optimise and clean up es6.tailCall transformer
This commit is contained in:
Sebastian McKenzie
parent
2a78ae9889
commit
faade72787
@ -1,3 +1,4 @@
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import blockScopedFunctions from "../spec/block-scoped-functions";
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import reduceRight from "lodash/collection/reduceRight";
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import * as messages from "../../../messages";
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import flatten from "lodash/array/flatten";
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@ -21,7 +22,7 @@ function returnBlock(expr) {
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}
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// looks for and replaces tail recursion calls
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var firstPass = {
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var visitor = {
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enter(node, parent, scope, state) {
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if (t.isTryStatement(parent)) {
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if (node === parent.block) {
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@ -33,7 +34,6 @@ var firstPass = {
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},
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ReturnStatement(node, parent, scope, state) {
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this.skip();
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return state.subTransform(node.argument);
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},
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@ -42,46 +42,18 @@ var firstPass = {
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},
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VariableDeclaration(node, parent, scope, state) {
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this.skip();
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state.vars.push(node);
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}
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};
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},
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// hoists up function declarations, replaces `this` and `arguments` and marks
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// them as needed
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var secondPass = {
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ThisExpression(node, parent, scope, state) {
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state.needsThis = true;
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return state.getThisId();
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state.thises.push(this);
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},
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ReferencedIdentifier(node, parent, scope, state) {
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if (node.name !== "arguments") return;
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state.needsArguments = true;
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return state.getArgumentsId();
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},
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Function(node, parent, scope, state) {
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this.skip();
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if (this.isFunctionDeclaration()) {
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node = t.variableDeclaration("var", [
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t.variableDeclarator(node.id, t.toExpression(node))
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]);
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node._blockHoist = 2;
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return node;
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}
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}
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};
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// optimizes recursion by removing `this` and `arguments` if they aren't used
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var thirdPass = {
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AssignmentExpression(node, parent, scope, state) {
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if (!state.needsThis && node.left === state.getThisId()) {
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this.remove();
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} else if (!state.needsArguments && node.left === state.getArgumentsId() && t.isArrayExpression(node.right)) {
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return map(node.right.elements, function (elem) {
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return t.expressionStatement(elem);
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});
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if (node.name === "arguments") {
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state.needsArguments = true;
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state.arguments.push(this);
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}
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}
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};
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@ -89,11 +61,16 @@ var thirdPass = {
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class TailCallTransformer {
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constructor(path, scope, file) {
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this.hasTailRecursion = false;
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this.needsArguments = false;
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this.setsArguments = false;
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this.needsThis = false;
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this.ownerId = path.node.id;
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this.vars = [];
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this.needsArguments = false;
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this.setsArguments = false;
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this.arguments = [];
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this.needsThis = false;
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this.thises = [];
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this.ownerId = path.node.id;
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this.vars = [];
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this.scope = scope;
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this.path = path;
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@ -159,10 +136,12 @@ class TailCallTransformer {
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if (!ownerId) return;
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// traverse the function and look for tail recursion
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this.path.traverse(firstPass, this);
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this.path.traverse(visitor, this);
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// has no tail call recursion
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if (!this.hasTailRecursion) return;
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// the function binding isn't constant so we can't be sure that it's the same function :(
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if (this.hasDeopt()) {
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this.file.log.deopt(node, messages.get("tailCallReassignmentDeopt"));
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return;
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@ -170,14 +149,18 @@ class TailCallTransformer {
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//
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this.path.traverse(secondPass, this);
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if (!this.needsThis || !this.needsArguments) {
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this.path.traverse(thirdPass, this);
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}
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var body = t.ensureBlock(node).body;
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for (var i = 0; i < body.length; i++) {
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var bodyNode = body[i];
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if (!t.isFunctionDeclaration(bodyNode)) continue;
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bodyNode = body[i] = t.variableDeclaration("var", [
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t.variableDeclarator(bodyNode.id, t.toExpression(bodyNode))
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]);
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bodyNode._blockHoist = 2;
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}
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if (this.vars.length > 0) {
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var declarations = flatten(map(this.vars, function (decl) {
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return decl.declarations;
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@ -204,22 +187,28 @@ class TailCallTransformer {
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);
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node.body = util.template("tail-call-body", {
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AGAIN_ID: this.getAgainId(),
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THIS_ID: this.thisId,
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ARGUMENTS_ID: this.argumentsId,
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FUNCTION_ID: this.getFunctionId(),
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BLOCK: node.body
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FUNCTION_ID: this.getFunctionId(),
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AGAIN_ID: this.getAgainId(),
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BLOCK: node.body
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});
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var topVars = [];
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if (this.needsThis) {
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for (var path of (this.thises: Array)) {
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path.replaceWith(this.getThisId());
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}
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topVars.push(t.variableDeclarator(this.getThisId(), t.thisExpression()));
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}
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if (this.needsArguments || this.setsArguments) {
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var decl = t.variableDeclarator(this.getArgumentsId());
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if (this.needsArguments) {
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for (var path of (this.arguments: Array)) {
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path.replaceWith(this.argumentsId);
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}
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var decl = t.variableDeclarator(this.argumentsId);
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if (this.argumentsId) {
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decl.init = t.identifier("arguments");
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}
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topVars.push(decl);
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@ -332,7 +321,7 @@ class TailCallTransformer {
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var body = [];
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if (!t.isThisExpression(thisBinding)) {
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if (this.needsThis && !t.isThisExpression(thisBinding)) {
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body.push(t.expressionStatement(t.assignmentExpression(
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"=",
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this.getThisId(),
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@ -345,29 +334,35 @@ class TailCallTransformer {
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}
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var argumentsId = this.getArgumentsId();
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var params = this.getParams();
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var params = this.getParams();
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body.push(t.expressionStatement(t.assignmentExpression(
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"=",
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argumentsId,
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args
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)));
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var i, param;
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if (this.needsArguments) {
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body.push(t.expressionStatement(t.assignmentExpression(
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"=",
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argumentsId,
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args
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)));
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}
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if (t.isArrayExpression(args)) {
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var elems = args.elements;
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for (i = 0; i < elems.length && i < params.length; i++) {
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param = params[i];
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for (let i = 0; i < elems.length && i < params.length; i++) {
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let param = params[i];
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var elem = elems[i] || (elems[i] = t.identifier("undefined"));
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if (!param._isDefaultPlaceholder) {
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elems[i] = t.assignmentExpression("=", param, elem);
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}
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}
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if (!this.needsArguments) {
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for (var elem of (elems: Array)) {
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body.push(t.expressionStatement(elem));
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}
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}
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} else {
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this.setsArguments = true;
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for (i = 0; i < params.length; i++) {
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param = params[i];
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for (let i = 0; i < params.length; i++) {
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let param = params[i];
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if (!param._isDefaultPlaceholder) {
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body.push(t.expressionStatement(t.assignmentExpression(
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"=",
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@ -381,6 +376,7 @@ class TailCallTransformer {
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body.push(t.expressionStatement(
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t.assignmentExpression("=", this.getAgainId(), t.literal(true))
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));
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body.push(t.continueStatement(this.getFunctionId()));
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return body;
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