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// we shouldn't be transforming these statements because
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// they don't refer to the actual loop we're scopifying
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if (state.ignoreLabeless) return;
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//
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if (state.inSwitchCase) return;
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// break statements mean something different in this context
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if (t.isBreakStatement(node) && t.isSwitchCase(parent)) return;
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}
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state.hasBreakContinue = true;
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state.map[loopText] = node;
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replace = t.stringLiteral(loopText);
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}
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if (path.isReturnStatement()) {
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state.hasReturn = true;
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replace = t.objectExpression([
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t.objectProperty(t.identifier("v"), node.argument || scope.buildUndefinedNode())
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]);
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}
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if (replace) {
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replace = t.returnStatement(replace);
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replace[this.LOOP_IGNORE] = true;
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path.skip();
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path.replaceWith(t.inherits(replace, node));
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}
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}
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};
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class BlockScoping {
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constructor(loopPath?: NodePath, blockPath: NodePath, parent: Object, scope: Scope, file: File) {
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this.parent = parent;
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this.scope = scope;
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this.file = file;
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this.blockPath = blockPath;
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this.block = blockPath.node;
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this.outsideLetReferences = Object.create(null);
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this.hasLetReferences = false;
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this.letReferences = Object.create(null);
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this.body = [];
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if (loopPath) {
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this.loopParent = loopPath.parent;
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this.loopLabel = t.isLabeledStatement(this.loopParent) && this.loopParent.label;
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this.loopPath = loopPath;
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this.loop = loopPath.node;
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}
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}
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/**
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* Start the ball rolling.
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*/
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run() {
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let block = this.block;
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if (block._letDone) return;
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block._letDone = true;
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let needsClosure = this.getLetReferences();
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// this is a block within a `Function/Program` so we can safely leave it be
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if (t.isFunction(this.parent) || t.isProgram(this.block)) {
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this.updateScopeInfo();
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return;
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}
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// we can skip everything
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if (!this.hasLetReferences) return;
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if (needsClosure) {
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this.wrapClosure();
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} else {
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this.remap();
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}
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this.updateScopeInfo();
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if (this.loopLabel && !t.isLabeledStatement(this.loopParent)) {
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return t.labeledStatement(this.loopLabel, this.loop);
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}
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}
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updateScopeInfo() {
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let scope = this.scope;
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let parentScope = scope.getFunctionParent();
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let letRefs = this.letReferences;
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for (let key in letRefs) {
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let ref = letRefs[key];
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const binding = scope.getBinding(ref.name);
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if (!binding) continue;
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if (binding.kind === "let" || binding.kind === "const") {
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binding.kind = "var";
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scope.moveBindingTo(ref.name, parentScope);
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}
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}
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}
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remap() {
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let hasRemaps = false;
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let letRefs = this.letReferences;
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let scope = this.scope;
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// alright, so since we aren't wrapping this block in a closure
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// we have to check if any of our let variables collide with
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// those in upper scopes and then if they do, generate a uid
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// for them and replace all references with it
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let remaps = Object.create(null);
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for (let key in letRefs) {
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// just an Identifier node we collected in `getLetReferences`
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// this is the defining identifier of a declaration
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let ref = letRefs[key];
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// todo: could skip this if the colliding binding is in another function
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if (scope.parentHasBinding(key) || scope.hasGlobal(key)) {
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let uid = scope.generateUidIdentifier(ref.name).name;
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ref.name = uid;
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hasRemaps = true;
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remaps[key] = remaps[uid] = {
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binding: ref,
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uid: uid
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};
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}
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}
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if (!hasRemaps) return;
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//
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let loop = this.loop;
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if (loop) {
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traverseReplace(loop.right, loop, scope, remaps);
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traverseReplace(loop.test, loop, scope, remaps);
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traverseReplace(loop.update, loop, scope, remaps);
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}
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this.blockPath.traverse(replaceVisitor, remaps);
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}
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wrapClosure() {
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let block = this.block;
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let outsideRefs = this.outsideLetReferences;
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// remap loop heads with colliding variables
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if (this.loop) {
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for (let name in outsideRefs) {
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let id = outsideRefs[name];
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if (this.scope.hasGlobal(id.name) || this.scope.parentHasBinding(id.name)) {
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delete outsideRefs[id.name];
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delete this.letReferences[id.name];
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this.scope.rename(id.name);
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this.letReferences[id.name] = id;
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outsideRefs[id.name] = id;
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}
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}
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}
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// if we're inside of a for loop then we search to see if there are any
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// `break`s, `continue`s, `return`s etc
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this.has = this.checkLoop();
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// hoist let references to retain scope
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this.hoistVarDeclarations();
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// turn outsideLetReferences into an array
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let params = values(outsideRefs);
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let args = values(outsideRefs);
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// build the closure that we're going to wrap the block with
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let fn = t.functionExpression(null, params, t.blockStatement(block.body));
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fn.shadow = true;
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// continuation
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this.addContinuations(fn);
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// replace the current block body with the one we're going to build
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block.body = this.body;
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let ref = fn;
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if (this.loop) {
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ref = this.scope.generateUidIdentifier("loop");
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this.loopPath.insertBefore(t.variableDeclaration("var", [
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t.variableDeclarator(ref, fn)
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]));
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}
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// build a call and a unique id that we can assign the return value to
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let call = t.callExpression(ref, args);
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let ret = this.scope.generateUidIdentifier("ret");
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// handle generators
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let hasYield = traverse.hasType(fn.body, this.scope, "YieldExpression", t.FUNCTION_TYPES);
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if (hasYield) {
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fn.generator = true;
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call = t.yieldExpression(call, true);
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}
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// handlers async functions
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let hasAsync = traverse.hasType(fn.body, this.scope, "AwaitExpression", t.FUNCTION_TYPES);
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if (hasAsync) {
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fn.async = true;
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call = t.awaitExpression(call);
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}
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this.buildClosure(ret, call);
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}
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/**
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* Push the closure to the body.
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*/
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buildClosure(ret: { type: "Identifier" }, call: { type: "CallExpression" }) {
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let has = this.has;
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if (has.hasReturn || has.hasBreakContinue) {
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this.buildHas(ret, call);
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} else {
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this.body.push(t.expressionStatement(call));
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}
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}
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/**
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* If any of the outer let variables are reassigned then we need to rename them in
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* the closure so we can get direct access to the outer variable to continue the
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* iteration with bindings based on each iteration.
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*
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* Reference: https://github.com/babel/babel/issues/1078
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*/
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addContinuations(fn) {
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let state = {
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reassignments: {},
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outsideReferences: this.outsideLetReferences
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};
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this.scope.traverse(fn, continuationVisitor, state);
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for (let i = 0; i < fn.params.length; i++) {
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let param = fn.params[i];
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if (!state.reassignments[param.name]) continue;
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let newParam = this.scope.generateUidIdentifier(param.name);
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fn.params[i] = newParam;
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this.scope.rename(param.name, newParam.name, fn);
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// assign outer reference as it's been modified internally and needs to be retained
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fn.body.body.push(t.expressionStatement(t.assignmentExpression("=", param, newParam)));
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}
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}
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getLetReferences() {
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let block = this.block;
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let declarators = [];
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if (this.loop) {
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let init = this.loop.left || this.loop.init;
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if (isBlockScoped(init)) {
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declarators.push(init);
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extend(this.outsideLetReferences, t.getBindingIdentifiers(init));
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}
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}
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//
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if (block.body) {
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for (let i = 0; i < block.body.length; i++) {
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let declar = block.body[i];
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if (t.isClassDeclaration(declar) || t.isFunctionDeclaration(declar) || isBlockScoped(declar)) {
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let declarPath = this.blockPath.get("body")[i];
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if (isBlockScoped(declar)) {
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convertBlockScopedToVar(declarPath, block, this.scope);
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}
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declarators = declarators.concat(declar.declarations || declar);
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}
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}
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}
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//
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for (let i = 0; i < declarators.length; i++) {
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let declar = declarators[i];
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let keys = t.getBindingIdentifiers(declar);
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extend(this.letReferences, keys);
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this.hasLetReferences = true;
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}
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// no let references so we can just quit
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if (!this.hasLetReferences) return;
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let state = {
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letReferences: this.letReferences,
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closurify: false,
|
|
file: this.file
|
|
};
|
|
|
|
// traverse through this block, stopping on functions and checking if they
|
|
// contain any local let references
|
|
this.blockPath.traverse(letReferenceBlockVisitor, state);
|
|
|
|
return state.closurify;
|
|
}
|
|
|
|
/**
|
|
* If we're inside of a loop then traverse it and check if it has one of
|
|
* the following node types `ReturnStatement`, `BreakStatement`,
|
|
* `ContinueStatement` and replace it with a return value that we can track
|
|
* later on.
|
|
*/
|
|
|
|
checkLoop(): Object {
|
|
let state = {
|
|
hasBreakContinue: false,
|
|
ignoreLabeless: false,
|
|
inSwitchCase: false,
|
|
innerLabels: [],
|
|
hasReturn: false,
|
|
isLoop: !!this.loop,
|
|
map: {},
|
|
LOOP_IGNORE: Symbol()
|
|
};
|
|
|
|
this.blockPath.traverse(loopLabelVisitor, state);
|
|
this.blockPath.traverse(loopVisitor, state);
|
|
|
|
return state;
|
|
}
|
|
|
|
/**
|
|
* Hoist all let declarations in this block to before it so they retain scope
|
|
* once we wrap everything in a closure.
|
|
*/
|
|
|
|
hoistVarDeclarations() {
|
|
this.blockPath.traverse(hoistVarDeclarationsVisitor, this);
|
|
}
|
|
|
|
/**
|
|
* Turn a `VariableDeclaration` into an array of `AssignmentExpressions` with
|
|
* their declarations hoisted to before the closure wrapper.
|
|
*/
|
|
|
|
pushDeclar(node: { type: "VariableDeclaration" }): Array<Object> {
|
|
let declars = [];
|
|
let names = t.getBindingIdentifiers(node);
|
|
for (let name in names) {
|
|
declars.push(t.variableDeclarator(names[name]));
|
|
}
|
|
|
|
this.body.push(t.variableDeclaration(node.kind, declars));
|
|
|
|
let replace = [];
|
|
|
|
for (let i = 0; i < node.declarations.length; i++) {
|
|
let declar = node.declarations[i];
|
|
if (!declar.init) continue;
|
|
|
|
let expr = t.assignmentExpression("=", declar.id, declar.init);
|
|
replace.push(t.inherits(expr, declar));
|
|
}
|
|
|
|
return replace;
|
|
}
|
|
|
|
buildHas(ret: { type: "Identifier" }, call: { type: "CallExpression" }) {
|
|
let body = this.body;
|
|
|
|
body.push(t.variableDeclaration("var", [
|
|
t.variableDeclarator(ret, call)
|
|
]));
|
|
|
|
let retCheck;
|
|
let has = this.has;
|
|
let cases = [];
|
|
|
|
if (has.hasReturn) {
|
|
// typeof ret === "object"
|
|
retCheck = buildRetCheck({
|
|
RETURN: ret
|
|
});
|
|
}
|
|
|
|
if (has.hasBreakContinue) {
|
|
for (let key in has.map) {
|
|
cases.push(t.switchCase(t.stringLiteral(key), [has.map[key]]));
|
|
}
|
|
|
|
if (has.hasReturn) {
|
|
cases.push(t.switchCase(null, [retCheck]));
|
|
}
|
|
|
|
if (cases.length === 1) {
|
|
let single = cases[0];
|
|
body.push(t.ifStatement(
|
|
t.binaryExpression("===", ret, single.test),
|
|
single.consequent[0]
|
|
));
|
|
} else {
|
|
// https://github.com/babel/babel/issues/998
|
|
for (let i = 0; i < cases.length; i++) {
|
|
let caseConsequent = cases[i].consequent[0];
|
|
if (t.isBreakStatement(caseConsequent) && !caseConsequent.label) {
|
|
caseConsequent.label = this.loopLabel = this.loopLabel || this.scope.generateUidIdentifier("loop");
|
|
}
|
|
}
|
|
|
|
body.push(t.switchStatement(ret, cases));
|
|
}
|
|
} else {
|
|
if (has.hasReturn) {
|
|
body.push(retCheck);
|
|
}
|
|
}
|
|
}
|
|
}
|