Add rollup-plugin-minify-html-template-literals to node_modules

R=jacktfranklin@chromium.org

Bug: 1213034
Change-Id: I5da8225f60b53870a1c67d6b5d02a464c08f4eb2
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/2917088
Commit-Queue: Tim van der Lippe <tvanderlippe@chromium.org>
Reviewed-by: Jack Franklin <jacktfranklin@chromium.org>
diff --git a/node_modules/uglify-js/lib/ast.js b/node_modules/uglify-js/lib/ast.js
new file mode 100644
index 0000000..590c09b
--- /dev/null
+++ b/node_modules/uglify-js/lib/ast.js
@@ -0,0 +1,2064 @@
+/***********************************************************************
+
+  A JavaScript tokenizer / parser / beautifier / compressor.
+  https://github.com/mishoo/UglifyJS
+
+  -------------------------------- (C) ---------------------------------
+
+                           Author: Mihai Bazon
+                         <mihai.bazon@gmail.com>
+                       http://mihai.bazon.net/blog
+
+  Distributed under the BSD license:
+
+    Copyright 2012 (c) Mihai Bazon <mihai.bazon@gmail.com>
+
+    Redistribution and use in source and binary forms, with or without
+    modification, are permitted provided that the following conditions
+    are met:
+
+        * Redistributions of source code must retain the above
+          copyright notice, this list of conditions and the following
+          disclaimer.
+
+        * Redistributions in binary form must reproduce the above
+          copyright notice, this list of conditions and the following
+          disclaimer in the documentation and/or other materials
+          provided with the distribution.
+
+    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER “AS IS” AND ANY
+    EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+    IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+    PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER BE
+    LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
+    OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+    PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+    PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+    THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR
+    TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
+    THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+    SUCH DAMAGE.
+
+ ***********************************************************************/
+
+"use strict";
+
+function DEFNODE(type, props, methods, base) {
+    if (typeof base === "undefined") base = AST_Node;
+    props = props ? props.split(/\s+/) : [];
+    var self_props = props;
+    if (base && base.PROPS) props = props.concat(base.PROPS);
+    var code = [
+        "return function AST_", type, "(props){",
+        "if(props){",
+    ];
+    props.forEach(function(prop) {
+        code.push("this.", prop, "=props.", prop, ";");
+    });
+    code.push("}");
+    var proto = base && new base;
+    if (proto && proto.initialize || methods && methods.initialize) code.push("this.initialize();");
+    code.push("}");
+    var ctor = new Function(code.join(""))();
+    if (proto) {
+        ctor.prototype = proto;
+        ctor.BASE = base;
+    }
+    if (base) base.SUBCLASSES.push(ctor);
+    ctor.prototype.CTOR = ctor;
+    ctor.PROPS = props || null;
+    ctor.SELF_PROPS = self_props;
+    ctor.SUBCLASSES = [];
+    if (type) {
+        ctor.prototype.TYPE = ctor.TYPE = type;
+    }
+    if (methods) for (var name in methods) if (HOP(methods, name)) {
+        if (/^\$/.test(name)) {
+            ctor[name.substr(1)] = methods[name];
+        } else {
+            ctor.prototype[name] = methods[name];
+        }
+    }
+    ctor.DEFMETHOD = function(name, method) {
+        this.prototype[name] = method;
+    };
+    if (typeof exports !== "undefined") {
+        exports["AST_" + type] = ctor;
+    }
+    return ctor;
+}
+
+var AST_Token = DEFNODE("Token", "type value line col pos endline endcol endpos nlb comments_before comments_after file raw", {
+}, null);
+
+var AST_Node = DEFNODE("Node", "start end", {
+    _clone: function(deep) {
+        if (deep) {
+            var self = this.clone();
+            return self.transform(new TreeTransformer(function(node) {
+                if (node !== self) {
+                    return node.clone(true);
+                }
+            }));
+        }
+        return new this.CTOR(this);
+    },
+    clone: function(deep) {
+        return this._clone(deep);
+    },
+    $documentation: "Base class of all AST nodes",
+    $propdoc: {
+        start: "[AST_Token] The first token of this node",
+        end: "[AST_Token] The last token of this node"
+    },
+    walk: function(visitor) {
+        visitor.visit(this);
+    },
+    _validate: function() {
+        if (this.TYPE == "Node") throw new Error("should not instantiate AST_Node");
+    },
+    validate: function() {
+        var ctor = this.CTOR;
+        do {
+            ctor.prototype._validate.call(this);
+        } while (ctor = ctor.BASE);
+    },
+    validate_ast: function() {
+        var marker = {};
+        this.walk(new TreeWalker(function(node) {
+            if (node.validate_visited === marker) {
+                throw new Error(string_template("cannot reuse {type} from [{file}:{line},{col}]", {
+                    type: "AST_" + node.TYPE,
+                    file: node.start.file,
+                    line: node.start.line,
+                    col: node.start.col,
+                }));
+            }
+            node.validate_visited = marker;
+        }));
+    },
+}, null);
+
+(AST_Node.log_function = function(fn, verbose) {
+    if (typeof fn != "function") {
+        AST_Node.info = AST_Node.warn = noop;
+        return;
+    }
+    var printed = Object.create(null);
+    AST_Node.info = verbose ? function(text, props) {
+        log("INFO: " + string_template(text, props));
+    } : noop;
+    AST_Node.warn = function(text, props) {
+        log("WARN: " + string_template(text, props));
+    };
+
+    function log(msg) {
+        if (printed[msg]) return;
+        printed[msg] = true;
+        fn(msg);
+    }
+})();
+
+var restore_transforms = [];
+AST_Node.enable_validation = function() {
+    AST_Node.disable_validation();
+    (function validate_transform(ctor) {
+        ctor.SUBCLASSES.forEach(validate_transform);
+        if (!HOP(ctor.prototype, "transform")) return;
+        var transform = ctor.prototype.transform;
+        ctor.prototype.transform = function(tw, in_list) {
+            var node = transform.call(this, tw, in_list);
+            if (node instanceof AST_Node) {
+                node.validate();
+            } else if (!(node === null || in_list && List.is_op(node))) {
+                throw new Error("invalid transformed value: " + node);
+            }
+            return node;
+        };
+        restore_transforms.push(function() {
+            ctor.prototype.transform = transform;
+        });
+    })(this);
+};
+
+AST_Node.disable_validation = function() {
+    var restore;
+    while (restore = restore_transforms.pop()) restore();
+};
+
+/* -----[ statements ]----- */
+
+var AST_Statement = DEFNODE("Statement", null, {
+    $documentation: "Base class of all statements",
+    _validate: function() {
+        if (this.TYPE == "Statement") throw new Error("should not instantiate AST_Statement");
+    },
+});
+
+var AST_Debugger = DEFNODE("Debugger", null, {
+    $documentation: "Represents a debugger statement",
+}, AST_Statement);
+
+var AST_Directive = DEFNODE("Directive", "quote value", {
+    $documentation: "Represents a directive, like \"use strict\";",
+    $propdoc: {
+        quote: "[string?] the original quote character",
+        value: "[string] The value of this directive as a plain string (it's not an AST_String!)",
+    },
+    _validate: function() {
+        if (this.quote != null) {
+            if (typeof this.quote != "string") throw new Error("quote must be string");
+            if (!/^["']$/.test(this.quote)) throw new Error("invalid quote: " + this.quote);
+        }
+        if (typeof this.value != "string") throw new Error("value must be string");
+    },
+}, AST_Statement);
+
+var AST_EmptyStatement = DEFNODE("EmptyStatement", null, {
+    $documentation: "The empty statement (empty block or simply a semicolon)"
+}, AST_Statement);
+
+function is_statement(node) {
+    return node instanceof AST_Statement
+        && !(node instanceof AST_ClassExpression)
+        && !(node instanceof AST_LambdaExpression);
+}
+
+function validate_expression(value, prop, multiple, allow_spread, allow_hole) {
+    multiple = multiple ? "contain" : "be";
+    if (!(value instanceof AST_Node)) throw new Error(prop + " must " + multiple + " AST_Node");
+    if (value instanceof AST_DefaultValue) throw new Error(prop + " cannot " + multiple + " AST_DefaultValue");
+    if (value instanceof AST_Destructured) throw new Error(prop + " cannot " + multiple + " AST_Destructured");
+    if (value instanceof AST_Hole && !allow_hole) throw new Error(prop + " cannot " + multiple + " AST_Hole");
+    if (value instanceof AST_Spread && !allow_spread) throw new Error(prop + " cannot " + multiple + " AST_Spread");
+    if (is_statement(value)) throw new Error(prop + " cannot " + multiple + " AST_Statement");
+    if (value instanceof AST_SymbolDeclaration) {
+        throw new Error(prop + " cannot " + multiple + " AST_SymbolDeclaration");
+    }
+}
+
+function must_be_expression(node, prop) {
+    validate_expression(node[prop], prop);
+}
+
+var AST_SimpleStatement = DEFNODE("SimpleStatement", "body", {
+    $documentation: "A statement consisting of an expression, i.e. a = 1 + 2",
+    $propdoc: {
+        body: "[AST_Node] an expression node (should not be instanceof AST_Statement)",
+    },
+    walk: function(visitor) {
+        var node = this;
+        visitor.visit(node, function() {
+            node.body.walk(visitor);
+        });
+    },
+    _validate: function() {
+        must_be_expression(this, "body");
+    },
+}, AST_Statement);
+
+var AST_BlockScope = DEFNODE("BlockScope", "enclosed functions make_def parent_scope variables", {
+    $documentation: "Base class for all statements introducing a lexical scope",
+    $propdoc: {
+        enclosed: "[SymbolDef*/S] a list of all symbol definitions that are accessed from this scope or any subscopes",
+        functions: "[Dictionary/S] like `variables`, but only lists function declarations",
+        parent_scope: "[AST_Scope?/S] link to the parent scope",
+        variables: "[Dictionary/S] a map of name ---> SymbolDef for all variables/functions defined in this scope",
+    },
+    clone: function(deep) {
+        var node = this._clone(deep);
+        if (this.enclosed) node.enclosed = this.enclosed.slice();
+        if (this.functions) node.functions = this.functions.clone();
+        if (this.variables) node.variables = this.variables.clone();
+        return node;
+    },
+    pinned: function() {
+        return this.resolve().pinned();
+    },
+    resolve: function() {
+        return this.parent_scope.resolve();
+    },
+    _validate: function() {
+        if (this.TYPE == "BlockScope") throw new Error("should not instantiate AST_BlockScope");
+        if (this.parent_scope == null) return;
+        if (!(this.parent_scope instanceof AST_BlockScope)) throw new Error("parent_scope must be AST_BlockScope");
+        if (!(this.resolve() instanceof AST_Scope)) throw new Error("must be contained within AST_Scope");
+    },
+}, AST_Statement);
+
+function walk_body(node, visitor) {
+    node.body.forEach(function(node) {
+        node.walk(visitor);
+    });
+}
+
+var AST_Block = DEFNODE("Block", "body", {
+    $documentation: "A body of statements (usually braced)",
+    $propdoc: {
+        body: "[AST_Statement*] an array of statements"
+    },
+    walk: function(visitor) {
+        var node = this;
+        visitor.visit(node, function() {
+            walk_body(node, visitor);
+        });
+    },
+    _validate: function() {
+        if (this.TYPE == "Block") throw new Error("should not instantiate AST_Block");
+        this.body.forEach(function(node) {
+            if (!is_statement(node)) throw new Error("body must contain AST_Statement");
+        });
+    },
+}, AST_BlockScope);
+
+var AST_BlockStatement = DEFNODE("BlockStatement", null, {
+    $documentation: "A block statement",
+}, AST_Block);
+
+var AST_StatementWithBody = DEFNODE("StatementWithBody", "body", {
+    $documentation: "Base class for all statements that contain one nested body: `For`, `ForIn`, `Do`, `While`, `With`",
+    $propdoc: {
+        body: "[AST_Statement] the body; this should always be present, even if it's an AST_EmptyStatement"
+    },
+    _validate: function() {
+        if (this.TYPE == "StatementWithBody") throw new Error("should not instantiate AST_StatementWithBody");
+        if (!is_statement(this.body)) throw new Error("body must be AST_Statement");
+    },
+}, AST_BlockScope);
+
+var AST_LabeledStatement = DEFNODE("LabeledStatement", "label", {
+    $documentation: "Statement with a label",
+    $propdoc: {
+        label: "[AST_Label] a label definition"
+    },
+    walk: function(visitor) {
+        var node = this;
+        visitor.visit(node, function() {
+            node.label.walk(visitor);
+            node.body.walk(visitor);
+        });
+    },
+    clone: function(deep) {
+        var node = this._clone(deep);
+        if (deep) {
+            var label = node.label;
+            var def = this.label;
+            node.walk(new TreeWalker(function(node) {
+                if (node instanceof AST_LoopControl) {
+                    if (!node.label || node.label.thedef !== def) return;
+                    node.label.thedef = label;
+                    label.references.push(node);
+                    return true;
+                }
+                if (node instanceof AST_Scope) return true;
+            }));
+        }
+        return node;
+    },
+    _validate: function() {
+        if (!(this.label instanceof AST_Label)) throw new Error("label must be AST_Label");
+    },
+}, AST_StatementWithBody);
+
+var AST_IterationStatement = DEFNODE("IterationStatement", null, {
+    $documentation: "Internal class.  All loops inherit from it.",
+    _validate: function() {
+        if (this.TYPE == "IterationStatement") throw new Error("should not instantiate AST_IterationStatement");
+    },
+}, AST_StatementWithBody);
+
+var AST_DWLoop = DEFNODE("DWLoop", "condition", {
+    $documentation: "Base class for do/while statements",
+    $propdoc: {
+        condition: "[AST_Node] the loop condition.  Should not be instanceof AST_Statement"
+    },
+    _validate: function() {
+        if (this.TYPE == "DWLoop") throw new Error("should not instantiate AST_DWLoop");
+        must_be_expression(this, "condition");
+    },
+}, AST_IterationStatement);
+
+var AST_Do = DEFNODE("Do", null, {
+    $documentation: "A `do` statement",
+    walk: function(visitor) {
+        var node = this;
+        visitor.visit(node, function() {
+            node.body.walk(visitor);
+            node.condition.walk(visitor);
+        });
+    }
+}, AST_DWLoop);
+
+var AST_While = DEFNODE("While", null, {
+    $documentation: "A `while` statement",
+    walk: function(visitor) {
+        var node = this;
+        visitor.visit(node, function() {
+            node.condition.walk(visitor);
+            node.body.walk(visitor);
+        });
+    }
+}, AST_DWLoop);
+
+var AST_For = DEFNODE("For", "init condition step", {
+    $documentation: "A `for` statement",
+    $propdoc: {
+        init: "[AST_Node?] the `for` initialization code, or null if empty",
+        condition: "[AST_Node?] the `for` termination clause, or null if empty",
+        step: "[AST_Node?] the `for` update clause, or null if empty"
+    },
+    walk: function(visitor) {
+        var node = this;
+        visitor.visit(node, function() {
+            if (node.init) node.init.walk(visitor);
+            if (node.condition) node.condition.walk(visitor);
+            if (node.step) node.step.walk(visitor);
+            node.body.walk(visitor);
+        });
+    },
+    _validate: function() {
+        if (this.init != null) {
+            if (!(this.init instanceof AST_Node)) throw new Error("init must be AST_Node");
+            if (is_statement(this.init) && !(this.init instanceof AST_Definitions)) {
+                throw new Error("init cannot be AST_Statement");
+            }
+        }
+        if (this.condition != null) must_be_expression(this, "condition");
+        if (this.step != null) must_be_expression(this, "step");
+    },
+}, AST_IterationStatement);
+
+var AST_ForEnumeration = DEFNODE("ForEnumeration", "init object", {
+    $documentation: "Base class for enumeration loops, i.e. `for ... in`, `for ... of` & `for await ... of`",
+    $propdoc: {
+        init: "[AST_Node] the assignment target during iteration",
+        object: "[AST_Node] the object to iterate over"
+    },
+    walk: function(visitor) {
+        var node = this;
+        visitor.visit(node, function() {
+            node.init.walk(visitor);
+            node.object.walk(visitor);
+            node.body.walk(visitor);
+        });
+    },
+    _validate: function() {
+        if (this.TYPE == "ForEnumeration") throw new Error("should not instantiate AST_ForEnumeration");
+        if (this.init instanceof AST_Definitions) {
+            if (this.init.definitions.length != 1) throw new Error("init must have single declaration");
+        } else {
+            validate_destructured(this.init, function(node) {
+                if (!(node instanceof AST_PropAccess || node instanceof AST_SymbolRef)) {
+                    throw new Error("init must be assignable: " + node.TYPE);
+                }
+            });
+        }
+        must_be_expression(this, "object");
+    },
+}, AST_IterationStatement);
+
+var AST_ForIn = DEFNODE("ForIn", null, {
+    $documentation: "A `for ... in` statement",
+}, AST_ForEnumeration);
+
+var AST_ForOf = DEFNODE("ForOf", null, {
+    $documentation: "A `for ... of` statement",
+}, AST_ForEnumeration);
+
+var AST_ForAwaitOf = DEFNODE("ForAwaitOf", null, {
+    $documentation: "A `for await ... of` statement",
+}, AST_ForOf);
+
+var AST_With = DEFNODE("With", "expression", {
+    $documentation: "A `with` statement",
+    $propdoc: {
+        expression: "[AST_Node] the `with` expression"
+    },
+    walk: function(visitor) {
+        var node = this;
+        visitor.visit(node, function() {
+            node.expression.walk(visitor);
+            node.body.walk(visitor);
+        });
+    },
+    _validate: function() {
+        must_be_expression(this, "expression");
+    },
+}, AST_StatementWithBody);
+
+/* -----[ scope and functions ]----- */
+
+var AST_Scope = DEFNODE("Scope", "uses_eval uses_with", {
+    $documentation: "Base class for all statements introducing a lexical scope",
+    $propdoc: {
+        uses_eval: "[boolean/S] tells whether this scope contains a direct call to the global `eval`",
+        uses_with: "[boolean/S] tells whether this scope uses the `with` statement",
+    },
+    pinned: function() {
+        return this.uses_eval || this.uses_with;
+    },
+    resolve: return_this,
+    _validate: function() {
+        if (this.TYPE == "Scope") throw new Error("should not instantiate AST_Scope");
+    },
+}, AST_Block);
+
+var AST_Toplevel = DEFNODE("Toplevel", "globals", {
+    $documentation: "The toplevel scope",
+    $propdoc: {
+        globals: "[Dictionary/S] a map of name ---> SymbolDef for all undeclared names",
+    },
+    wrap: function(name) {
+        var body = this.body;
+        return parse([
+            "(function(exports){'$ORIG';})(typeof ",
+            name,
+            "=='undefined'?(",
+            name,
+            "={}):",
+            name,
+            ");"
+        ].join(""), {
+            filename: "wrap=" + JSON.stringify(name)
+        }).transform(new TreeTransformer(function(node) {
+            if (node instanceof AST_Directive && node.value == "$ORIG") {
+                return List.splice(body);
+            }
+        }));
+    },
+    enclose: function(args_values) {
+        if (typeof args_values != "string") args_values = "";
+        var index = args_values.indexOf(":");
+        if (index < 0) index = args_values.length;
+        var body = this.body;
+        return parse([
+            "(function(",
+            args_values.slice(0, index),
+            '){"$ORIG"})(',
+            args_values.slice(index + 1),
+            ")"
+        ].join(""), {
+            filename: "enclose=" + JSON.stringify(args_values)
+        }).transform(new TreeTransformer(function(node) {
+            if (node instanceof AST_Directive && node.value == "$ORIG") {
+                return List.splice(body);
+            }
+        }));
+    }
+}, AST_Scope);
+
+var AST_Lambda = DEFNODE("Lambda", "argnames length_read rest uses_arguments", {
+    $documentation: "Base class for functions",
+    $propdoc: {
+        argnames: "[(AST_DefaultValue|AST_Destructured|AST_SymbolFunarg)*] array of function arguments and/or destructured literals",
+        length_read: "[boolean/S] whether length property of this function is accessed",
+        rest: "[(AST_Destructured|AST_SymbolFunarg)?] rest parameter, or null if absent",
+        uses_arguments: "[boolean/S] whether this function accesses the arguments array",
+    },
+    each_argname: function(visit) {
+        var tw = new TreeWalker(function(node) {
+            if (node instanceof AST_DefaultValue) {
+                node.name.walk(tw);
+                return true;
+            }
+            if (node instanceof AST_DestructuredKeyVal) {
+                node.value.walk(tw);
+                return true;
+            }
+            if (node instanceof AST_SymbolFunarg) visit(node);
+        });
+        this.argnames.forEach(function(argname) {
+            argname.walk(tw);
+        });
+        if (this.rest) this.rest.walk(tw);
+    },
+    walk: function(visitor) {
+        var node = this;
+        visitor.visit(node, function() {
+            if (node.name) node.name.walk(visitor);
+            node.argnames.forEach(function(argname) {
+                argname.walk(visitor);
+            });
+            if (node.rest) node.rest.walk(visitor);
+            walk_body(node, visitor);
+        });
+    },
+    _validate: function() {
+        if (this.TYPE == "Lambda") throw new Error("should not instantiate AST_Lambda");
+        this.argnames.forEach(function(node) {
+            validate_destructured(node, function(node) {
+                if (!(node instanceof AST_SymbolFunarg)) throw new Error("argnames must be AST_SymbolFunarg[]");
+            }, true);
+        });
+        if (this.rest != null) validate_destructured(this.rest, function(node) {
+            if (!(node instanceof AST_SymbolFunarg)) throw new Error("rest must be AST_SymbolFunarg");
+        });
+    },
+}, AST_Scope);
+
+var AST_Accessor = DEFNODE("Accessor", null, {
+    $documentation: "A getter/setter function",
+    _validate: function() {
+        if (this.name != null) throw new Error("name must be null");
+    },
+}, AST_Lambda);
+
+var AST_LambdaExpression = DEFNODE("LambdaExpression", "inlined", {
+    $documentation: "Base class for function expressions",
+    $propdoc: {
+        inlined: "[boolean/S] whether this function has been inlined",
+    },
+    _validate: function() {
+        if (this.TYPE == "LambdaExpression") throw new Error("should not instantiate AST_LambdaExpression");
+    },
+}, AST_Lambda);
+
+function is_arrow(node) {
+    return node instanceof AST_Arrow || node instanceof AST_AsyncArrow;
+}
+
+function is_async(node) {
+    return node instanceof AST_AsyncArrow
+        || node instanceof AST_AsyncDefun
+        || node instanceof AST_AsyncFunction
+        || node instanceof AST_AsyncGeneratorDefun
+        || node instanceof AST_AsyncGeneratorFunction;
+}
+
+function is_generator(node) {
+    return node instanceof AST_AsyncGeneratorDefun
+        || node instanceof AST_AsyncGeneratorFunction
+        || node instanceof AST_GeneratorDefun
+        || node instanceof AST_GeneratorFunction;
+}
+
+function walk_lambda(node, tw) {
+    if (is_arrow(node) && node.value) {
+        node.value.walk(tw);
+    } else {
+        walk_body(node, tw);
+    }
+}
+
+var AST_Arrow = DEFNODE("Arrow", "value", {
+    $documentation: "An arrow function expression",
+    $propdoc: {
+        value: "[AST_Node?] simple return expression, or null if using function body.",
+    },
+    walk: function(visitor) {
+        var node = this;
+        visitor.visit(node, function() {
+            node.argnames.forEach(function(argname) {
+                argname.walk(visitor);
+            });
+            if (node.rest) node.rest.walk(visitor);
+            if (node.value) {
+                node.value.walk(visitor);
+            } else {
+                walk_body(node, visitor);
+            }
+        });
+    },
+    _validate: function() {
+        if (this.name != null) throw new Error("name must be null");
+        if (this.uses_arguments) throw new Error("uses_arguments must be false");
+        if (this.value != null) {
+            must_be_expression(this, "value");
+            if (this.body.length) throw new Error("body must be empty if value exists");
+        }
+    },
+}, AST_LambdaExpression);
+
+var AST_AsyncArrow = DEFNODE("AsyncArrow", "value", {
+    $documentation: "An asynchronous arrow function expression",
+    $propdoc: {
+        value: "[AST_Node?] simple return expression, or null if using function body.",
+    },
+    walk: function(visitor) {
+        var node = this;
+        visitor.visit(node, function() {
+            node.argnames.forEach(function(argname) {
+                argname.walk(visitor);
+            });
+            if (node.rest) node.rest.walk(visitor);
+            if (node.value) {
+                node.value.walk(visitor);
+            } else {
+                walk_body(node, visitor);
+            }
+        });
+    },
+    _validate: function() {
+        if (this.name != null) throw new Error("name must be null");
+        if (this.uses_arguments) throw new Error("uses_arguments must be false");
+        if (this.value != null) {
+            must_be_expression(this, "value");
+            if (this.body.length) throw new Error("body must be empty if value exists");
+        }
+    },
+}, AST_LambdaExpression);
+
+var AST_AsyncFunction = DEFNODE("AsyncFunction", "name", {
+    $documentation: "An asynchronous function expression",
+    $propdoc: {
+        name: "[AST_SymbolLambda?] the name of this function, or null if not specified",
+    },
+    _validate: function() {
+        if (this.name != null) {
+            if (!(this.name instanceof AST_SymbolLambda)) throw new Error("name must be AST_SymbolLambda");
+        }
+    },
+}, AST_LambdaExpression);
+
+var AST_AsyncGeneratorFunction = DEFNODE("AsyncGeneratorFunction", "name", {
+    $documentation: "An asynchronous generator function expression",
+    $propdoc: {
+        name: "[AST_SymbolLambda?] the name of this function, or null if not specified",
+    },
+    _validate: function() {
+        if (this.name != null) {
+            if (!(this.name instanceof AST_SymbolLambda)) throw new Error("name must be AST_SymbolLambda");
+        }
+    },
+}, AST_LambdaExpression);
+
+var AST_Function = DEFNODE("Function", "name", {
+    $documentation: "A function expression",
+    $propdoc: {
+        name: "[AST_SymbolLambda?] the name of this function, or null if not specified",
+    },
+    _validate: function() {
+        if (this.name != null) {
+            if (!(this.name instanceof AST_SymbolLambda)) throw new Error("name must be AST_SymbolLambda");
+        }
+    },
+}, AST_LambdaExpression);
+
+var AST_GeneratorFunction = DEFNODE("GeneratorFunction", "name", {
+    $documentation: "A generator function expression",
+    $propdoc: {
+        name: "[AST_SymbolLambda?] the name of this function, or null if not specified",
+    },
+    _validate: function() {
+        if (this.name != null) {
+            if (!(this.name instanceof AST_SymbolLambda)) throw new Error("name must be AST_SymbolLambda");
+        }
+    },
+}, AST_LambdaExpression);
+
+var AST_LambdaDefinition = DEFNODE("LambdaDefinition", "inlined name", {
+    $documentation: "Base class for function definitions",
+    $propdoc: {
+        inlined: "[boolean/S] whether this function has been inlined",
+        name: "[AST_SymbolDefun] the name of this function",
+    },
+    _validate: function() {
+        if (this.TYPE == "LambdaDefinition") throw new Error("should not instantiate AST_LambdaDefinition");
+        if (!(this.name instanceof AST_SymbolDefun)) throw new Error("name must be AST_SymbolDefun");
+    },
+}, AST_Lambda);
+
+var AST_AsyncDefun = DEFNODE("AsyncDefun", null, {
+    $documentation: "An asynchronous function definition",
+}, AST_LambdaDefinition);
+
+var AST_AsyncGeneratorDefun = DEFNODE("AsyncGeneratorDefun", null, {
+    $documentation: "An asynchronous generator function definition",
+}, AST_LambdaDefinition);
+
+var AST_Defun = DEFNODE("Defun", null, {
+    $documentation: "A function definition",
+}, AST_LambdaDefinition);
+
+var AST_GeneratorDefun = DEFNODE("GeneratorDefun", null, {
+    $documentation: "A generator function definition",
+}, AST_LambdaDefinition);
+
+/* -----[ classes ]----- */
+
+var AST_Class = DEFNODE("Class", "extends name properties", {
+    $documentation: "Base class for class literals",
+    $propdoc: {
+        extends: "[AST_Node?] the super class, or null if not specified",
+        properties: "[AST_ClassProperty*] array of class properties",
+    },
+    walk: function(visitor) {
+        var node = this;
+        visitor.visit(node, function() {
+            if (node.name) node.name.walk(visitor);
+            if (node.extends) node.extends.walk(visitor);
+            node.properties.forEach(function(prop) {
+                prop.walk(visitor);
+            });
+        });
+    },
+    _validate: function() {
+        if (this.TYPE == "Class") throw new Error("should not instantiate AST_Class");
+        if (this.extends != null) must_be_expression(this, "extends");
+        this.properties.forEach(function(node) {
+            if (!(node instanceof AST_ClassProperty)) throw new Error("properties must contain AST_ClassProperty");
+        });
+    },
+}, AST_BlockScope);
+
+var AST_DefClass = DEFNODE("DefClass", null, {
+    $documentation: "A class definition",
+    $propdoc: {
+        name: "[AST_SymbolDefClass] the name of this class",
+    },
+    _validate: function() {
+        if (!(this.name instanceof AST_SymbolDefClass)) throw new Error("name must be AST_SymbolDefClass");
+    },
+}, AST_Class);
+
+var AST_ClassExpression = DEFNODE("ClassExpression", null, {
+    $documentation: "A class expression",
+    $propdoc: {
+        name: "[AST_SymbolClass?] the name of this class, or null if not specified",
+    },
+    _validate: function() {
+        if (this.name != null) {
+            if (!(this.name instanceof AST_SymbolClass)) throw new Error("name must be AST_SymbolClass");
+        }
+    },
+}, AST_Class);
+
+var AST_ClassProperty = DEFNODE("ClassProperty", "key private static value", {
+    $documentation: "Base class for `class` properties",
+    $propdoc: {
+        key: "[string|AST_Node] property name (AST_Node for computed property)",
+        private: "[boolean] whether this is a private property",
+        static: "[boolean] whether this is a static property",
+        value: "[AST_Node?] property value (AST_Accessor for getters/setters, AST_LambdaExpression for methods, null if not specified for fields)",
+    },
+    walk: function(visitor) {
+        var node = this;
+        visitor.visit(node, function() {
+            if (node.key instanceof AST_Node) node.key.walk(visitor);
+            if (node.value) node.value.walk(visitor);
+        });
+    },
+    _validate: function() {
+        if (this.TYPE == "ClassProperty") throw new Error("should not instantiate AST_ClassProperty");
+        if (typeof this.key != "string") {
+            if (!(this.key instanceof AST_Node)) throw new Error("key must be string or AST_Node");
+            must_be_expression(this, "key");
+        }
+        if(this.value != null) {
+            if (!(this.value instanceof AST_Node)) throw new Error("value must be AST_Node");
+        }
+    },
+});
+
+var AST_ClassField = DEFNODE("ClassField", null, {
+    $documentation: "A `class` field",
+    _validate: function() {
+        if(this.value != null) must_be_expression(this, "value");
+    },
+}, AST_ClassProperty);
+
+var AST_ClassGetter = DEFNODE("ClassGetter", null, {
+    $documentation: "A `class` getter",
+    _validate: function() {
+        if (!(this.value instanceof AST_Accessor)) throw new Error("value must be AST_Accessor");
+    },
+}, AST_ClassProperty);
+
+var AST_ClassSetter = DEFNODE("ClassSetter", null, {
+    $documentation: "A `class` setter",
+    _validate: function() {
+        if (!(this.value instanceof AST_Accessor)) throw new Error("value must be AST_Accessor");
+    },
+}, AST_ClassProperty);
+
+var AST_ClassMethod = DEFNODE("ClassMethod", null, {
+    $documentation: "A `class` method",
+    _validate: function() {
+        if (!(this.value instanceof AST_LambdaExpression)) throw new Error("value must be AST_LambdaExpression");
+        if (is_arrow(this.value)) throw new Error("value cannot be AST_Arrow or AST_AsyncArrow");
+        if (this.value.name != null) throw new Error("name of class method's lambda must be null");
+    },
+}, AST_ClassProperty);
+
+/* -----[ JUMPS ]----- */
+
+var AST_Jump = DEFNODE("Jump", null, {
+    $documentation: "Base class for “jumps” (for now that's `return`, `throw`, `break` and `continue`)",
+    _validate: function() {
+        if (this.TYPE == "Jump") throw new Error("should not instantiate AST_Jump");
+    },
+}, AST_Statement);
+
+var AST_Exit = DEFNODE("Exit", "value", {
+    $documentation: "Base class for “exits” (`return` and `throw`)",
+    $propdoc: {
+        value: "[AST_Node?] the value returned or thrown by this statement; could be null for AST_Return"
+    },
+    walk: function(visitor) {
+        var node = this;
+        visitor.visit(node, function() {
+            if (node.value) node.value.walk(visitor);
+        });
+    },
+    _validate: function() {
+        if (this.TYPE == "Exit") throw new Error("should not instantiate AST_Exit");
+    },
+}, AST_Jump);
+
+var AST_Return = DEFNODE("Return", null, {
+    $documentation: "A `return` statement",
+    _validate: function() {
+        if (this.value != null) must_be_expression(this, "value");
+    },
+}, AST_Exit);
+
+var AST_Throw = DEFNODE("Throw", null, {
+    $documentation: "A `throw` statement",
+    _validate: function() {
+        must_be_expression(this, "value");
+    },
+}, AST_Exit);
+
+var AST_LoopControl = DEFNODE("LoopControl", "label", {
+    $documentation: "Base class for loop control statements (`break` and `continue`)",
+    $propdoc: {
+        label: "[AST_LabelRef?] the label, or null if none",
+    },
+    walk: function(visitor) {
+        var node = this;
+        visitor.visit(node, function() {
+            if (node.label) node.label.walk(visitor);
+        });
+    },
+    _validate: function() {
+        if (this.TYPE == "LoopControl") throw new Error("should not instantiate AST_LoopControl");
+        if (this.label != null) {
+            if (!(this.label instanceof AST_LabelRef)) throw new Error("label must be AST_LabelRef");
+        }
+    },
+}, AST_Jump);
+
+var AST_Break = DEFNODE("Break", null, {
+    $documentation: "A `break` statement"
+}, AST_LoopControl);
+
+var AST_Continue = DEFNODE("Continue", null, {
+    $documentation: "A `continue` statement"
+}, AST_LoopControl);
+
+/* -----[ IF ]----- */
+
+var AST_If = DEFNODE("If", "condition alternative", {
+    $documentation: "A `if` statement",
+    $propdoc: {
+        condition: "[AST_Node] the `if` condition",
+        alternative: "[AST_Statement?] the `else` part, or null if not present"
+    },
+    walk: function(visitor) {
+        var node = this;
+        visitor.visit(node, function() {
+            node.condition.walk(visitor);
+            node.body.walk(visitor);
+            if (node.alternative) node.alternative.walk(visitor);
+        });
+    },
+    _validate: function() {
+        must_be_expression(this, "condition");
+        if (this.alternative != null) {
+            if (!is_statement(this.alternative)) throw new Error("alternative must be AST_Statement");
+        }
+    },
+}, AST_StatementWithBody);
+
+/* -----[ SWITCH ]----- */
+
+var AST_Switch = DEFNODE("Switch", "expression", {
+    $documentation: "A `switch` statement",
+    $propdoc: {
+        expression: "[AST_Node] the `switch` “discriminant”"
+    },
+    walk: function(visitor) {
+        var node = this;
+        visitor.visit(node, function() {
+            node.expression.walk(visitor);
+            walk_body(node, visitor);
+        });
+    },
+    _validate: function() {
+        must_be_expression(this, "expression");
+        this.body.forEach(function(node) {
+            if (!(node instanceof AST_SwitchBranch)) throw new Error("body must be AST_SwitchBranch[]");
+        });
+    },
+}, AST_Block);
+
+var AST_SwitchBranch = DEFNODE("SwitchBranch", null, {
+    $documentation: "Base class for `switch` branches",
+    _validate: function() {
+        if (this.TYPE == "SwitchBranch") throw new Error("should not instantiate AST_SwitchBranch");
+    },
+}, AST_Block);
+
+var AST_Default = DEFNODE("Default", null, {
+    $documentation: "A `default` switch branch",
+}, AST_SwitchBranch);
+
+var AST_Case = DEFNODE("Case", "expression", {
+    $documentation: "A `case` switch branch",
+    $propdoc: {
+        expression: "[AST_Node] the `case` expression"
+    },
+    walk: function(visitor) {
+        var node = this;
+        visitor.visit(node, function() {
+            node.expression.walk(visitor);
+            walk_body(node, visitor);
+        });
+    },
+    _validate: function() {
+        must_be_expression(this, "expression");
+    },
+}, AST_SwitchBranch);
+
+/* -----[ EXCEPTIONS ]----- */
+
+var AST_Try = DEFNODE("Try", "bcatch bfinally", {
+    $documentation: "A `try` statement",
+    $propdoc: {
+        bcatch: "[AST_Catch?] the catch block, or null if not present",
+        bfinally: "[AST_Finally?] the finally block, or null if not present"
+    },
+    walk: function(visitor) {
+        var node = this;
+        visitor.visit(node, function() {
+            walk_body(node, visitor);
+            if (node.bcatch) node.bcatch.walk(visitor);
+            if (node.bfinally) node.bfinally.walk(visitor);
+        });
+    },
+    _validate: function() {
+        if (this.bcatch != null) {
+            if (!(this.bcatch instanceof AST_Catch)) throw new Error("bcatch must be AST_Catch");
+        }
+        if (this.bfinally != null) {
+            if (!(this.bfinally instanceof AST_Finally)) throw new Error("bfinally must be AST_Finally");
+        }
+    },
+}, AST_Block);
+
+var AST_Catch = DEFNODE("Catch", "argname", {
+    $documentation: "A `catch` node; only makes sense as part of a `try` statement",
+    $propdoc: {
+        argname: "[(AST_Destructured|AST_SymbolCatch)?] symbol for the exception, or null if not present",
+    },
+    walk: function(visitor) {
+        var node = this;
+        visitor.visit(node, function() {
+            if (node.argname) node.argname.walk(visitor);
+            walk_body(node, visitor);
+        });
+    },
+    _validate: function() {
+        if (this.argname != null) validate_destructured(this.argname, function(node) {
+            if (!(node instanceof AST_SymbolCatch)) throw new Error("argname must be AST_SymbolCatch");
+        });
+    },
+}, AST_Block);
+
+var AST_Finally = DEFNODE("Finally", null, {
+    $documentation: "A `finally` node; only makes sense as part of a `try` statement"
+}, AST_Block);
+
+/* -----[ VAR ]----- */
+
+var AST_Definitions = DEFNODE("Definitions", "definitions", {
+    $documentation: "Base class for `var` nodes (variable declarations/initializations)",
+    $propdoc: {
+        definitions: "[AST_VarDef*] array of variable definitions"
+    },
+    walk: function(visitor) {
+        var node = this;
+        visitor.visit(node, function() {
+            node.definitions.forEach(function(defn) {
+                defn.walk(visitor);
+            });
+        });
+    },
+    _validate: function() {
+        if (this.TYPE == "Definitions") throw new Error("should not instantiate AST_Definitions");
+        if (this.definitions.length < 1) throw new Error("must have at least one definition");
+    },
+}, AST_Statement);
+
+var AST_Const = DEFNODE("Const", null, {
+    $documentation: "A `const` statement",
+    _validate: function() {
+        this.definitions.forEach(function(node) {
+            if (!(node instanceof AST_VarDef)) throw new Error("definitions must be AST_VarDef[]");
+            validate_destructured(node.name, function(node) {
+                if (!(node instanceof AST_SymbolConst)) throw new Error("name must be AST_SymbolConst");
+            });
+        });
+    },
+}, AST_Definitions);
+
+var AST_Let = DEFNODE("Let", null, {
+    $documentation: "A `let` statement",
+    _validate: function() {
+        this.definitions.forEach(function(node) {
+            if (!(node instanceof AST_VarDef)) throw new Error("definitions must be AST_VarDef[]");
+            validate_destructured(node.name, function(node) {
+                if (!(node instanceof AST_SymbolLet)) throw new Error("name must be AST_SymbolLet");
+            });
+        });
+    },
+}, AST_Definitions);
+
+var AST_Var = DEFNODE("Var", null, {
+    $documentation: "A `var` statement",
+    _validate: function() {
+        this.definitions.forEach(function(node) {
+            if (!(node instanceof AST_VarDef)) throw new Error("definitions must be AST_VarDef[]");
+            validate_destructured(node.name, function(node) {
+                if (!(node instanceof AST_SymbolVar)) throw new Error("name must be AST_SymbolVar");
+            });
+        });
+    },
+}, AST_Definitions);
+
+var AST_VarDef = DEFNODE("VarDef", "name value", {
+    $documentation: "A variable declaration; only appears in a AST_Definitions node",
+    $propdoc: {
+        name: "[AST_Destructured|AST_SymbolVar] name of the variable",
+        value: "[AST_Node?] initializer, or null of there's no initializer",
+    },
+    walk: function(visitor) {
+        var node = this;
+        visitor.visit(node, function() {
+            node.name.walk(visitor);
+            if (node.value) node.value.walk(visitor);
+        });
+    },
+    _validate: function() {
+        if (this.value != null) must_be_expression(this, "value");
+    },
+});
+
+/* -----[ OTHER ]----- */
+
+var AST_ExportDeclaration = DEFNODE("ExportDeclaration", "body", {
+    $documentation: "An `export` statement",
+    $propdoc: {
+        body: "[AST_DefClass|AST_Definitions|AST_LambdaDefinition] the statement to export",
+    },
+    walk: function(visitor) {
+        var node = this;
+        visitor.visit(node, function() {
+            node.body.walk(visitor);
+        });
+    },
+    _validate: function() {
+        if (!(this.body instanceof AST_DefClass
+            || this.body instanceof AST_Definitions
+            || this.body instanceof AST_LambdaDefinition)) {
+            throw new Error("body must be AST_DefClass, AST_Definitions or AST_LambdaDefinition");
+        }
+    },
+}, AST_Statement);
+
+var AST_ExportDefault = DEFNODE("ExportDefault", "body", {
+    $documentation: "An `export default` statement",
+    $propdoc: {
+        body: "[AST_Node] the default export",
+    },
+    walk: function(visitor) {
+        var node = this;
+        visitor.visit(node, function() {
+            node.body.walk(visitor);
+        });
+    },
+    _validate: function() {
+        if (!(this.body instanceof AST_DefClass || this.body instanceof AST_LambdaDefinition)) {
+            must_be_expression(this, "body");
+        }
+    },
+}, AST_Statement);
+
+var AST_ExportForeign = DEFNODE("ExportForeign", "aliases keys path quote", {
+    $documentation: "An `export ... from '...'` statement",
+    $propdoc: {
+        aliases: "[string*] array of aliases to export",
+        keys: "[string*] array of keys to import",
+        path: "[string] the path to import module",
+        quote: "[string?] the original quote character",
+    },
+    _validate: function() {
+        if (this.aliases.length != this.keys.length) {
+            throw new Error("aliases:key length mismatch: " + this.aliases.length + " != " + this.keys.length);
+        }
+        this.aliases.forEach(function(name) {
+            if (typeof name != "string") throw new Error("aliases must contain string");
+        });
+        this.keys.forEach(function(name) {
+            if (typeof name != "string") throw new Error("keys must contain string");
+        });
+        if (typeof this.path != "string") throw new Error("path must be string");
+        if (this.quote != null) {
+            if (typeof this.quote != "string") throw new Error("quote must be string");
+            if (!/^["']$/.test(this.quote)) throw new Error("invalid quote: " + this.quote);
+        }
+    },
+}, AST_Statement);
+
+var AST_ExportReferences = DEFNODE("ExportReferences", "properties", {
+    $documentation: "An `export { ... }` statement",
+    $propdoc: {
+        properties: "[AST_SymbolExport*] array of aliases to export",
+    },
+    walk: function(visitor) {
+        var node = this;
+        visitor.visit(node, function() {
+            node.properties.forEach(function(prop) {
+                prop.walk(visitor);
+            });
+        });
+    },
+    _validate: function() {
+        this.properties.forEach(function(prop) {
+            if (!(prop instanceof AST_SymbolExport)) throw new Error("properties must contain AST_SymbolExport");
+        });
+    },
+}, AST_Statement);
+
+var AST_Import = DEFNODE("Import", "all default path properties quote", {
+    $documentation: "An `import` statement",
+    $propdoc: {
+        all: "[AST_SymbolImport?] the imported namespace, or null if not specified",
+        default: "[AST_SymbolImport?] the alias for default `export`, or null if not specified",
+        path: "[string] the path to import module",
+        properties: "[(AST_SymbolImport*)?] array of aliases, or null if not specified",
+        quote: "[string?] the original quote character",
+    },
+    walk: function(visitor) {
+        var node = this;
+        visitor.visit(node, function() {
+            if (node.all) node.all.walk(visitor);
+            if (node.default) node.default.walk(visitor);
+            if (node.properties) node.properties.forEach(function(prop) {
+                prop.walk(visitor);
+            });
+        });
+    },
+    _validate: function() {
+        if (this.all != null) {
+            if (!(this.all instanceof AST_SymbolImport)) throw new Error("all must be AST_SymbolImport");
+            if (this.properties != null) throw new Error("cannot import both * and {} in the same statement");
+        }
+        if (this.default != null) {
+            if (!(this.default instanceof AST_SymbolImport)) throw new Error("default must be AST_SymbolImport");
+            if (this.default.key !== "") throw new Error("invalid default key: " + this.default.key);
+        }
+        if (typeof this.path != "string") throw new Error("path must be string");
+        if (this.properties != null) this.properties.forEach(function(node) {
+            if (!(node instanceof AST_SymbolImport)) throw new Error("properties must contain AST_SymbolImport");
+        });
+        if (this.quote != null) {
+            if (typeof this.quote != "string") throw new Error("quote must be string");
+            if (!/^["']$/.test(this.quote)) throw new Error("invalid quote: " + this.quote);
+        }
+    },
+}, AST_Statement);
+
+var AST_DefaultValue = DEFNODE("DefaultValue", "name value", {
+    $documentation: "A default value declaration",
+    $propdoc: {
+        name: "[AST_Destructured|AST_SymbolDeclaration] name of the variable",
+        value: "[AST_Node] value to assign if variable is `undefined`",
+    },
+    walk: function(visitor) {
+        var node = this;
+        visitor.visit(node, function() {
+            node.name.walk(visitor);
+            node.value.walk(visitor);
+        });
+    },
+    _validate: function() {
+        must_be_expression(this, "value");
+    },
+});
+
+function must_be_expressions(node, prop, allow_spread, allow_hole) {
+    node[prop].forEach(function(node) {
+        validate_expression(node, prop, true, allow_spread, allow_hole);
+    });
+}
+
+var AST_Call = DEFNODE("Call", "args expression optional pure", {
+    $documentation: "A function call expression",
+    $propdoc: {
+        args: "[AST_Node*] array of arguments",
+        expression: "[AST_Node] expression to invoke as function",
+        optional: "[boolean] whether the expression is optional chaining",
+        pure: "[string/S] marker for side-effect-free call expression",
+    },
+    walk: function(visitor) {
+        var node = this;
+        visitor.visit(node, function() {
+            node.expression.walk(visitor);
+            node.args.forEach(function(arg) {
+                arg.walk(visitor);
+            });
+        });
+    },
+    _validate: function() {
+        must_be_expression(this, "expression");
+        must_be_expressions(this, "args", true);
+    },
+});
+
+var AST_New = DEFNODE("New", null, {
+    $documentation: "An object instantiation.  Derives from a function call since it has exactly the same properties",
+    _validate: function() {
+        if (this.optional) throw new Error("optional must be false");
+    },
+}, AST_Call);
+
+var AST_Sequence = DEFNODE("Sequence", "expressions", {
+    $documentation: "A sequence expression (comma-separated expressions)",
+    $propdoc: {
+        expressions: "[AST_Node*] array of expressions (at least two)"
+    },
+    walk: function(visitor) {
+        var node = this;
+        visitor.visit(node, function() {
+            node.expressions.forEach(function(expr) {
+                expr.walk(visitor);
+            });
+        });
+    },
+    _validate: function() {
+        if (this.expressions.length < 2) throw new Error("expressions must contain multiple elements");
+        must_be_expressions(this, "expressions");
+    },
+});
+
+var AST_PropAccess = DEFNODE("PropAccess", "expression optional property", {
+    $documentation: "Base class for property access expressions, i.e. `a.foo` or `a[\"foo\"]`",
+    $propdoc: {
+        expression: "[AST_Node] the “container” expression",
+        optional: "[boolean] whether the expression is optional chaining",
+        property: "[AST_Node|string] the property to access.  For AST_Dot this is always a plain string, while for AST_Sub it's an arbitrary AST_Node",
+    },
+    getProperty: function() {
+        var p = this.property;
+        if (p instanceof AST_Constant) {
+            return p.value;
+        }
+        if (p instanceof AST_UnaryPrefix
+            && p.operator == "void"
+            && p.expression instanceof AST_Constant) {
+            return;
+        }
+        return p;
+    },
+    _validate: function() {
+        if (this.TYPE == "PropAccess") throw new Error("should not instantiate AST_PropAccess");
+        must_be_expression(this, "expression");
+    },
+});
+
+var AST_Dot = DEFNODE("Dot", null, {
+    $documentation: "A dotted property access expression",
+    walk: function(visitor) {
+        var node = this;
+        visitor.visit(node, function() {
+            node.expression.walk(visitor);
+        });
+    },
+    _validate: function() {
+        if (typeof this.property != "string") throw new Error("property must be string");
+    },
+}, AST_PropAccess);
+
+var AST_Sub = DEFNODE("Sub", null, {
+    $documentation: "Index-style property access, i.e. `a[\"foo\"]`",
+    walk: function(visitor) {
+        var node = this;
+        visitor.visit(node, function() {
+            node.expression.walk(visitor);
+            node.property.walk(visitor);
+        });
+    },
+    _validate: function() {
+        must_be_expression(this, "property");
+    },
+}, AST_PropAccess);
+
+var AST_Spread = DEFNODE("Spread", "expression", {
+    $documentation: "Spread expression in array/object literals or function calls",
+    $propdoc: {
+        expression: "[AST_Node] expression to be expanded",
+    },
+    walk: function(visitor) {
+        var node = this;
+        visitor.visit(node, function() {
+            node.expression.walk(visitor);
+        });
+    },
+    _validate: function() {
+        must_be_expression(this, "expression");
+    },
+});
+
+var AST_Unary = DEFNODE("Unary", "operator expression", {
+    $documentation: "Base class for unary expressions",
+    $propdoc: {
+        operator: "[string] the operator",
+        expression: "[AST_Node] expression that this unary operator applies to"
+    },
+    walk: function(visitor) {
+        var node = this;
+        visitor.visit(node, function() {
+            node.expression.walk(visitor);
+        });
+    },
+    _validate: function() {
+        if (this.TYPE == "Unary") throw new Error("should not instantiate AST_Unary");
+        if (typeof this.operator != "string") throw new Error("operator must be string");
+        must_be_expression(this, "expression");
+    },
+});
+
+var AST_UnaryPrefix = DEFNODE("UnaryPrefix", null, {
+    $documentation: "Unary prefix expression, i.e. `typeof i` or `++i`"
+}, AST_Unary);
+
+var AST_UnaryPostfix = DEFNODE("UnaryPostfix", null, {
+    $documentation: "Unary postfix expression, i.e. `i++`"
+}, AST_Unary);
+
+var AST_Binary = DEFNODE("Binary", "operator left right", {
+    $documentation: "Binary expression, i.e. `a + b`",
+    $propdoc: {
+        left: "[AST_Node] left-hand side expression",
+        operator: "[string] the operator",
+        right: "[AST_Node] right-hand side expression"
+    },
+    walk: function(visitor) {
+        var node = this;
+        visitor.visit(node, function() {
+            node.left.walk(visitor);
+            node.right.walk(visitor);
+        });
+    },
+    _validate: function() {
+        if (!(this instanceof AST_Assign)) must_be_expression(this, "left");
+        if (typeof this.operator != "string") throw new Error("operator must be string");
+        must_be_expression(this, "right");
+    },
+});
+
+var AST_Conditional = DEFNODE("Conditional", "condition consequent alternative", {
+    $documentation: "Conditional expression using the ternary operator, i.e. `a ? b : c`",
+    $propdoc: {
+        condition: "[AST_Node]",
+        consequent: "[AST_Node]",
+        alternative: "[AST_Node]"
+    },
+    walk: function(visitor) {
+        var node = this;
+        visitor.visit(node, function() {
+            node.condition.walk(visitor);
+            node.consequent.walk(visitor);
+            node.alternative.walk(visitor);
+        });
+    },
+    _validate: function() {
+        must_be_expression(this, "condition");
+        must_be_expression(this, "consequent");
+        must_be_expression(this, "alternative");
+    },
+});
+
+var AST_Assign = DEFNODE("Assign", null, {
+    $documentation: "An assignment expression — `a = b + 5`",
+    _validate: function() {
+        if (this.operator.indexOf("=") < 0) throw new Error('operator must contain "="');
+        if (this.left instanceof AST_Destructured) {
+            if (this.operator != "=") throw new Error("invalid destructuring operator: " + this.operator);
+            validate_destructured(this.left, function(node) {
+                if (!(node instanceof AST_PropAccess || node instanceof AST_SymbolRef)) {
+                    throw new Error("left must be assignable: " + node.TYPE);
+                }
+            });
+        }
+    },
+}, AST_Binary);
+
+var AST_Await = DEFNODE("Await", "expression", {
+    $documentation: "An await expression",
+    $propdoc: {
+        expression: "[AST_Node] expression with Promise to resolve on",
+    },
+    walk: function(visitor) {
+        var node = this;
+        visitor.visit(node, function() {
+            node.expression.walk(visitor);
+        });
+    },
+    _validate: function() {
+        must_be_expression(this, "expression");
+    },
+});
+
+var AST_Yield = DEFNODE("Yield", "expression nested", {
+    $documentation: "A yield expression",
+    $propdoc: {
+        expression: "[AST_Node?] return value for iterator, or null if undefined",
+        nested: "[boolean] whether to iterate over expression as generator",
+    },
+    walk: function(visitor) {
+        var node = this;
+        visitor.visit(node, function() {
+            if (node.expression) node.expression.walk(visitor);
+        });
+    },
+    _validate: function() {
+        if (this.expression != null) {
+            must_be_expression(this, "expression");
+        } else if (this.nested) {
+            throw new Error("yield* must contain expression");
+        }
+    },
+});
+
+/* -----[ LITERALS ]----- */
+
+var AST_Array = DEFNODE("Array", "elements", {
+    $documentation: "An array literal",
+    $propdoc: {
+        elements: "[AST_Node*] array of elements"
+    },
+    walk: function(visitor) {
+        var node = this;
+        visitor.visit(node, function() {
+            node.elements.forEach(function(element) {
+                element.walk(visitor);
+            });
+        });
+    },
+    _validate: function() {
+        must_be_expressions(this, "elements", true, true);
+    },
+});
+
+var AST_Destructured = DEFNODE("Destructured", "rest", {
+    $documentation: "Base class for destructured literal",
+    $propdoc: {
+        rest: "[(AST_Destructured|AST_SymbolDeclaration|AST_SymbolRef)?] rest parameter, or null if absent",
+    },
+    _validate: function() {
+        if (this.TYPE == "Destructured") throw new Error("should not instantiate AST_Destructured");
+    },
+});
+
+function validate_destructured(node, check, allow_default) {
+    if (node instanceof AST_DefaultValue && allow_default) return validate_destructured(node.name, check);
+    if (node instanceof AST_Destructured) {
+        if (node.rest != null) validate_destructured(node.rest, check);
+        if (node instanceof AST_DestructuredArray) return node.elements.forEach(function(node) {
+            if (!(node instanceof AST_Hole)) validate_destructured(node, check, true);
+        });
+        if (node instanceof AST_DestructuredObject) return node.properties.forEach(function(prop) {
+            validate_destructured(prop.value, check, true);
+        });
+    }
+    check(node);
+}
+
+var AST_DestructuredArray = DEFNODE("DestructuredArray", "elements", {
+    $documentation: "A destructured array literal",
+    $propdoc: {
+        elements: "[(AST_DefaultValue|AST_Destructured|AST_SymbolDeclaration|AST_SymbolRef)*] array of elements",
+    },
+    walk: function(visitor) {
+        var node = this;
+        visitor.visit(node, function() {
+            node.elements.forEach(function(element) {
+                element.walk(visitor);
+            });
+            if (node.rest) node.rest.walk(visitor);
+        });
+    },
+}, AST_Destructured);
+
+var AST_DestructuredKeyVal = DEFNODE("DestructuredKeyVal", "key value", {
+    $documentation: "A key: value destructured property",
+    $propdoc: {
+        key: "[string|AST_Node] property name.  For computed property this is an AST_Node.",
+        value: "[AST_DefaultValue|AST_Destructured|AST_SymbolDeclaration|AST_SymbolRef] property value",
+    },
+    walk: function(visitor) {
+        var node = this;
+        visitor.visit(node, function() {
+            if (node.key instanceof AST_Node) node.key.walk(visitor);
+            node.value.walk(visitor);
+        });
+    },
+    _validate: function() {
+        if (typeof this.key != "string") {
+            if (!(this.key instanceof AST_Node)) throw new Error("key must be string or AST_Node");
+            must_be_expression(this, "key");
+        }
+        if (!(this.value instanceof AST_Node)) throw new Error("value must be AST_Node");
+    },
+});
+
+var AST_DestructuredObject = DEFNODE("DestructuredObject", "properties", {
+    $documentation: "A destructured object literal",
+    $propdoc: {
+        properties: "[AST_DestructuredKeyVal*] array of properties",
+    },
+    walk: function(visitor) {
+        var node = this;
+        visitor.visit(node, function() {
+            node.properties.forEach(function(prop) {
+                prop.walk(visitor);
+            });
+            if (node.rest) node.rest.walk(visitor);
+        });
+    },
+    _validate: function() {
+        this.properties.forEach(function(node) {
+            if (!(node instanceof AST_DestructuredKeyVal)) throw new Error("properties must be AST_DestructuredKeyVal[]");
+        });
+    },
+}, AST_Destructured);
+
+var AST_Object = DEFNODE("Object", "properties", {
+    $documentation: "An object literal",
+    $propdoc: {
+        properties: "[(AST_ObjectProperty|AST_Spread)*] array of properties"
+    },
+    walk: function(visitor) {
+        var node = this;
+        visitor.visit(node, function() {
+            node.properties.forEach(function(prop) {
+                prop.walk(visitor);
+            });
+        });
+    },
+    _validate: function() {
+        this.properties.forEach(function(node) {
+            if (!(node instanceof AST_ObjectProperty || node instanceof AST_Spread)) {
+                throw new Error("properties must contain AST_ObjectProperty and/or AST_Spread only");
+            }
+        });
+    },
+});
+
+var AST_ObjectProperty = DEFNODE("ObjectProperty", "key value", {
+    $documentation: "Base class for literal object properties",
+    $propdoc: {
+        key: "[string|AST_Node] property name.  For computed property this is an AST_Node.",
+        value: "[AST_Node] property value.  For getters and setters this is an AST_Accessor.",
+    },
+    walk: function(visitor) {
+        var node = this;
+        visitor.visit(node, function() {
+            if (node.key instanceof AST_Node) node.key.walk(visitor);
+            node.value.walk(visitor);
+        });
+    },
+    _validate: function() {
+        if (this.TYPE == "ObjectProperty") throw new Error("should not instantiate AST_ObjectProperty");
+        if (typeof this.key != "string") {
+            if (!(this.key instanceof AST_Node)) throw new Error("key must be string or AST_Node");
+            must_be_expression(this, "key");
+        }
+        if (!(this.value instanceof AST_Node)) throw new Error("value must be AST_Node");
+    },
+});
+
+var AST_ObjectKeyVal = DEFNODE("ObjectKeyVal", null, {
+    $documentation: "A key: value object property",
+    _validate: function() {
+        must_be_expression(this, "value");
+    },
+}, AST_ObjectProperty);
+
+var AST_ObjectMethod = DEFNODE("ObjectMethod", null, {
+    $documentation: "A key(){} object property",
+    _validate: function() {
+        if (!(this.value instanceof AST_LambdaExpression)) throw new Error("value must be AST_LambdaExpression");
+        if (is_arrow(this.value)) throw new Error("value cannot be AST_Arrow or AST_AsyncArrow");
+        if (this.value.name != null) throw new Error("name of object method's lambda must be null");
+    },
+}, AST_ObjectKeyVal);
+
+var AST_ObjectSetter = DEFNODE("ObjectSetter", null, {
+    $documentation: "An object setter property",
+    _validate: function() {
+        if (!(this.value instanceof AST_Accessor)) throw new Error("value must be AST_Accessor");
+    },
+}, AST_ObjectProperty);
+
+var AST_ObjectGetter = DEFNODE("ObjectGetter", null, {
+    $documentation: "An object getter property",
+    _validate: function() {
+        if (!(this.value instanceof AST_Accessor)) throw new Error("value must be AST_Accessor");
+    },
+}, AST_ObjectProperty);
+
+var AST_Symbol = DEFNODE("Symbol", "scope name thedef", {
+    $documentation: "Base class for all symbols",
+    $propdoc: {
+        name: "[string] name of this symbol",
+        scope: "[AST_Scope/S] the current scope (not necessarily the definition scope)",
+        thedef: "[SymbolDef/S] the definition of this symbol"
+    },
+    _validate: function() {
+        if (this.TYPE == "Symbol") throw new Error("should not instantiate AST_Symbol");
+        if (typeof this.name != "string") throw new Error("name must be string");
+    },
+});
+
+var AST_SymbolDeclaration = DEFNODE("SymbolDeclaration", "init", {
+    $documentation: "A declaration symbol (symbol in var, function name or argument, symbol in catch)",
+}, AST_Symbol);
+
+var AST_SymbolConst = DEFNODE("SymbolConst", null, {
+    $documentation: "Symbol defining a constant",
+}, AST_SymbolDeclaration);
+
+var AST_SymbolImport = DEFNODE("SymbolImport", "key", {
+    $documentation: "Symbol defined by an `import` statement",
+    $propdoc: {
+        key: "[string] the original `export` name",
+    },
+    _validate: function() {
+        if (typeof this.key != "string") throw new Error("key must be string");
+    },
+}, AST_SymbolConst);
+
+var AST_SymbolLet = DEFNODE("SymbolLet", null, {
+    $documentation: "Symbol defining a lexical-scoped variable",
+}, AST_SymbolDeclaration);
+
+var AST_SymbolVar = DEFNODE("SymbolVar", null, {
+    $documentation: "Symbol defining a variable",
+}, AST_SymbolDeclaration);
+
+var AST_SymbolFunarg = DEFNODE("SymbolFunarg", null, {
+    $documentation: "Symbol naming a function argument",
+}, AST_SymbolVar);
+
+var AST_SymbolDefun = DEFNODE("SymbolDefun", null, {
+    $documentation: "Symbol defining a function",
+}, AST_SymbolDeclaration);
+
+var AST_SymbolLambda = DEFNODE("SymbolLambda", null, {
+    $documentation: "Symbol naming a function expression",
+}, AST_SymbolDeclaration);
+
+var AST_SymbolDefClass = DEFNODE("SymbolDefClass", null, {
+    $documentation: "Symbol defining a class",
+}, AST_SymbolLet);
+
+var AST_SymbolClass = DEFNODE("SymbolClass", null, {
+    $documentation: "Symbol naming a class expression",
+}, AST_SymbolLet);
+
+var AST_SymbolCatch = DEFNODE("SymbolCatch", null, {
+    $documentation: "Symbol naming the exception in catch",
+}, AST_SymbolDeclaration);
+
+var AST_Label = DEFNODE("Label", "references", {
+    $documentation: "Symbol naming a label (declaration)",
+    $propdoc: {
+        references: "[AST_LoopControl*] a list of nodes referring to this label"
+    },
+    initialize: function() {
+        this.references = [];
+        this.thedef = this;
+    }
+}, AST_Symbol);
+
+var AST_SymbolRef = DEFNODE("SymbolRef", "fixed in_arg redef", {
+    $documentation: "Reference to some symbol (not definition/declaration)",
+}, AST_Symbol);
+
+var AST_SymbolExport = DEFNODE("SymbolExport", "alias", {
+    $documentation: "Reference in an `export` statement",
+    $propdoc: {
+        alias: "[string] the `export` alias",
+    },
+    _validate: function() {
+        if (typeof this.alias != "string") throw new Error("alias must be string");
+    },
+}, AST_SymbolRef);
+
+var AST_LabelRef = DEFNODE("LabelRef", null, {
+    $documentation: "Reference to a label symbol",
+}, AST_Symbol);
+
+var AST_ObjectIdentity = DEFNODE("ObjectIdentity", null, {
+    $documentation: "Base class for `super` & `this`",
+    _validate: function() {
+        if (this.TYPE == "ObjectIdentity") throw new Error("should not instantiate AST_ObjectIdentity");
+    },
+}, AST_Symbol);
+
+var AST_Super = DEFNODE("Super", null, {
+    $documentation: "The `super` symbol",
+    _validate: function() {
+        if (this.name !== "super") throw new Error('name must be "super"');
+    },
+}, AST_ObjectIdentity);
+
+var AST_This = DEFNODE("This", null, {
+    $documentation: "The `this` symbol",
+    _validate: function() {
+        if (this.TYPE == "This" && this.name !== "this") throw new Error('name must be "this"');
+    },
+}, AST_ObjectIdentity);
+
+var AST_NewTarget = DEFNODE("NewTarget", null, {
+    $documentation: "The `new.target` symbol",
+    initialize: function() {
+        this.name = "new.target";
+    },
+    _validate: function() {
+        if (this.name !== "new.target") throw new Error('name must be "new.target": ' + this.name);
+    },
+}, AST_This);
+
+var AST_Template = DEFNODE("Template", "expressions strings tag", {
+    $documentation: "A template literal, i.e. tag`str1${expr1}...strN${exprN}strN+1`",
+    $propdoc: {
+        expressions: "[AST_Node*] the placeholder expressions",
+        strings: "[string*] the raw text segments",
+        tag: "[AST_Node] tag function, or null if absent",
+    },
+    walk: function(visitor) {
+        var node = this;
+        visitor.visit(node, function() {
+            if (node.tag) node.tag.walk(visitor);
+            node.expressions.forEach(function(expr) {
+                expr.walk(visitor);
+            });
+        });
+    },
+    _validate: function() {
+        if (this.expressions.length + 1 != this.strings.length) {
+            throw new Error("malformed template with " + this.expressions.length + " placeholder(s) but " + this.strings.length + " text segment(s)");
+        }
+        must_be_expressions(this, "expressions");
+        this.strings.forEach(function(string) {
+            if (typeof string != "string") throw new Error("strings must contain string");
+        });
+        if (this.tag != null) must_be_expression(this, "tag");
+    },
+});
+
+var AST_Constant = DEFNODE("Constant", null, {
+    $documentation: "Base class for all constants",
+    _validate: function() {
+        if (this.TYPE == "Constant") throw new Error("should not instantiate AST_Constant");
+    },
+});
+
+var AST_String = DEFNODE("String", "quote value", {
+    $documentation: "A string literal",
+    $propdoc: {
+        quote: "[string?] the original quote character",
+        value: "[string] the contents of this string",
+    },
+    _validate: function() {
+        if (this.quote != null) {
+            if (typeof this.quote != "string") throw new Error("quote must be string");
+            if (!/^["']$/.test(this.quote)) throw new Error("invalid quote: " + this.quote);
+        }
+        if (typeof this.value != "string") throw new Error("value must be string");
+    },
+}, AST_Constant);
+
+var AST_Number = DEFNODE("Number", "value", {
+    $documentation: "A number literal",
+    $propdoc: {
+        value: "[number] the numeric value",
+    },
+    _validate: function() {
+        if (typeof this.value != "number") throw new Error("value must be number");
+        if (!isFinite(this.value)) throw new Error("value must be finite");
+        if (this.value < 0) throw new Error("value cannot be negative");
+    },
+}, AST_Constant);
+
+var AST_BigInt = DEFNODE("BigInt", "value", {
+    $documentation: "A BigInt literal",
+    $propdoc: {
+        value: "[string] the numeric representation",
+    },
+    _validate: function() {
+        if (typeof this.value != "string") throw new Error("value must be string");
+        if (this.value[0] == "-") throw new Error("value cannot be negative");
+    },
+}, AST_Constant);
+
+var AST_RegExp = DEFNODE("RegExp", "value", {
+    $documentation: "A regexp literal",
+    $propdoc: {
+        value: "[RegExp] the actual regexp"
+    },
+    _validate: function() {
+        if (!(this.value instanceof RegExp)) throw new Error("value must be RegExp");
+    },
+}, AST_Constant);
+
+var AST_Atom = DEFNODE("Atom", null, {
+    $documentation: "Base class for atoms",
+    _validate: function() {
+        if (this.TYPE == "Atom") throw new Error("should not instantiate AST_Atom");
+    },
+}, AST_Constant);
+
+var AST_Null = DEFNODE("Null", null, {
+    $documentation: "The `null` atom",
+    value: null
+}, AST_Atom);
+
+var AST_NaN = DEFNODE("NaN", null, {
+    $documentation: "The impossible value",
+    value: 0/0
+}, AST_Atom);
+
+var AST_Undefined = DEFNODE("Undefined", null, {
+    $documentation: "The `undefined` value",
+    value: function(){}()
+}, AST_Atom);
+
+var AST_Hole = DEFNODE("Hole", null, {
+    $documentation: "A hole in an array",
+    value: function(){}()
+}, AST_Atom);
+
+var AST_Infinity = DEFNODE("Infinity", null, {
+    $documentation: "The `Infinity` value",
+    value: 1/0
+}, AST_Atom);
+
+var AST_Boolean = DEFNODE("Boolean", null, {
+    $documentation: "Base class for booleans",
+    _validate: function() {
+        if (this.TYPE == "Boolean") throw new Error("should not instantiate AST_Boolean");
+    },
+}, AST_Atom);
+
+var AST_False = DEFNODE("False", null, {
+    $documentation: "The `false` atom",
+    value: false
+}, AST_Boolean);
+
+var AST_True = DEFNODE("True", null, {
+    $documentation: "The `true` atom",
+    value: true
+}, AST_Boolean);
+
+/* -----[ TreeWalker ]----- */
+
+function TreeWalker(callback) {
+    this.callback = callback;
+    this.directives = Object.create(null);
+    this.stack = [];
+}
+TreeWalker.prototype = {
+    visit: function(node, descend) {
+        this.push(node);
+        var done = this.callback(node, descend || noop);
+        if (!done && descend) descend();
+        this.pop();
+    },
+    parent: function(n) {
+        return this.stack[this.stack.length - 2 - (n || 0)];
+    },
+    push: function(node) {
+        if (node instanceof AST_Lambda) {
+            this.directives = Object.create(this.directives);
+        } else if (node instanceof AST_Directive && !this.directives[node.value]) {
+            this.directives[node.value] = node;
+        }
+        this.stack.push(node);
+    },
+    pop: function() {
+        var node = this.stack.pop();
+        if (node instanceof AST_Lambda) {
+            this.directives = Object.getPrototypeOf(this.directives);
+        }
+    },
+    self: function() {
+        return this.stack[this.stack.length - 1];
+    },
+    find_parent: function(type) {
+        var stack = this.stack;
+        for (var i = stack.length; --i >= 0;) {
+            var x = stack[i];
+            if (x instanceof type) return x;
+        }
+    },
+    has_directive: function(type) {
+        var dir = this.directives[type];
+        if (dir) return dir;
+        var node = this.stack[this.stack.length - 1];
+        if (node instanceof AST_Scope) {
+            for (var i = 0; i < node.body.length; ++i) {
+                var st = node.body[i];
+                if (!(st instanceof AST_Directive)) break;
+                if (st.value == type) return st;
+            }
+        }
+    },
+    loopcontrol_target: function(node) {
+        var stack = this.stack;
+        if (node.label) for (var i = stack.length; --i >= 0;) {
+            var x = stack[i];
+            if (x instanceof AST_LabeledStatement && x.label.name == node.label.name)
+                return x.body;
+        } else for (var i = stack.length; --i >= 0;) {
+            var x = stack[i];
+            if (x instanceof AST_IterationStatement
+                || node instanceof AST_Break && x instanceof AST_Switch)
+                return x;
+        }
+    },
+    in_boolean_context: function() {
+        var self = this.self();
+        for (var i = 0, p; p = this.parent(i); i++) {
+            if (p instanceof AST_Conditional && p.condition === self
+                || p instanceof AST_DWLoop && p.condition === self
+                || p instanceof AST_For && p.condition === self
+                || p instanceof AST_If && p.condition === self
+                || p instanceof AST_Return && p.in_bool
+                || p instanceof AST_Sequence && p.tail_node() !== self
+                || p instanceof AST_SimpleStatement
+                || p instanceof AST_UnaryPrefix && p.operator == "!" && p.expression === self) {
+                return true;
+            }
+            if (p instanceof AST_Binary && (p.operator == "&&" || p.operator == "||")
+                || p instanceof AST_Conditional
+                || p.tail_node() === self) {
+                self = p;
+            } else if (p instanceof AST_Return) {
+                for (var call, fn = p; call = this.parent(++i); fn = call) {
+                    if (call.TYPE == "Call") {
+                        if (!(fn instanceof AST_Lambda) || fn.name) return false;
+                    } else if (fn instanceof AST_Lambda) {
+                        return false;
+                    }
+                }
+            } else {
+                return false;
+            }
+        }
+    }
+};