Updated the files.

my-app/node_modules/terser/lib/compress/common.js

@@ -0,0 +1,348 @@
+/***********************************************************************
+
+  A JavaScript tokenizer / parser / beautifier / compressor.
+  https://github.com/mishoo/UglifyJS2
+
+  -------------------------------- (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.
+
+ ***********************************************************************/
+
+import {
+    AST_Array,
+    AST_Arrow,
+    AST_BlockStatement,
+    AST_Call,
+    AST_Chain,
+    AST_Class,
+    AST_Const,
+    AST_Constant,
+    AST_DefClass,
+    AST_Defun,
+    AST_EmptyStatement,
+    AST_Export,
+    AST_False,
+    AST_Function,
+    AST_Import,
+    AST_Infinity,
+    AST_LabeledStatement,
+    AST_Lambda,
+    AST_Let,
+    AST_LoopControl,
+    AST_NaN,
+    AST_Node,
+    AST_Null,
+    AST_Number,
+    AST_Object,
+    AST_ObjectKeyVal,
+    AST_PropAccess,
+    AST_RegExp,
+    AST_Scope,
+    AST_Sequence,
+    AST_SimpleStatement,
+    AST_Statement,
+    AST_String,
+    AST_SymbolRef,
+    AST_True,
+    AST_UnaryPrefix,
+    AST_Undefined,
+
+    TreeWalker,
+    walk,
+    walk_abort,
+    walk_parent,
+} from "../ast.js";
+import { make_node, regexp_source_fix, string_template, makePredicate } from "../utils/index.js";
+import { first_in_statement } from "../utils/first_in_statement.js";
+import { has_flag, TOP } from "./compressor-flags.js";
+
+export function merge_sequence(array, node) {
+    if (node instanceof AST_Sequence) {
+        array.push(...node.expressions);
+    } else {
+        array.push(node);
+    }
+    return array;
+}
+
+export function make_sequence(orig, expressions) {
+    if (expressions.length == 1) return expressions[0];
+    if (expressions.length == 0) throw new Error("trying to create a sequence with length zero!");
+    return make_node(AST_Sequence, orig, {
+        expressions: expressions.reduce(merge_sequence, [])
+    });
+}
+
+export function make_node_from_constant(val, orig) {
+    switch (typeof val) {
+      case "string":
+        return make_node(AST_String, orig, {
+            value: val
+        });
+      case "number":
+        if (isNaN(val)) return make_node(AST_NaN, orig);
+        if (isFinite(val)) {
+            return 1 / val < 0 ? make_node(AST_UnaryPrefix, orig, {
+                operator: "-",
+                expression: make_node(AST_Number, orig, { value: -val })
+            }) : make_node(AST_Number, orig, { value: val });
+        }
+        return val < 0 ? make_node(AST_UnaryPrefix, orig, {
+            operator: "-",
+            expression: make_node(AST_Infinity, orig)
+        }) : make_node(AST_Infinity, orig);
+      case "boolean":
+        return make_node(val ? AST_True : AST_False, orig);
+      case "undefined":
+        return make_node(AST_Undefined, orig);
+      default:
+        if (val === null) {
+            return make_node(AST_Null, orig, { value: null });
+        }
+        if (val instanceof RegExp) {
+            return make_node(AST_RegExp, orig, {
+                value: {
+                    source: regexp_source_fix(val.source),
+                    flags: val.flags
+                }
+            });
+        }
+        throw new Error(string_template("Can't handle constant of type: {type}", {
+            type: typeof val
+        }));
+    }
+}
+
+export function best_of_expression(ast1, ast2) {
+    return ast1.size() > ast2.size() ? ast2 : ast1;
+}
+
+export function best_of_statement(ast1, ast2) {
+    return best_of_expression(
+        make_node(AST_SimpleStatement, ast1, {
+            body: ast1
+        }),
+        make_node(AST_SimpleStatement, ast2, {
+            body: ast2
+        })
+    ).body;
+}
+
+/** Find which node is smaller, and return that */
+export function best_of(compressor, ast1, ast2) {
+    if (first_in_statement(compressor)) {
+        return best_of_statement(ast1, ast2);
+    } else {
+        return best_of_expression(ast1, ast2);
+    }
+}
+
+/** Simplify an object property's key, if possible */
+export function get_simple_key(key) {
+    if (key instanceof AST_Constant) {
+        return key.getValue();
+    }
+    if (key instanceof AST_UnaryPrefix
+        && key.operator == "void"
+        && key.expression instanceof AST_Constant) {
+        return;
+    }
+    return key;
+}
+
+export function read_property(obj, key) {
+    key = get_simple_key(key);
+    if (key instanceof AST_Node) return;
+
+    var value;
+    if (obj instanceof AST_Array) {
+        var elements = obj.elements;
+        if (key == "length") return make_node_from_constant(elements.length, obj);
+        if (typeof key == "number" && key in elements) value = elements[key];
+    } else if (obj instanceof AST_Object) {
+        key = "" + key;
+        var props = obj.properties;
+        for (var i = props.length; --i >= 0;) {
+            var prop = props[i];
+            if (!(prop instanceof AST_ObjectKeyVal)) return;
+            if (!value && props[i].key === key) value = props[i].value;
+        }
+    }
+
+    return value instanceof AST_SymbolRef && value.fixed_value() || value;
+}
+
+export function has_break_or_continue(loop, parent) {
+    var found = false;
+    var tw = new TreeWalker(function(node) {
+        if (found || node instanceof AST_Scope) return true;
+        if (node instanceof AST_LoopControl && tw.loopcontrol_target(node) === loop) {
+            return found = true;
+        }
+    });
+    if (parent instanceof AST_LabeledStatement) tw.push(parent);
+    tw.push(loop);
+    loop.body.walk(tw);
+    return found;
+}
+
+// we shouldn't compress (1,func)(something) to
+// func(something) because that changes the meaning of
+// the func (becomes lexical instead of global).
+export function maintain_this_binding(parent, orig, val) {
+    if (
+        parent instanceof AST_UnaryPrefix && parent.operator == "delete"
+        || parent instanceof AST_Call && parent.expression === orig
+            && (
+                val instanceof AST_Chain
+                || val instanceof AST_PropAccess
+                || val instanceof AST_SymbolRef && val.name == "eval"
+            )
+    ) {
+        const zero = make_node(AST_Number, orig, { value: 0 });
+        return make_sequence(orig, [ zero, val ]);
+    } else {
+        return val;
+    }
+}
+
+export function is_func_expr(node) {
+    return node instanceof AST_Arrow || node instanceof AST_Function;
+}
+
+/**
+ * Used to determine whether the node can benefit from negation.
+ * Not the case with arrow functions (you need an extra set of parens). */
+export function is_iife_call(node) {
+    if (node.TYPE != "Call") return false;
+    return node.expression instanceof AST_Function || is_iife_call(node.expression);
+}
+
+export function is_empty(thing) {
+    if (thing === null) return true;
+    if (thing instanceof AST_EmptyStatement) return true;
+    if (thing instanceof AST_BlockStatement) return thing.body.length == 0;
+    return false;
+}
+
+export const identifier_atom = makePredicate("Infinity NaN undefined");
+export function is_identifier_atom(node) {
+    return node instanceof AST_Infinity
+        || node instanceof AST_NaN
+        || node instanceof AST_Undefined;
+}
+
+/** Check if this is a SymbolRef node which has one def of a certain AST type */
+export function is_ref_of(ref, type) {
+    if (!(ref instanceof AST_SymbolRef)) return false;
+    var orig = ref.definition().orig;
+    for (var i = orig.length; --i >= 0;) {
+        if (orig[i] instanceof type) return true;
+    }
+}
+
+/**Can we turn { block contents... } into just the block contents ?
+ * Not if one of these is inside.
+ **/
+export function can_be_evicted_from_block(node) {
+    return !(
+        node instanceof AST_DefClass ||
+        node instanceof AST_Defun ||
+        node instanceof AST_Let ||
+        node instanceof AST_Const ||
+        node instanceof AST_Export ||
+        node instanceof AST_Import
+    );
+}
+
+export function as_statement_array(thing) {
+    if (thing === null) return [];
+    if (thing instanceof AST_BlockStatement) return thing.body;
+    if (thing instanceof AST_EmptyStatement) return [];
+    if (thing instanceof AST_Statement) return [ thing ];
+    throw new Error("Can't convert thing to statement array");
+}
+
+export function is_reachable(scope_node, defs) {
+    const find_ref = node => {
+        if (node instanceof AST_SymbolRef && defs.includes(node.definition())) {
+            return walk_abort;
+        }
+    };
+
+    return walk_parent(scope_node, (node, info) => {
+        if (node instanceof AST_Scope && node !== scope_node) {
+            var parent = info.parent();
+
+            if (
+                parent instanceof AST_Call
+                && parent.expression === node
+                // Async/Generators aren't guaranteed to sync evaluate all of
+                // their body steps, so it's possible they close over the variable.
+                && !(node.async || node.is_generator)
+            ) {
+                return;
+            }
+
+            if (walk(node, find_ref)) return walk_abort;
+
+            return true;
+        }
+    });
+}
+
+/** Check if a ref refers to the name of a function/class it's defined within */
+export function is_recursive_ref(compressor, def) {
+    var node;
+    for (var i = 0; node = compressor.parent(i); i++) {
+        if (node instanceof AST_Lambda || node instanceof AST_Class) {
+            var name = node.name;
+            if (name && name.definition() === def) {
+                return true;
+            }
+        }
+    }
+    return false;
+}
+
+// TODO this only works with AST_Defun, shouldn't it work for other ways of defining functions?
+export function retain_top_func(fn, compressor) {
+    return compressor.top_retain
+        && fn instanceof AST_Defun
+        && has_flag(fn, TOP)
+        && fn.name
+        && compressor.top_retain(fn.name.definition());
+}

my-app/node_modules/terser/lib/compress/compressor-flags.js

@@ -0,0 +1,63 @@
+/***********************************************************************
+
+  A JavaScript tokenizer / parser / beautifier / compressor.
+  https://github.com/mishoo/UglifyJS2
+
+  -------------------------------- (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.
+
+ ***********************************************************************/
+
+// bitfield flags to be stored in node.flags.
+// These are set and unset during compression, and store information in the node without requiring multiple fields.
+export const UNUSED = 0b00000001;
+export const TRUTHY = 0b00000010;
+export const FALSY = 0b00000100;
+export const UNDEFINED = 0b00001000;
+export const INLINED = 0b00010000;
+
+// Nodes to which values are ever written. Used when keep_assign is part of the unused option string.
+export const WRITE_ONLY = 0b00100000;
+
+// information specific to a single compression pass
+export const SQUEEZED = 0b0000000100000000;
+export const OPTIMIZED = 0b0000001000000000;
+export const TOP = 0b0000010000000000;
+export const CLEAR_BETWEEN_PASSES = SQUEEZED | OPTIMIZED | TOP;
+
+export const has_flag = (node, flag) => node.flags & flag;
+export const set_flag = (node, flag) => { node.flags |= flag; };
+export const clear_flag = (node, flag) => { node.flags &= ~flag; };

my-app/node_modules/terser/lib/compress/drop-side-effect-free.js

@@ -0,0 +1,375 @@
+/***********************************************************************
+
+  A JavaScript tokenizer / parser / beautifier / compressor.
+  https://github.com/mishoo/UglifyJS2
+
+  -------------------------------- (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.
+
+ ***********************************************************************/
+
+import {
+    AST_Accessor,
+    AST_Array,
+    AST_Arrow,
+    AST_Assign,
+    AST_Binary,
+    AST_Call,
+    AST_Chain,
+    AST_Class,
+    AST_ClassStaticBlock,
+    AST_ClassProperty,
+    AST_ConciseMethod,
+    AST_Conditional,
+    AST_Constant,
+    AST_DefClass,
+    AST_Dot,
+    AST_Expansion,
+    AST_Function,
+    AST_Node,
+    AST_Number,
+    AST_Object,
+    AST_ObjectGetter,
+    AST_ObjectKeyVal,
+    AST_ObjectProperty,
+    AST_ObjectSetter,
+    AST_PropAccess,
+    AST_Scope,
+    AST_Sequence,
+    AST_SimpleStatement,
+    AST_Sub,
+    AST_SymbolRef,
+    AST_TemplateSegment,
+    AST_TemplateString,
+    AST_This,
+    AST_Unary,
+} from "../ast.js";
+import { make_node, return_null, return_this } from "../utils/index.js";
+import { first_in_statement } from "../utils/first_in_statement.js";
+
+import { pure_prop_access_globals } from "./native-objects.js";
+import { lazy_op, unary_side_effects, is_nullish_shortcircuited } from "./inference.js";
+import { WRITE_ONLY, set_flag, clear_flag } from "./compressor-flags.js";
+import { make_sequence, is_func_expr, is_iife_call } from "./common.js";
+
+// AST_Node#drop_side_effect_free() gets called when we don't care about the value,
+// only about side effects. We'll be defining this method for each node type in this module
+//
+// Examples:
+// foo++ -> foo++
+// 1 + func() -> func()
+// 10 -> (nothing)
+// knownPureFunc(foo++) -> foo++
+
+function def_drop_side_effect_free(node, func) {
+    node.DEFMETHOD("drop_side_effect_free", func);
+}
+
+// Drop side-effect-free elements from an array of expressions.
+// Returns an array of expressions with side-effects or null
+// if all elements were dropped. Note: original array may be
+// returned if nothing changed.
+function trim(nodes, compressor, first_in_statement) {
+    var len = nodes.length;
+    if (!len)  return null;
+
+    var ret = [], changed = false;
+    for (var i = 0; i < len; i++) {
+        var node = nodes[i].drop_side_effect_free(compressor, first_in_statement);
+        changed |= node !== nodes[i];
+        if (node) {
+            ret.push(node);
+            first_in_statement = false;
+        }
+    }
+    return changed ? ret.length ? ret : null : nodes;
+}
+
+def_drop_side_effect_free(AST_Node, return_this);
+def_drop_side_effect_free(AST_Constant, return_null);
+def_drop_side_effect_free(AST_This, return_null);
+
+def_drop_side_effect_free(AST_Call, function (compressor, first_in_statement) {
+    if (is_nullish_shortcircuited(this, compressor)) {
+        return this.expression.drop_side_effect_free(compressor, first_in_statement);
+    }
+
+    if (!this.is_callee_pure(compressor)) {
+        if (this.expression.is_call_pure(compressor)) {
+            var exprs = this.args.slice();
+            exprs.unshift(this.expression.expression);
+            exprs = trim(exprs, compressor, first_in_statement);
+            return exprs && make_sequence(this, exprs);
+        }
+        if (is_func_expr(this.expression)
+            && (!this.expression.name || !this.expression.name.definition().references.length)) {
+            var node = this.clone();
+            node.expression.process_expression(false, compressor);
+            return node;
+        }
+        return this;
+    }
+
+    var args = trim(this.args, compressor, first_in_statement);
+    return args && make_sequence(this, args);
+});
+
+def_drop_side_effect_free(AST_Accessor, return_null);
+
+def_drop_side_effect_free(AST_Function, return_null);
+
+def_drop_side_effect_free(AST_Arrow, return_null);
+
+def_drop_side_effect_free(AST_Class, function (compressor) {
+    const with_effects = [];
+    const trimmed_extends = this.extends && this.extends.drop_side_effect_free(compressor);
+    if (trimmed_extends)
+        with_effects.push(trimmed_extends);
+
+    for (const prop of this.properties) {
+        if (prop instanceof AST_ClassStaticBlock) {
+            if (prop.has_side_effects(compressor)) {
+                return this; // Be cautious about these
+            }
+        } else {
+            const trimmed_prop = prop.drop_side_effect_free(compressor);
+            if (trimmed_prop) {
+                if (trimmed_prop.contains_this()) return this;
+
+                with_effects.push(trimmed_prop);
+            }
+        }
+    }
+
+    if (!with_effects.length)
+        return null;
+
+    const exprs = make_sequence(this, with_effects);
+    if (this instanceof AST_DefClass) {
+        // We want a statement
+        return make_node(AST_SimpleStatement, this, { body: exprs });
+    } else {
+        return exprs;
+    }
+});
+
+def_drop_side_effect_free(AST_ClassProperty, function (compressor) {
+    const key = this.computed_key() && this.key.drop_side_effect_free(compressor);
+
+    const value = this.static && this.value
+        && this.value.drop_side_effect_free(compressor);
+
+    if (key && value)
+        return make_sequence(this, [key, value]);
+    return key || value || null;
+});
+
+def_drop_side_effect_free(AST_Binary, function (compressor, first_in_statement) {
+    var right = this.right.drop_side_effect_free(compressor);
+    if (!right)
+        return this.left.drop_side_effect_free(compressor, first_in_statement);
+    if (lazy_op.has(this.operator)) {
+        if (right === this.right)
+            return this;
+        var node = this.clone();
+        node.right = right;
+        return node;
+    } else {
+        var left = this.left.drop_side_effect_free(compressor, first_in_statement);
+        if (!left)
+            return this.right.drop_side_effect_free(compressor, first_in_statement);
+        return make_sequence(this, [left, right]);
+    }
+});
+
+def_drop_side_effect_free(AST_Assign, function (compressor) {
+    if (this.logical)
+        return this;
+
+    var left = this.left;
+    if (left.has_side_effects(compressor)
+        || compressor.has_directive("use strict")
+        && left instanceof AST_PropAccess
+        && left.expression.is_constant()) {
+        return this;
+    }
+    set_flag(this, WRITE_ONLY);
+    while (left instanceof AST_PropAccess) {
+        left = left.expression;
+    }
+    if (left.is_constant_expression(compressor.find_parent(AST_Scope))) {
+        return this.right.drop_side_effect_free(compressor);
+    }
+    return this;
+});
+
+def_drop_side_effect_free(AST_Conditional, function (compressor) {
+    var consequent = this.consequent.drop_side_effect_free(compressor);
+    var alternative = this.alternative.drop_side_effect_free(compressor);
+    if (consequent === this.consequent && alternative === this.alternative)
+        return this;
+    if (!consequent)
+        return alternative ? make_node(AST_Binary, this, {
+            operator: "||",
+            left: this.condition,
+            right: alternative
+        }) : this.condition.drop_side_effect_free(compressor);
+    if (!alternative)
+        return make_node(AST_Binary, this, {
+            operator: "&&",
+            left: this.condition,
+            right: consequent
+        });
+    var node = this.clone();
+    node.consequent = consequent;
+    node.alternative = alternative;
+    return node;
+});
+
+def_drop_side_effect_free(AST_Unary, function (compressor, first_in_statement) {
+    if (unary_side_effects.has(this.operator)) {
+        if (!this.expression.has_side_effects(compressor)) {
+            set_flag(this, WRITE_ONLY);
+        } else {
+            clear_flag(this, WRITE_ONLY);
+        }
+        return this;
+    }
+    if (this.operator == "typeof" && this.expression instanceof AST_SymbolRef)
+        return null;
+    var expression = this.expression.drop_side_effect_free(compressor, first_in_statement);
+    if (first_in_statement && expression && is_iife_call(expression)) {
+        if (expression === this.expression && this.operator == "!")
+            return this;
+        return expression.negate(compressor, first_in_statement);
+    }
+    return expression;
+});
+
+def_drop_side_effect_free(AST_SymbolRef, function (compressor) {
+    const safe_access = this.is_declared(compressor)
+        || pure_prop_access_globals.has(this.name);
+    return safe_access ? null : this;
+});
+
+def_drop_side_effect_free(AST_Object, function (compressor, first_in_statement) {
+    var values = trim(this.properties, compressor, first_in_statement);
+    return values && make_sequence(this, values);
+});
+
+def_drop_side_effect_free(AST_ObjectProperty, function (compressor, first_in_statement) {
+    const computed_key = this instanceof AST_ObjectKeyVal && this.key instanceof AST_Node;
+    const key = computed_key && this.key.drop_side_effect_free(compressor, first_in_statement);
+    const value = this.value && this.value.drop_side_effect_free(compressor, first_in_statement);
+    if (key && value) {
+        return make_sequence(this, [key, value]);
+    }
+    return key || value;
+});
+
+def_drop_side_effect_free(AST_ConciseMethod, function () {
+    return this.computed_key() ? this.key : null;
+});
+
+def_drop_side_effect_free(AST_ObjectGetter, function () {
+    return this.computed_key() ? this.key : null;
+});
+
+def_drop_side_effect_free(AST_ObjectSetter, function () {
+    return this.computed_key() ? this.key : null;
+});
+
+def_drop_side_effect_free(AST_Array, function (compressor, first_in_statement) {
+    var values = trim(this.elements, compressor, first_in_statement);
+    return values && make_sequence(this, values);
+});
+
+def_drop_side_effect_free(AST_Dot, function (compressor, first_in_statement) {
+    if (is_nullish_shortcircuited(this, compressor)) {
+        return this.expression.drop_side_effect_free(compressor, first_in_statement);
+    }
+    if (!this.optional && this.expression.may_throw_on_access(compressor)) {
+        return this;
+    }
+
+    return this.expression.drop_side_effect_free(compressor, first_in_statement);
+});
+
+def_drop_side_effect_free(AST_Sub, function (compressor, first_in_statement) {
+    if (is_nullish_shortcircuited(this, compressor)) {
+        return this.expression.drop_side_effect_free(compressor, first_in_statement);
+    }
+    if (!this.optional && this.expression.may_throw_on_access(compressor)) {
+        return this;
+    }
+
+    var property = this.property.drop_side_effect_free(compressor);
+    if (property && this.optional) return this;
+
+    var expression = this.expression.drop_side_effect_free(compressor, first_in_statement);
+
+    if (expression && property) return make_sequence(this, [expression, property]);
+    return expression || property;
+});
+
+def_drop_side_effect_free(AST_Chain, function (compressor, first_in_statement) {
+    return this.expression.drop_side_effect_free(compressor, first_in_statement);
+});
+
+def_drop_side_effect_free(AST_Sequence, function (compressor) {
+    var last = this.tail_node();
+    var expr = last.drop_side_effect_free(compressor);
+    if (expr === last)
+        return this;
+    var expressions = this.expressions.slice(0, -1);
+    if (expr)
+        expressions.push(expr);
+    if (!expressions.length) {
+        return make_node(AST_Number, this, { value: 0 });
+    }
+    return make_sequence(this, expressions);
+});
+
+def_drop_side_effect_free(AST_Expansion, function (compressor, first_in_statement) {
+    return this.expression.drop_side_effect_free(compressor, first_in_statement);
+});
+
+def_drop_side_effect_free(AST_TemplateSegment, return_null);
+
+def_drop_side_effect_free(AST_TemplateString, function (compressor) {
+    var values = trim(this.segments, compressor, first_in_statement);
+    return values && make_sequence(this, values);
+});

my-app/node_modules/terser/lib/compress/drop-unused.js

@@ -0,0 +1,482 @@
+/***********************************************************************
+
+  A JavaScript tokenizer / parser / beautifier / compressor.
+  https://github.com/mishoo/UglifyJS2
+
+  -------------------------------- (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.
+
+ ***********************************************************************/
+
+import {
+    AST_Accessor,
+    AST_Assign,
+    AST_BlockStatement,
+    AST_Class,
+    AST_ClassExpression,
+    AST_ClassStaticBlock,
+    AST_DefaultAssign,
+    AST_DefClass,
+    AST_Definitions,
+    AST_Defun,
+    AST_Destructuring,
+    AST_EmptyStatement,
+    AST_Expansion,
+    AST_Export,
+    AST_For,
+    AST_ForIn,
+    AST_Function,
+    AST_LabeledStatement,
+    AST_Lambda,
+    AST_Number,
+    AST_Scope,
+    AST_SimpleStatement,
+    AST_SymbolBlockDeclaration,
+    AST_SymbolCatch,
+    AST_SymbolDeclaration,
+    AST_SymbolFunarg,
+    AST_SymbolRef,
+    AST_SymbolVar,
+    AST_Toplevel,
+    AST_Unary,
+    AST_Var,
+
+    TreeTransformer,
+    TreeWalker,
+    walk,
+} from "../ast.js";
+import {
+    keep_name,
+    make_node,
+    map_add,
+    MAP,
+    remove,
+    return_false,
+} from "../utils/index.js";
+import { SymbolDef } from "../scope.js";
+
+import {
+    WRITE_ONLY,
+    UNUSED,
+
+    has_flag,
+    set_flag,
+} from "./compressor-flags.js";
+import {
+    make_sequence,
+    maintain_this_binding,
+    is_empty,
+    is_ref_of,
+    can_be_evicted_from_block,
+} from "./common.js";
+
+const r_keep_assign = /keep_assign/;
+
+/** Drop unused variables from this scope */
+AST_Scope.DEFMETHOD("drop_unused", function(compressor) {
+    if (!compressor.option("unused")) return;
+    if (compressor.has_directive("use asm")) return;
+    if (!this.variables) return; // not really a scope (eg: AST_Class)
+
+    var self = this;
+    if (self.pinned()) return;
+    var drop_funcs = !(self instanceof AST_Toplevel) || compressor.toplevel.funcs;
+    var drop_vars = !(self instanceof AST_Toplevel) || compressor.toplevel.vars;
+    const assign_as_unused = r_keep_assign.test(compressor.option("unused")) ? return_false : function(node) {
+        if (node instanceof AST_Assign
+            && !node.logical
+            && (has_flag(node, WRITE_ONLY) || node.operator == "=")
+        ) {
+            return node.left;
+        }
+        if (node instanceof AST_Unary && has_flag(node, WRITE_ONLY)) {
+            return node.expression;
+        }
+    };
+    var in_use_ids = new Map();
+    var fixed_ids = new Map();
+    if (self instanceof AST_Toplevel && compressor.top_retain) {
+        self.variables.forEach(function(def) {
+            if (compressor.top_retain(def)) {
+                in_use_ids.set(def.id, def);
+            }
+        });
+    }
+    var var_defs_by_id = new Map();
+    var initializations = new Map();
+    // pass 1: find out which symbols are directly used in
+    // this scope (not in nested scopes).
+    var scope = this;
+    var tw = new TreeWalker(function(node, descend) {
+        if (node instanceof AST_Lambda && node.uses_arguments && !tw.has_directive("use strict")) {
+            node.argnames.forEach(function(argname) {
+                if (!(argname instanceof AST_SymbolDeclaration)) return;
+                var def = argname.definition();
+                in_use_ids.set(def.id, def);
+            });
+        }
+        if (node === self) return;
+        if (node instanceof AST_Class) {
+            if (node.has_side_effects(compressor)) {
+                node.visit_nondeferred_class_parts(tw);
+            }
+        }
+        if (node instanceof AST_Defun || node instanceof AST_DefClass) {
+            var node_def = node.name.definition();
+            const in_export = tw.parent() instanceof AST_Export;
+            if (in_export || !drop_funcs && scope === self) {
+                if (node_def.global) {
+                    in_use_ids.set(node_def.id, node_def);
+                }
+            }
+
+            map_add(initializations, node_def.id, node);
+            return true; // don't go in nested scopes
+        }
+        // In the root scope, we drop things. In inner scopes, we just check for uses.
+        const in_root_scope = scope === self;
+        if (node instanceof AST_SymbolFunarg && in_root_scope) {
+            map_add(var_defs_by_id, node.definition().id, node);
+        }
+        if (node instanceof AST_Definitions && in_root_scope) {
+            const in_export = tw.parent() instanceof AST_Export;
+            node.definitions.forEach(function(def) {
+                if (def.name instanceof AST_SymbolVar) {
+                    map_add(var_defs_by_id, def.name.definition().id, def);
+                }
+                if (in_export || !drop_vars) {
+                    walk(def.name, node => {
+                        if (node instanceof AST_SymbolDeclaration) {
+                            const def = node.definition();
+                            if (def.global) {
+                                in_use_ids.set(def.id, def);
+                            }
+                        }
+                    });
+                }
+                if (def.name instanceof AST_Destructuring) {
+                    def.walk(tw);
+                }
+                if (def.name instanceof AST_SymbolDeclaration && def.value) {
+                    var node_def = def.name.definition();
+                    map_add(initializations, node_def.id, def.value);
+                    if (!node_def.chained && def.name.fixed_value() === def.value) {
+                        fixed_ids.set(node_def.id, def);
+                    }
+                    if (def.value.has_side_effects(compressor)) {
+                        def.value.walk(tw);
+                    }
+                }
+            });
+            return true;
+        }
+        return scan_ref_scoped(node, descend);
+    });
+    self.walk(tw);
+    // pass 2: for every used symbol we need to walk its
+    // initialization code to figure out if it uses other
+    // symbols (that may not be in_use).
+    tw = new TreeWalker(scan_ref_scoped);
+    in_use_ids.forEach(function (def) {
+        var init = initializations.get(def.id);
+        if (init) init.forEach(function(init) {
+            init.walk(tw);
+        });
+    });
+    // pass 3: we should drop declarations not in_use
+    var tt = new TreeTransformer(
+        function before(node, descend, in_list) {
+            var parent = tt.parent();
+            if (drop_vars) {
+                const sym = assign_as_unused(node);
+                if (sym instanceof AST_SymbolRef) {
+                    var def = sym.definition();
+                    var in_use = in_use_ids.has(def.id);
+                    if (node instanceof AST_Assign) {
+                        if (!in_use || fixed_ids.has(def.id) && fixed_ids.get(def.id) !== node) {
+                            return maintain_this_binding(parent, node, node.right.transform(tt));
+                        }
+                    } else if (!in_use) {
+                        return in_list ? MAP.skip : make_node(AST_Number, node, { value: 0 });
+                    }
+                }
+            }
+            if (scope !== self) return;
+            var def;
+            if (node.name
+                && (node instanceof AST_ClassExpression
+                    && !keep_name(compressor.option("keep_classnames"), (def = node.name.definition()).name)
+                || node instanceof AST_Function
+                    && !keep_name(compressor.option("keep_fnames"), (def = node.name.definition()).name))) {
+                // any declarations with same name will overshadow
+                // name of this anonymous function and can therefore
+                // never be used anywhere
+                if (!in_use_ids.has(def.id) || def.orig.length > 1) node.name = null;
+            }
+            if (node instanceof AST_Lambda && !(node instanceof AST_Accessor)) {
+                var trim = !compressor.option("keep_fargs");
+                for (var a = node.argnames, i = a.length; --i >= 0;) {
+                    var sym = a[i];
+                    if (sym instanceof AST_Expansion) {
+                        sym = sym.expression;
+                    }
+                    if (sym instanceof AST_DefaultAssign) {
+                        sym = sym.left;
+                    }
+                    // Do not drop destructuring arguments.
+                    // They constitute a type assertion of sorts
+                    if (
+                        !(sym instanceof AST_Destructuring)
+                        && !in_use_ids.has(sym.definition().id)
+                    ) {
+                        set_flag(sym, UNUSED);
+                        if (trim) {
+                            a.pop();
+                        }
+                    } else {
+                        trim = false;
+                    }
+                }
+            }
+            if (node instanceof AST_DefClass && node !== self) {
+                const def = node.name.definition();
+                descend(node, this);
+                const keep_class = def.global && !drop_funcs || in_use_ids.has(def.id);
+                if (!keep_class) {
+                    const kept = node.drop_side_effect_free(compressor);
+                    if (kept == null) {
+                        def.eliminated++;
+                        return in_list ? MAP.skip : make_node(AST_EmptyStatement, node);
+                    }
+                    return kept;
+                }
+                return node;
+            }
+            if (node instanceof AST_Defun && node !== self) {
+                const def = node.name.definition();
+                const keep = def.global && !drop_funcs || in_use_ids.has(def.id);
+                if (!keep) {
+                    def.eliminated++;
+                    return in_list ? MAP.skip : make_node(AST_EmptyStatement, node);
+                }
+            }
+            if (node instanceof AST_Definitions && !(parent instanceof AST_ForIn && parent.init === node)) {
+                var drop_block = !(parent instanceof AST_Toplevel) && !(node instanceof AST_Var);
+                // place uninitialized names at the start
+                var body = [], head = [], tail = [];
+                // for unused names whose initialization has
+                // side effects, we can cascade the init. code
+                // into the next one, or next statement.
+                var side_effects = [];
+                node.definitions.forEach(function(def) {
+                    if (def.value) def.value = def.value.transform(tt);
+                    var is_destructure = def.name instanceof AST_Destructuring;
+                    var sym = is_destructure
+                        ? new SymbolDef(null, { name: "<destructure>" }) /* fake SymbolDef */
+                        : def.name.definition();
+                    if (drop_block && sym.global) return tail.push(def);
+                    if (!(drop_vars || drop_block)
+                        || is_destructure
+                            && (def.name.names.length
+                                || def.name.is_array
+                                || compressor.option("pure_getters") != true)
+                        || in_use_ids.has(sym.id)
+                    ) {
+                        if (def.value && fixed_ids.has(sym.id) && fixed_ids.get(sym.id) !== def) {
+                            def.value = def.value.drop_side_effect_free(compressor);
+                        }
+                        if (def.name instanceof AST_SymbolVar) {
+                            var var_defs = var_defs_by_id.get(sym.id);
+                            if (var_defs.length > 1 && (!def.value || sym.orig.indexOf(def.name) > sym.eliminated)) {
+                                if (def.value) {
+                                    var ref = make_node(AST_SymbolRef, def.name, def.name);
+                                    sym.references.push(ref);
+                                    var assign = make_node(AST_Assign, def, {
+                                        operator: "=",
+                                        logical: false,
+                                        left: ref,
+                                        right: def.value
+                                    });
+                                    if (fixed_ids.get(sym.id) === def) {
+                                        fixed_ids.set(sym.id, assign);
+                                    }
+                                    side_effects.push(assign.transform(tt));
+                                }
+                                remove(var_defs, def);
+                                sym.eliminated++;
+                                return;
+                            }
+                        }
+                        if (def.value) {
+                            if (side_effects.length > 0) {
+                                if (tail.length > 0) {
+                                    side_effects.push(def.value);
+                                    def.value = make_sequence(def.value, side_effects);
+                                } else {
+                                    body.push(make_node(AST_SimpleStatement, node, {
+                                        body: make_sequence(node, side_effects)
+                                    }));
+                                }
+                                side_effects = [];
+                            }
+                            tail.push(def);
+                        } else {
+                            head.push(def);
+                        }
+                    } else if (sym.orig[0] instanceof AST_SymbolCatch) {
+                        var value = def.value && def.value.drop_side_effect_free(compressor);
+                        if (value) side_effects.push(value);
+                        def.value = null;
+                        head.push(def);
+                    } else {
+                        var value = def.value && def.value.drop_side_effect_free(compressor);
+                        if (value) {
+                            side_effects.push(value);
+                        }
+                        sym.eliminated++;
+                    }
+                });
+                if (head.length > 0 || tail.length > 0) {
+                    node.definitions = head.concat(tail);
+                    body.push(node);
+                }
+                if (side_effects.length > 0) {
+                    body.push(make_node(AST_SimpleStatement, node, {
+                        body: make_sequence(node, side_effects)
+                    }));
+                }
+                switch (body.length) {
+                  case 0:
+                    return in_list ? MAP.skip : make_node(AST_EmptyStatement, node);
+                  case 1:
+                    return body[0];
+                  default:
+                    return in_list ? MAP.splice(body) : make_node(AST_BlockStatement, node, { body });
+                }
+            }
+            // certain combination of unused name + side effect leads to:
+            //    https://github.com/mishoo/UglifyJS2/issues/44
+            //    https://github.com/mishoo/UglifyJS2/issues/1830
+            //    https://github.com/mishoo/UglifyJS2/issues/1838
+            // that's an invalid AST.
+            // We fix it at this stage by moving the `var` outside the `for`.
+            if (node instanceof AST_For) {
+                descend(node, this);
+                var block;
+                if (node.init instanceof AST_BlockStatement) {
+                    block = node.init;
+                    node.init = block.body.pop();
+                    block.body.push(node);
+                }
+                if (node.init instanceof AST_SimpleStatement) {
+                    node.init = node.init.body;
+                } else if (is_empty(node.init)) {
+                    node.init = null;
+                }
+                return !block ? node : in_list ? MAP.splice(block.body) : block;
+            }
+            if (node instanceof AST_LabeledStatement
+                && node.body instanceof AST_For
+            ) {
+                descend(node, this);
+                if (node.body instanceof AST_BlockStatement) {
+                    var block = node.body;
+                    node.body = block.body.pop();
+                    block.body.push(node);
+                    return in_list ? MAP.splice(block.body) : block;
+                }
+                return node;
+            }
+            if (node instanceof AST_BlockStatement) {
+                descend(node, this);
+                if (in_list && node.body.every(can_be_evicted_from_block)) {
+                    return MAP.splice(node.body);
+                }
+                return node;
+            }
+            if (node instanceof AST_Scope && !(node instanceof AST_ClassStaticBlock)) {
+                const save_scope = scope;
+                scope = node;
+                descend(node, this);
+                scope = save_scope;
+                return node;
+            }
+        }
+    );
+
+    self.transform(tt);
+
+    function scan_ref_scoped(node, descend) {
+        var node_def;
+        const sym = assign_as_unused(node);
+        if (sym instanceof AST_SymbolRef
+            && !is_ref_of(node.left, AST_SymbolBlockDeclaration)
+            && self.variables.get(sym.name) === (node_def = sym.definition())
+        ) {
+            if (node instanceof AST_Assign) {
+                node.right.walk(tw);
+                if (!node_def.chained && node.left.fixed_value() === node.right) {
+                    fixed_ids.set(node_def.id, node);
+                }
+            }
+            return true;
+        }
+        if (node instanceof AST_SymbolRef) {
+            node_def = node.definition();
+            if (!in_use_ids.has(node_def.id)) {
+                in_use_ids.set(node_def.id, node_def);
+                if (node_def.orig[0] instanceof AST_SymbolCatch) {
+                    const redef = node_def.scope.is_block_scope()
+                        && node_def.scope.get_defun_scope().variables.get(node_def.name);
+                    if (redef) in_use_ids.set(redef.id, redef);
+                }
+            }
+            return true;
+        }
+        if (node instanceof AST_Class) {
+            descend();
+            return true;
+        }
+        if (node instanceof AST_Scope && !(node instanceof AST_ClassStaticBlock)) {
+            var save_scope = scope;
+            scope = node;
+            descend();
+            scope = save_scope;
+            return true;
+        }
+    }
+});
+

my-app/node_modules/terser/lib/compress/evaluate.js

@@ -0,0 +1,488 @@
+/***********************************************************************
+
+  A JavaScript tokenizer / parser / beautifier / compressor.
+  https://github.com/mishoo/UglifyJS2
+
+  -------------------------------- (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.
+
+ ***********************************************************************/
+
+import {
+    HOP,
+    makePredicate,
+    return_this,
+    string_template,
+    regexp_source_fix,
+    regexp_is_safe,
+} from "../utils/index.js";
+import {
+    AST_Array,
+    AST_BigInt,
+    AST_Binary,
+    AST_Call,
+    AST_Chain,
+    AST_Class,
+    AST_Conditional,
+    AST_Constant,
+    AST_Dot,
+    AST_Expansion,
+    AST_Function,
+    AST_Lambda,
+    AST_New,
+    AST_Node,
+    AST_Object,
+    AST_PropAccess,
+    AST_RegExp,
+    AST_Statement,
+    AST_Symbol,
+    AST_SymbolRef,
+    AST_TemplateString,
+    AST_UnaryPrefix,
+    AST_With,
+} from "../ast.js";
+import { is_undeclared_ref} from "./inference.js";
+import { is_pure_native_value, is_pure_native_fn, is_pure_native_method } from "./native-objects.js";
+
+// methods to evaluate a constant expression
+
+function def_eval(node, func) {
+    node.DEFMETHOD("_eval", func);
+}
+
+// Used to propagate a nullish short-circuit signal upwards through the chain.
+export const nullish = Symbol("This AST_Chain is nullish");
+
+// If the node has been successfully reduced to a constant,
+// then its value is returned; otherwise the element itself
+// is returned.
+// They can be distinguished as constant value is never a
+// descendant of AST_Node.
+AST_Node.DEFMETHOD("evaluate", function (compressor) {
+    if (!compressor.option("evaluate"))
+        return this;
+    var val = this._eval(compressor, 1);
+    if (!val || val instanceof RegExp)
+        return val;
+    if (typeof val == "function" || typeof val == "object" || val == nullish)
+        return this;
+
+    // Evaluated strings can be larger than the original expression
+    if (typeof val === "string") {
+        const unevaluated_size = this.size(compressor);
+        if (val.length + 2 > unevaluated_size) return this;
+    }
+
+    return val;
+});
+
+var unaryPrefix = makePredicate("! ~ - + void");
+AST_Node.DEFMETHOD("is_constant", function () {
+    // Accomodate when compress option evaluate=false
+    // as well as the common constant expressions !0 and -1
+    if (this instanceof AST_Constant) {
+        return !(this instanceof AST_RegExp);
+    } else {
+        return this instanceof AST_UnaryPrefix
+            && this.expression instanceof AST_Constant
+            && unaryPrefix.has(this.operator);
+    }
+});
+
+def_eval(AST_Statement, function () {
+    throw new Error(string_template("Cannot evaluate a statement [{file}:{line},{col}]", this.start));
+});
+
+def_eval(AST_Lambda, return_this);
+def_eval(AST_Class, return_this);
+def_eval(AST_Node, return_this);
+def_eval(AST_Constant, function () {
+    return this.getValue();
+});
+
+def_eval(AST_BigInt, return_this);
+
+def_eval(AST_RegExp, function (compressor) {
+    let evaluated = compressor.evaluated_regexps.get(this.value);
+    if (evaluated === undefined && regexp_is_safe(this.value.source)) {
+        try {
+            const { source, flags } = this.value;
+            evaluated = new RegExp(source, flags);
+        } catch (e) {
+            evaluated = null;
+        }
+        compressor.evaluated_regexps.set(this.value, evaluated);
+    }
+    return evaluated || this;
+});
+
+def_eval(AST_TemplateString, function () {
+    if (this.segments.length !== 1) return this;
+    return this.segments[0].value;
+});
+
+def_eval(AST_Function, function (compressor) {
+    if (compressor.option("unsafe")) {
+        var fn = function () { };
+        fn.node = this;
+        fn.toString = () => this.print_to_string();
+        return fn;
+    }
+    return this;
+});
+
+def_eval(AST_Array, function (compressor, depth) {
+    if (compressor.option("unsafe")) {
+        var elements = [];
+        for (var i = 0, len = this.elements.length; i < len; i++) {
+            var element = this.elements[i];
+            var value = element._eval(compressor, depth);
+            if (element === value)
+                return this;
+            elements.push(value);
+        }
+        return elements;
+    }
+    return this;
+});
+
+def_eval(AST_Object, function (compressor, depth) {
+    if (compressor.option("unsafe")) {
+        var val = {};
+        for (var i = 0, len = this.properties.length; i < len; i++) {
+            var prop = this.properties[i];
+            if (prop instanceof AST_Expansion)
+                return this;
+            var key = prop.key;
+            if (key instanceof AST_Symbol) {
+                key = key.name;
+            } else if (key instanceof AST_Node) {
+                key = key._eval(compressor, depth);
+                if (key === prop.key)
+                    return this;
+            }
+            if (typeof Object.prototype[key] === "function") {
+                return this;
+            }
+            if (prop.value instanceof AST_Function)
+                continue;
+            val[key] = prop.value._eval(compressor, depth);
+            if (val[key] === prop.value)
+                return this;
+        }
+        return val;
+    }
+    return this;
+});
+
+var non_converting_unary = makePredicate("! typeof void");
+def_eval(AST_UnaryPrefix, function (compressor, depth) {
+    var e = this.expression;
+    // Function would be evaluated to an array and so typeof would
+    // incorrectly return 'object'. Hence making is a special case.
+    if (compressor.option("typeofs")
+        && this.operator == "typeof"
+        && (e instanceof AST_Lambda
+            || e instanceof AST_SymbolRef
+            && e.fixed_value() instanceof AST_Lambda)) {
+        return typeof function () { };
+    }
+    if (!non_converting_unary.has(this.operator))
+        depth++;
+    e = e._eval(compressor, depth);
+    if (e === this.expression)
+        return this;
+    switch (this.operator) {
+        case "!": return !e;
+        case "typeof":
+            // typeof <RegExp> returns "object" or "function" on different platforms
+            // so cannot evaluate reliably
+            if (e instanceof RegExp)
+                return this;
+            return typeof e;
+        case "void": return void e;
+        case "~": return ~e;
+        case "-": return -e;
+        case "+": return +e;
+    }
+    return this;
+});
+
+var non_converting_binary = makePredicate("&& || ?? === !==");
+const identity_comparison = makePredicate("== != === !==");
+const has_identity = value => typeof value === "object"
+    || typeof value === "function"
+    || typeof value === "symbol";
+
+def_eval(AST_Binary, function (compressor, depth) {
+    if (!non_converting_binary.has(this.operator))
+        depth++;
+
+    var left = this.left._eval(compressor, depth);
+    if (left === this.left)
+        return this;
+    var right = this.right._eval(compressor, depth);
+    if (right === this.right)
+        return this;
+    var result;
+
+    if (left != null
+        && right != null
+        && identity_comparison.has(this.operator)
+        && has_identity(left)
+        && has_identity(right)
+        && typeof left === typeof right) {
+        // Do not compare by reference
+        return this;
+    }
+
+    switch (this.operator) {
+        case "&&": result = left && right; break;
+        case "||": result = left || right; break;
+        case "??": result = left != null ? left : right; break;
+        case "|": result = left | right; break;
+        case "&": result = left & right; break;
+        case "^": result = left ^ right; break;
+        case "+": result = left + right; break;
+        case "*": result = left * right; break;
+        case "**": result = Math.pow(left, right); break;
+        case "/": result = left / right; break;
+        case "%": result = left % right; break;
+        case "-": result = left - right; break;
+        case "<<": result = left << right; break;
+        case ">>": result = left >> right; break;
+        case ">>>": result = left >>> right; break;
+        case "==": result = left == right; break;
+        case "===": result = left === right; break;
+        case "!=": result = left != right; break;
+        case "!==": result = left !== right; break;
+        case "<": result = left < right; break;
+        case "<=": result = left <= right; break;
+        case ">": result = left > right; break;
+        case ">=": result = left >= right; break;
+        default:
+            return this;
+    }
+    if (isNaN(result) && compressor.find_parent(AST_With)) {
+        // leave original expression as is
+        return this;
+    }
+    return result;
+});
+
+def_eval(AST_Conditional, function (compressor, depth) {
+    var condition = this.condition._eval(compressor, depth);
+    if (condition === this.condition)
+        return this;
+    var node = condition ? this.consequent : this.alternative;
+    var value = node._eval(compressor, depth);
+    return value === node ? this : value;
+});
+
+// Set of AST_SymbolRef which are currently being evaluated.
+// Avoids infinite recursion of ._eval()
+const reentrant_ref_eval = new Set();
+def_eval(AST_SymbolRef, function (compressor, depth) {
+    if (reentrant_ref_eval.has(this))
+        return this;
+
+    var fixed = this.fixed_value();
+    if (!fixed)
+        return this;
+
+    reentrant_ref_eval.add(this);
+    const value = fixed._eval(compressor, depth);
+    reentrant_ref_eval.delete(this);
+
+    if (value === fixed)
+        return this;
+
+    if (value && typeof value == "object") {
+        var escaped = this.definition().escaped;
+        if (escaped && depth > escaped)
+            return this;
+    }
+    return value;
+});
+
+const global_objs = { Array, Math, Number, Object, String };
+
+const regexp_flags = new Set([
+    "dotAll",
+    "global",
+    "ignoreCase",
+    "multiline",
+    "sticky",
+    "unicode",
+]);
+
+def_eval(AST_PropAccess, function (compressor, depth) {
+    let obj = this.expression._eval(compressor, depth + 1);
+    if (obj === nullish || (this.optional && obj == null)) return nullish;
+
+    // `.length` of strings and arrays is always safe
+    if (this.property === "length") {
+        if (typeof obj === "string") {
+            return obj.length;
+        }
+
+        const is_spreadless_array =
+            obj instanceof AST_Array
+            && obj.elements.every(el => !(el instanceof AST_Expansion));
+
+        if (
+            is_spreadless_array
+            && obj.elements.every(el => !el.has_side_effects(compressor))
+        ) {
+            return obj.elements.length;
+        }
+    }
+
+    if (compressor.option("unsafe")) {
+        var key = this.property;
+        if (key instanceof AST_Node) {
+            key = key._eval(compressor, depth);
+            if (key === this.property)
+                return this;
+        }
+
+        var exp = this.expression;
+        if (is_undeclared_ref(exp)) {
+            var aa;
+            var first_arg = exp.name === "hasOwnProperty"
+                && key === "call"
+                && (aa = compressor.parent() && compressor.parent().args)
+                && (aa && aa[0]
+                    && aa[0].evaluate(compressor));
+
+            first_arg = first_arg instanceof AST_Dot ? first_arg.expression : first_arg;
+
+            if (first_arg == null || first_arg.thedef && first_arg.thedef.undeclared) {
+                return this.clone();
+            }
+            if (!is_pure_native_value(exp.name, key))
+                return this;
+            obj = global_objs[exp.name];
+        } else {
+            if (obj instanceof RegExp) {
+                if (key == "source") {
+                    return regexp_source_fix(obj.source);
+                } else if (key == "flags" || regexp_flags.has(key)) {
+                    return obj[key];
+                }
+            }
+            if (!obj || obj === exp || !HOP(obj, key))
+                return this;
+
+            if (typeof obj == "function")
+                switch (key) {
+                    case "name":
+                        return obj.node.name ? obj.node.name.name : "";
+                    case "length":
+                        return obj.node.length_property();
+                    default:
+                        return this;
+                }
+        }
+        return obj[key];
+    }
+    return this;
+});
+
+def_eval(AST_Chain, function (compressor, depth) {
+    const evaluated = this.expression._eval(compressor, depth);
+    return evaluated === nullish
+        ? undefined
+        : evaluated === this.expression
+          ? this
+          : evaluated;
+});
+
+def_eval(AST_Call, function (compressor, depth) {
+    var exp = this.expression;
+
+    const callee = exp._eval(compressor, depth);
+    if (callee === nullish || (this.optional && callee == null)) return nullish;
+
+    if (compressor.option("unsafe") && exp instanceof AST_PropAccess) {
+        var key = exp.property;
+        if (key instanceof AST_Node) {
+            key = key._eval(compressor, depth);
+            if (key === exp.property)
+                return this;
+        }
+        var val;
+        var e = exp.expression;
+        if (is_undeclared_ref(e)) {
+            var first_arg = e.name === "hasOwnProperty" &&
+                key === "call" &&
+                (this.args[0] && this.args[0].evaluate(compressor));
+
+            first_arg = first_arg instanceof AST_Dot ? first_arg.expression : first_arg;
+
+            if ((first_arg == null || first_arg.thedef && first_arg.thedef.undeclared)) {
+                return this.clone();
+            }
+            if (!is_pure_native_fn(e.name, key)) return this;
+            val = global_objs[e.name];
+        } else {
+            val = e._eval(compressor, depth + 1);
+            if (val === e || !val)
+                return this;
+            if (!is_pure_native_method(val.constructor.name, key))
+                return this;
+        }
+        var args = [];
+        for (var i = 0, len = this.args.length; i < len; i++) {
+            var arg = this.args[i];
+            var value = arg._eval(compressor, depth);
+            if (arg === value)
+                return this;
+            if (arg instanceof AST_Lambda)
+                return this;
+            args.push(value);
+        }
+        try {
+            return val[key].apply(val, args);
+        } catch (ex) {
+            // We don't really care
+        }
+    }
+    return this;
+});
+
+// Also a subclass of AST_Call
+def_eval(AST_New, return_this);

my-app/node_modules/terser/lib/compress/global-defs.js

@@ -0,0 +1,92 @@
+import {
+    AST_Array,
+    AST_Chain,
+    AST_Constant,
+    AST_Dot,
+    AST_ImportMeta,
+    AST_Node,
+    AST_Object,
+    AST_ObjectKeyVal,
+    AST_PropAccess,
+    AST_SymbolDeclaration,
+    AST_SymbolRef,
+    AST_Toplevel,
+    TreeTransformer,
+} from "../ast.js";
+import { make_node, noop, HOP } from "../utils/index.js";
+import { make_node_from_constant } from "./common.js";
+import { is_lhs } from "./inference.js";
+
+(function(def_find_defs) {
+    function to_node(value, orig) {
+        if (value instanceof AST_Node) {
+            if (!(value instanceof AST_Constant)) {
+                // Value may be a function, an array including functions and even a complex assign / block expression,
+                // so it should never be shared in different places.
+                // Otherwise wrong information may be used in the compression phase
+                value = value.clone(true);
+            }
+            return make_node(value.CTOR, orig, value);
+        }
+        if (Array.isArray(value)) return make_node(AST_Array, orig, {
+            elements: value.map(function(value) {
+                return to_node(value, orig);
+            })
+        });
+        if (value && typeof value == "object") {
+            var props = [];
+            for (var key in value) if (HOP(value, key)) {
+                props.push(make_node(AST_ObjectKeyVal, orig, {
+                    key: key,
+                    value: to_node(value[key], orig)
+                }));
+            }
+            return make_node(AST_Object, orig, {
+                properties: props
+            });
+        }
+        return make_node_from_constant(value, orig);
+    }
+
+    AST_Toplevel.DEFMETHOD("resolve_defines", function(compressor) {
+        if (!compressor.option("global_defs")) return this;
+        this.figure_out_scope({ ie8: compressor.option("ie8") });
+        return this.transform(new TreeTransformer(function(node) {
+            var def = node._find_defs(compressor, "");
+            if (!def) return;
+            var level = 0, child = node, parent;
+            while (parent = this.parent(level++)) {
+                if (!(parent instanceof AST_PropAccess)) break;
+                if (parent.expression !== child) break;
+                child = parent;
+            }
+            if (is_lhs(child, parent)) {
+                return;
+            }
+            return def;
+        }));
+    });
+    def_find_defs(AST_Node, noop);
+    def_find_defs(AST_Chain, function(compressor, suffix) {
+        return this.expression._find_defs(compressor, suffix);
+    });
+    def_find_defs(AST_Dot, function(compressor, suffix) {
+        return this.expression._find_defs(compressor, "." + this.property + suffix);
+    });
+    def_find_defs(AST_SymbolDeclaration, function() {
+        if (!this.global()) return;
+    });
+    def_find_defs(AST_SymbolRef, function(compressor, suffix) {
+        if (!this.global()) return;
+        var defines = compressor.option("global_defs");
+        var name = this.name + suffix;
+        if (HOP(defines, name)) return to_node(defines[name], this);
+    });
+    def_find_defs(AST_ImportMeta, function(compressor, suffix) {
+        var defines = compressor.option("global_defs");
+        var name = "import.meta" + suffix;
+        if (HOP(defines, name)) return to_node(defines[name], this);
+    });
+})(function(node, func) {
+    node.DEFMETHOD("_find_defs", func);
+});

my-app/node_modules/terser/lib/compress/inference.js

@@ -0,0 +1,934 @@
+/***********************************************************************
+
+  A JavaScript tokenizer / parser / beautifier / compressor.
+  https://github.com/mishoo/UglifyJS2
+
+  -------------------------------- (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.
+
+ ***********************************************************************/
+
+import {
+  AST_Array,
+  AST_Arrow,
+  AST_Assign,
+  AST_BigInt,
+  AST_Binary,
+  AST_Block,
+  AST_BlockStatement,
+  AST_Call,
+  AST_Case,
+  AST_Chain,
+  AST_Class,
+  AST_DefClass,
+  AST_ClassStaticBlock,
+  AST_ClassProperty,
+  AST_ConciseMethod,
+  AST_Conditional,
+  AST_Constant,
+  AST_Definitions,
+  AST_Dot,
+  AST_EmptyStatement,
+  AST_Expansion,
+  AST_False,
+  AST_ForIn,
+  AST_Function,
+  AST_If,
+  AST_Import,
+  AST_ImportMeta,
+  AST_Jump,
+  AST_LabeledStatement,
+  AST_Lambda,
+  AST_New,
+  AST_Node,
+  AST_Null,
+  AST_Number,
+  AST_Object,
+  AST_ObjectGetter,
+  AST_ObjectKeyVal,
+  AST_ObjectProperty,
+  AST_ObjectSetter,
+  AST_PropAccess,
+  AST_RegExp,
+  AST_Return,
+  AST_Scope,
+  AST_Sequence,
+  AST_SimpleStatement,
+  AST_Statement,
+  AST_String,
+  AST_Sub,
+  AST_Switch,
+  AST_SwitchBranch,
+  AST_SymbolClassProperty,
+  AST_SymbolDeclaration,
+  AST_SymbolRef,
+  AST_TemplateSegment,
+  AST_TemplateString,
+  AST_This,
+  AST_True,
+  AST_Try,
+  AST_Unary,
+  AST_UnaryPostfix,
+  AST_UnaryPrefix,
+  AST_Undefined,
+  AST_VarDef,
+
+  walk,
+  walk_abort,
+
+  _PURE
+} from "../ast.js";
+import {
+    makePredicate,
+    return_true,
+    return_false,
+    return_null,
+    return_this,
+    make_node,
+    member,
+    has_annotation,
+} from "../utils/index.js";
+import { make_sequence, best_of_expression, read_property } from "./common.js";
+
+import { INLINED, UNDEFINED, has_flag } from "./compressor-flags.js";
+import { pure_prop_access_globals, is_pure_native_fn, is_pure_native_method } from "./native-objects.js";
+
+// Functions and methods to infer certain facts about expressions
+// It's not always possible to be 100% sure about something just by static analysis,
+// so `true` means yes, and `false` means maybe
+
+export const is_undeclared_ref = (node) =>
+    node instanceof AST_SymbolRef && node.definition().undeclared;
+
+export const lazy_op = makePredicate("&& || ??");
+export const unary_side_effects = makePredicate("delete ++ --");
+
+// methods to determine whether an expression has a boolean result type
+(function(def_is_boolean) {
+    const unary_bool = makePredicate("! delete");
+    const binary_bool = makePredicate("in instanceof == != === !== < <= >= >");
+    def_is_boolean(AST_Node, return_false);
+    def_is_boolean(AST_UnaryPrefix, function() {
+        return unary_bool.has(this.operator);
+    });
+    def_is_boolean(AST_Binary, function() {
+        return binary_bool.has(this.operator)
+            || lazy_op.has(this.operator)
+                && this.left.is_boolean()
+                && this.right.is_boolean();
+    });
+    def_is_boolean(AST_Conditional, function() {
+        return this.consequent.is_boolean() && this.alternative.is_boolean();
+    });
+    def_is_boolean(AST_Assign, function() {
+        return this.operator == "=" && this.right.is_boolean();
+    });
+    def_is_boolean(AST_Sequence, function() {
+        return this.tail_node().is_boolean();
+    });
+    def_is_boolean(AST_True, return_true);
+    def_is_boolean(AST_False, return_true);
+})(function(node, func) {
+    node.DEFMETHOD("is_boolean", func);
+});
+
+// methods to determine if an expression has a numeric result type
+(function(def_is_number) {
+    def_is_number(AST_Node, return_false);
+    def_is_number(AST_Number, return_true);
+    const unary = makePredicate("+ - ~ ++ --");
+    def_is_number(AST_Unary, function() {
+        return unary.has(this.operator) && !(this.expression instanceof AST_BigInt);
+    });
+    const numeric_ops = makePredicate("- * / % & | ^ << >> >>>");
+    def_is_number(AST_Binary, function(compressor) {
+        return numeric_ops.has(this.operator) || this.operator == "+"
+            && this.left.is_number(compressor)
+            && this.right.is_number(compressor);
+    });
+    def_is_number(AST_Assign, function(compressor) {
+        return numeric_ops.has(this.operator.slice(0, -1))
+            || this.operator == "=" && this.right.is_number(compressor);
+    });
+    def_is_number(AST_Sequence, function(compressor) {
+        return this.tail_node().is_number(compressor);
+    });
+    def_is_number(AST_Conditional, function(compressor) {
+        return this.consequent.is_number(compressor) && this.alternative.is_number(compressor);
+    });
+})(function(node, func) {
+    node.DEFMETHOD("is_number", func);
+});
+
+// methods to determine if an expression has a string result type
+(function(def_is_string) {
+    def_is_string(AST_Node, return_false);
+    def_is_string(AST_String, return_true);
+    def_is_string(AST_TemplateString, return_true);
+    def_is_string(AST_UnaryPrefix, function() {
+        return this.operator == "typeof";
+    });
+    def_is_string(AST_Binary, function(compressor) {
+        return this.operator == "+" &&
+            (this.left.is_string(compressor) || this.right.is_string(compressor));
+    });
+    def_is_string(AST_Assign, function(compressor) {
+        return (this.operator == "=" || this.operator == "+=") && this.right.is_string(compressor);
+    });
+    def_is_string(AST_Sequence, function(compressor) {
+        return this.tail_node().is_string(compressor);
+    });
+    def_is_string(AST_Conditional, function(compressor) {
+        return this.consequent.is_string(compressor) && this.alternative.is_string(compressor);
+    });
+})(function(node, func) {
+    node.DEFMETHOD("is_string", func);
+});
+
+export function is_undefined(node, compressor) {
+    return (
+        has_flag(node, UNDEFINED)
+        || node instanceof AST_Undefined
+        || node instanceof AST_UnaryPrefix
+            && node.operator == "void"
+            && !node.expression.has_side_effects(compressor)
+    );
+}
+
+// Is the node explicitly null or undefined.
+function is_null_or_undefined(node, compressor) {
+    let fixed;
+    return (
+        node instanceof AST_Null
+        || is_undefined(node, compressor)
+        || (
+            node instanceof AST_SymbolRef
+            && (fixed = node.definition().fixed) instanceof AST_Node
+            && is_nullish(fixed, compressor)
+        )
+    );
+}
+
+// Find out if this expression is optionally chained from a base-point that we
+// can statically analyze as null or undefined.
+export function is_nullish_shortcircuited(node, compressor) {
+    if (node instanceof AST_PropAccess || node instanceof AST_Call) {
+        return (
+            (node.optional && is_null_or_undefined(node.expression, compressor))
+            || is_nullish_shortcircuited(node.expression, compressor)
+        );
+    }
+    if (node instanceof AST_Chain) return is_nullish_shortcircuited(node.expression, compressor);
+    return false;
+}
+
+// Find out if something is == null, or can short circuit into nullish.
+// Used to optimize ?. and ??
+export function is_nullish(node, compressor) {
+    if (is_null_or_undefined(node, compressor)) return true;
+    return is_nullish_shortcircuited(node, compressor);
+}
+
+// Determine if expression might cause side effects
+// If there's a possibility that a node may change something when it's executed, this returns true
+(function(def_has_side_effects) {
+    def_has_side_effects(AST_Node, return_true);
+
+    def_has_side_effects(AST_EmptyStatement, return_false);
+    def_has_side_effects(AST_Constant, return_false);
+    def_has_side_effects(AST_This, return_false);
+
+    function any(list, compressor) {
+        for (var i = list.length; --i >= 0;)
+            if (list[i].has_side_effects(compressor))
+                return true;
+        return false;
+    }
+
+    def_has_side_effects(AST_Block, function(compressor) {
+        return any(this.body, compressor);
+    });
+    def_has_side_effects(AST_Call, function(compressor) {
+        if (
+            !this.is_callee_pure(compressor)
+            && (!this.expression.is_call_pure(compressor)
+                || this.expression.has_side_effects(compressor))
+        ) {
+            return true;
+        }
+        return any(this.args, compressor);
+    });
+    def_has_side_effects(AST_Switch, function(compressor) {
+        return this.expression.has_side_effects(compressor)
+            || any(this.body, compressor);
+    });
+    def_has_side_effects(AST_Case, function(compressor) {
+        return this.expression.has_side_effects(compressor)
+            || any(this.body, compressor);
+    });
+    def_has_side_effects(AST_Try, function(compressor) {
+        return this.body.has_side_effects(compressor)
+            || this.bcatch && this.bcatch.has_side_effects(compressor)
+            || this.bfinally && this.bfinally.has_side_effects(compressor);
+    });
+    def_has_side_effects(AST_If, function(compressor) {
+        return this.condition.has_side_effects(compressor)
+            || this.body && this.body.has_side_effects(compressor)
+            || this.alternative && this.alternative.has_side_effects(compressor);
+    });
+    def_has_side_effects(AST_ImportMeta, return_false);
+    def_has_side_effects(AST_LabeledStatement, function(compressor) {
+        return this.body.has_side_effects(compressor);
+    });
+    def_has_side_effects(AST_SimpleStatement, function(compressor) {
+        return this.body.has_side_effects(compressor);
+    });
+    def_has_side_effects(AST_Lambda, return_false);
+    def_has_side_effects(AST_Class, function (compressor) {
+        if (this.extends && this.extends.has_side_effects(compressor)) {
+            return true;
+        }
+        return any(this.properties, compressor);
+    });
+    def_has_side_effects(AST_ClassStaticBlock, function(compressor) {
+        return any(this.body, compressor);
+    });
+    def_has_side_effects(AST_Binary, function(compressor) {
+        return this.left.has_side_effects(compressor)
+            || this.right.has_side_effects(compressor);
+    });
+    def_has_side_effects(AST_Assign, return_true);
+    def_has_side_effects(AST_Conditional, function(compressor) {
+        return this.condition.has_side_effects(compressor)
+            || this.consequent.has_side_effects(compressor)
+            || this.alternative.has_side_effects(compressor);
+    });
+    def_has_side_effects(AST_Unary, function(compressor) {
+        return unary_side_effects.has(this.operator)
+            || this.expression.has_side_effects(compressor);
+    });
+    def_has_side_effects(AST_SymbolRef, function(compressor) {
+        return !this.is_declared(compressor) && !pure_prop_access_globals.has(this.name);
+    });
+    def_has_side_effects(AST_SymbolClassProperty, return_false);
+    def_has_side_effects(AST_SymbolDeclaration, return_false);
+    def_has_side_effects(AST_Object, function(compressor) {
+        return any(this.properties, compressor);
+    });
+    def_has_side_effects(AST_ObjectProperty, function(compressor) {
+        return (
+            this.computed_key() && this.key.has_side_effects(compressor)
+            || this.value && this.value.has_side_effects(compressor)
+        );
+    });
+    def_has_side_effects(AST_ClassProperty, function(compressor) {
+        return (
+            this.computed_key() && this.key.has_side_effects(compressor)
+            || this.static && this.value && this.value.has_side_effects(compressor)
+        );
+    });
+    def_has_side_effects(AST_ConciseMethod, function(compressor) {
+        return this.computed_key() && this.key.has_side_effects(compressor);
+    });
+    def_has_side_effects(AST_ObjectGetter, function(compressor) {
+        return this.computed_key() && this.key.has_side_effects(compressor);
+    });
+    def_has_side_effects(AST_ObjectSetter, function(compressor) {
+        return this.computed_key() && this.key.has_side_effects(compressor);
+    });
+    def_has_side_effects(AST_Array, function(compressor) {
+        return any(this.elements, compressor);
+    });
+    def_has_side_effects(AST_Dot, function(compressor) {
+        if (is_nullish(this, compressor)) {
+            return this.expression.has_side_effects(compressor);
+        }
+        if (!this.optional && this.expression.may_throw_on_access(compressor)) {
+            return true;
+        }
+
+        return this.expression.has_side_effects(compressor);
+    });
+    def_has_side_effects(AST_Sub, function(compressor) {
+        if (is_nullish(this, compressor)) {
+            return this.expression.has_side_effects(compressor);
+        }
+        if (!this.optional && this.expression.may_throw_on_access(compressor)) {
+            return true;
+        }
+
+        var property = this.property.has_side_effects(compressor);
+        if (property && this.optional) return true; // "?." is a condition
+
+        return property || this.expression.has_side_effects(compressor);
+    });
+    def_has_side_effects(AST_Chain, function (compressor) {
+        return this.expression.has_side_effects(compressor);
+    });
+    def_has_side_effects(AST_Sequence, function(compressor) {
+        return any(this.expressions, compressor);
+    });
+    def_has_side_effects(AST_Definitions, function(compressor) {
+        return any(this.definitions, compressor);
+    });
+    def_has_side_effects(AST_VarDef, function() {
+        return this.value;
+    });
+    def_has_side_effects(AST_TemplateSegment, return_false);
+    def_has_side_effects(AST_TemplateString, function(compressor) {
+        return any(this.segments, compressor);
+    });
+})(function(node, func) {
+    node.DEFMETHOD("has_side_effects", func);
+});
+
+// determine if expression may throw
+(function(def_may_throw) {
+    def_may_throw(AST_Node, return_true);
+
+    def_may_throw(AST_Constant, return_false);
+    def_may_throw(AST_EmptyStatement, return_false);
+    def_may_throw(AST_Lambda, return_false);
+    def_may_throw(AST_SymbolDeclaration, return_false);
+    def_may_throw(AST_This, return_false);
+    def_may_throw(AST_ImportMeta, return_false);
+
+    function any(list, compressor) {
+        for (var i = list.length; --i >= 0;)
+            if (list[i].may_throw(compressor))
+                return true;
+        return false;
+    }
+
+    def_may_throw(AST_Class, function(compressor) {
+        if (this.extends && this.extends.may_throw(compressor)) return true;
+        return any(this.properties, compressor);
+    });
+    def_may_throw(AST_ClassStaticBlock, function (compressor) {
+        return any(this.body, compressor);
+    });
+
+    def_may_throw(AST_Array, function(compressor) {
+        return any(this.elements, compressor);
+    });
+    def_may_throw(AST_Assign, function(compressor) {
+        if (this.right.may_throw(compressor)) return true;
+        if (!compressor.has_directive("use strict")
+            && this.operator == "="
+            && this.left instanceof AST_SymbolRef) {
+            return false;
+        }
+        return this.left.may_throw(compressor);
+    });
+    def_may_throw(AST_Binary, function(compressor) {
+        return this.left.may_throw(compressor)
+            || this.right.may_throw(compressor);
+    });
+    def_may_throw(AST_Block, function(compressor) {
+        return any(this.body, compressor);
+    });
+    def_may_throw(AST_Call, function(compressor) {
+        if (is_nullish(this, compressor)) return false;
+        if (any(this.args, compressor)) return true;
+        if (this.is_callee_pure(compressor)) return false;
+        if (this.expression.may_throw(compressor)) return true;
+        return !(this.expression instanceof AST_Lambda)
+            || any(this.expression.body, compressor);
+    });
+    def_may_throw(AST_Case, function(compressor) {
+        return this.expression.may_throw(compressor)
+            || any(this.body, compressor);
+    });
+    def_may_throw(AST_Conditional, function(compressor) {
+        return this.condition.may_throw(compressor)
+            || this.consequent.may_throw(compressor)
+            || this.alternative.may_throw(compressor);
+    });
+    def_may_throw(AST_Definitions, function(compressor) {
+        return any(this.definitions, compressor);
+    });
+    def_may_throw(AST_If, function(compressor) {
+        return this.condition.may_throw(compressor)
+            || this.body && this.body.may_throw(compressor)
+            || this.alternative && this.alternative.may_throw(compressor);
+    });
+    def_may_throw(AST_LabeledStatement, function(compressor) {
+        return this.body.may_throw(compressor);
+    });
+    def_may_throw(AST_Object, function(compressor) {
+        return any(this.properties, compressor);
+    });
+    def_may_throw(AST_ObjectProperty, function(compressor) {
+        // TODO key may throw too
+        return this.value ? this.value.may_throw(compressor) : false;
+    });
+    def_may_throw(AST_ClassProperty, function(compressor) {
+        return (
+            this.computed_key() && this.key.may_throw(compressor)
+            || this.static && this.value && this.value.may_throw(compressor)
+        );
+    });
+    def_may_throw(AST_ConciseMethod, function(compressor) {
+        return this.computed_key() && this.key.may_throw(compressor);
+    });
+    def_may_throw(AST_ObjectGetter, function(compressor) {
+        return this.computed_key() && this.key.may_throw(compressor);
+    });
+    def_may_throw(AST_ObjectSetter, function(compressor) {
+        return this.computed_key() && this.key.may_throw(compressor);
+    });
+    def_may_throw(AST_Return, function(compressor) {
+        return this.value && this.value.may_throw(compressor);
+    });
+    def_may_throw(AST_Sequence, function(compressor) {
+        return any(this.expressions, compressor);
+    });
+    def_may_throw(AST_SimpleStatement, function(compressor) {
+        return this.body.may_throw(compressor);
+    });
+    def_may_throw(AST_Dot, function(compressor) {
+        if (is_nullish(this, compressor)) return false;
+        return !this.optional && this.expression.may_throw_on_access(compressor)
+            || this.expression.may_throw(compressor);
+    });
+    def_may_throw(AST_Sub, function(compressor) {
+        if (is_nullish(this, compressor)) return false;
+        return !this.optional && this.expression.may_throw_on_access(compressor)
+            || this.expression.may_throw(compressor)
+            || this.property.may_throw(compressor);
+    });
+    def_may_throw(AST_Chain, function(compressor) {
+        return this.expression.may_throw(compressor);
+    });
+    def_may_throw(AST_Switch, function(compressor) {
+        return this.expression.may_throw(compressor)
+            || any(this.body, compressor);
+    });
+    def_may_throw(AST_SymbolRef, function(compressor) {
+        return !this.is_declared(compressor) && !pure_prop_access_globals.has(this.name);
+    });
+    def_may_throw(AST_SymbolClassProperty, return_false);
+    def_may_throw(AST_Try, function(compressor) {
+        return this.bcatch ? this.bcatch.may_throw(compressor) : this.body.may_throw(compressor)
+            || this.bfinally && this.bfinally.may_throw(compressor);
+    });
+    def_may_throw(AST_Unary, function(compressor) {
+        if (this.operator == "typeof" && this.expression instanceof AST_SymbolRef)
+            return false;
+        return this.expression.may_throw(compressor);
+    });
+    def_may_throw(AST_VarDef, function(compressor) {
+        if (!this.value) return false;
+        return this.value.may_throw(compressor);
+    });
+})(function(node, func) {
+    node.DEFMETHOD("may_throw", func);
+});
+
+// determine if expression is constant
+(function(def_is_constant_expression) {
+    function all_refs_local(scope) {
+        let result = true;
+        walk(this, node => {
+            if (node instanceof AST_SymbolRef) {
+                if (has_flag(this, INLINED)) {
+                    result = false;
+                    return walk_abort;
+                }
+                var def = node.definition();
+                if (
+                    member(def, this.enclosed)
+                    && !this.variables.has(def.name)
+                ) {
+                    if (scope) {
+                        var scope_def = scope.find_variable(node);
+                        if (def.undeclared ? !scope_def : scope_def === def) {
+                            result = "f";
+                            return true;
+                        }
+                    }
+                    result = false;
+                    return walk_abort;
+                }
+                return true;
+            }
+            if (node instanceof AST_This && this instanceof AST_Arrow) {
+                result = false;
+                return walk_abort;
+            }
+        });
+        return result;
+    }
+
+    def_is_constant_expression(AST_Node, return_false);
+    def_is_constant_expression(AST_Constant, return_true);
+    def_is_constant_expression(AST_Class, function(scope) {
+        if (this.extends && !this.extends.is_constant_expression(scope)) {
+            return false;
+        }
+
+        for (const prop of this.properties) {
+            if (prop.computed_key() && !prop.key.is_constant_expression(scope)) {
+                return false;
+            }
+            if (prop.static && prop.value && !prop.value.is_constant_expression(scope)) {
+                return false;
+            }
+            if (prop instanceof AST_ClassStaticBlock) {
+                return false;
+            }
+        }
+
+        return all_refs_local.call(this, scope);
+    });
+    def_is_constant_expression(AST_Lambda, all_refs_local);
+    def_is_constant_expression(AST_Unary, function() {
+        return this.expression.is_constant_expression();
+    });
+    def_is_constant_expression(AST_Binary, function() {
+        return this.left.is_constant_expression()
+            && this.right.is_constant_expression();
+    });
+    def_is_constant_expression(AST_Array, function() {
+        return this.elements.every((l) => l.is_constant_expression());
+    });
+    def_is_constant_expression(AST_Object, function() {
+        return this.properties.every((l) => l.is_constant_expression());
+    });
+    def_is_constant_expression(AST_ObjectProperty, function() {
+        return !!(!(this.key instanceof AST_Node) && this.value && this.value.is_constant_expression());
+    });
+})(function(node, func) {
+    node.DEFMETHOD("is_constant_expression", func);
+});
+
+
+// may_throw_on_access()
+// returns true if this node may be null, undefined or contain `AST_Accessor`
+(function(def_may_throw_on_access) {
+    AST_Node.DEFMETHOD("may_throw_on_access", function(compressor) {
+        return !compressor.option("pure_getters")
+            || this._dot_throw(compressor);
+    });
+
+    function is_strict(compressor) {
+        return /strict/.test(compressor.option("pure_getters"));
+    }
+
+    def_may_throw_on_access(AST_Node, is_strict);
+    def_may_throw_on_access(AST_Null, return_true);
+    def_may_throw_on_access(AST_Undefined, return_true);
+    def_may_throw_on_access(AST_Constant, return_false);
+    def_may_throw_on_access(AST_Array, return_false);
+    def_may_throw_on_access(AST_Object, function(compressor) {
+        if (!is_strict(compressor)) return false;
+        for (var i = this.properties.length; --i >=0;)
+            if (this.properties[i]._dot_throw(compressor)) return true;
+        return false;
+    });
+    // Do not be as strict with classes as we are with objects.
+    // Hopefully the community is not going to abuse static getters and setters.
+    // https://github.com/terser/terser/issues/724#issuecomment-643655656
+    def_may_throw_on_access(AST_Class, return_false);
+    def_may_throw_on_access(AST_ObjectProperty, return_false);
+    def_may_throw_on_access(AST_ObjectGetter, return_true);
+    def_may_throw_on_access(AST_Expansion, function(compressor) {
+        return this.expression._dot_throw(compressor);
+    });
+    def_may_throw_on_access(AST_Function, return_false);
+    def_may_throw_on_access(AST_Arrow, return_false);
+    def_may_throw_on_access(AST_UnaryPostfix, return_false);
+    def_may_throw_on_access(AST_UnaryPrefix, function() {
+        return this.operator == "void";
+    });
+    def_may_throw_on_access(AST_Binary, function(compressor) {
+        return (this.operator == "&&" || this.operator == "||" || this.operator == "??")
+            && (this.left._dot_throw(compressor) || this.right._dot_throw(compressor));
+    });
+    def_may_throw_on_access(AST_Assign, function(compressor) {
+        if (this.logical) return true;
+
+        return this.operator == "="
+            && this.right._dot_throw(compressor);
+    });
+    def_may_throw_on_access(AST_Conditional, function(compressor) {
+        return this.consequent._dot_throw(compressor)
+            || this.alternative._dot_throw(compressor);
+    });
+    def_may_throw_on_access(AST_Dot, function(compressor) {
+        if (!is_strict(compressor)) return false;
+
+        if (this.property == "prototype") {
+            return !(
+                this.expression instanceof AST_Function
+                || this.expression instanceof AST_Class
+            );
+        }
+        return true;
+    });
+    def_may_throw_on_access(AST_Chain, function(compressor) {
+        return this.expression._dot_throw(compressor);
+    });
+    def_may_throw_on_access(AST_Sequence, function(compressor) {
+        return this.tail_node()._dot_throw(compressor);
+    });
+    def_may_throw_on_access(AST_SymbolRef, function(compressor) {
+        if (this.name === "arguments" && this.scope instanceof AST_Lambda) return false;
+        if (has_flag(this, UNDEFINED)) return true;
+        if (!is_strict(compressor)) return false;
+        if (is_undeclared_ref(this) && this.is_declared(compressor)) return false;
+        if (this.is_immutable()) return false;
+        var fixed = this.fixed_value();
+        return !fixed || fixed._dot_throw(compressor);
+    });
+})(function(node, func) {
+    node.DEFMETHOD("_dot_throw", func);
+});
+
+export function is_lhs(node, parent) {
+    if (parent instanceof AST_Unary && unary_side_effects.has(parent.operator)) return parent.expression;
+    if (parent instanceof AST_Assign && parent.left === node) return node;
+    if (parent instanceof AST_ForIn && parent.init === node) return node;
+}
+
+// method to negate an expression
+(function(def_negate) {
+    function basic_negation(exp) {
+        return make_node(AST_UnaryPrefix, exp, {
+            operator: "!",
+            expression: exp
+        });
+    }
+    function best(orig, alt, first_in_statement) {
+        var negated = basic_negation(orig);
+        if (first_in_statement) {
+            var stat = make_node(AST_SimpleStatement, alt, {
+                body: alt
+            });
+            return best_of_expression(negated, stat) === stat ? alt : negated;
+        }
+        return best_of_expression(negated, alt);
+    }
+    def_negate(AST_Node, function() {
+        return basic_negation(this);
+    });
+    def_negate(AST_Statement, function() {
+        throw new Error("Cannot negate a statement");
+    });
+    def_negate(AST_Function, function() {
+        return basic_negation(this);
+    });
+    def_negate(AST_Class, function() {
+        return basic_negation(this);
+    });
+    def_negate(AST_Arrow, function() {
+        return basic_negation(this);
+    });
+    def_negate(AST_UnaryPrefix, function() {
+        if (this.operator == "!")
+            return this.expression;
+        return basic_negation(this);
+    });
+    def_negate(AST_Sequence, function(compressor) {
+        var expressions = this.expressions.slice();
+        expressions.push(expressions.pop().negate(compressor));
+        return make_sequence(this, expressions);
+    });
+    def_negate(AST_Conditional, function(compressor, first_in_statement) {
+        var self = this.clone();
+        self.consequent = self.consequent.negate(compressor);
+        self.alternative = self.alternative.negate(compressor);
+        return best(this, self, first_in_statement);
+    });
+    def_negate(AST_Binary, function(compressor, first_in_statement) {
+        var self = this.clone(), op = this.operator;
+        if (compressor.option("unsafe_comps")) {
+            switch (op) {
+              case "<=" : self.operator = ">"  ; return self;
+              case "<"  : self.operator = ">=" ; return self;
+              case ">=" : self.operator = "<"  ; return self;
+              case ">"  : self.operator = "<=" ; return self;
+            }
+        }
+        switch (op) {
+          case "==" : self.operator = "!="; return self;
+          case "!=" : self.operator = "=="; return self;
+          case "===": self.operator = "!=="; return self;
+          case "!==": self.operator = "==="; return self;
+          case "&&":
+            self.operator = "||";
+            self.left = self.left.negate(compressor, first_in_statement);
+            self.right = self.right.negate(compressor);
+            return best(this, self, first_in_statement);
+          case "||":
+            self.operator = "&&";
+            self.left = self.left.negate(compressor, first_in_statement);
+            self.right = self.right.negate(compressor);
+            return best(this, self, first_in_statement);
+        }
+        return basic_negation(this);
+    });
+})(function(node, func) {
+    node.DEFMETHOD("negate", function(compressor, first_in_statement) {
+        return func.call(this, compressor, first_in_statement);
+    });
+});
+
+// Is the callee of this function pure?
+var global_pure_fns = makePredicate("Boolean decodeURI decodeURIComponent Date encodeURI encodeURIComponent Error escape EvalError isFinite isNaN Number Object parseFloat parseInt RangeError ReferenceError String SyntaxError TypeError unescape URIError");
+AST_Call.DEFMETHOD("is_callee_pure", function(compressor) {
+    if (compressor.option("unsafe")) {
+        var expr = this.expression;
+        var first_arg = (this.args && this.args[0] && this.args[0].evaluate(compressor));
+        if (
+            expr.expression && expr.expression.name === "hasOwnProperty" &&
+            (first_arg == null || first_arg.thedef && first_arg.thedef.undeclared)
+        ) {
+            return false;
+        }
+        if (is_undeclared_ref(expr) && global_pure_fns.has(expr.name)) return true;
+        if (
+            expr instanceof AST_Dot
+            && is_undeclared_ref(expr.expression)
+            && is_pure_native_fn(expr.expression.name, expr.property)
+        ) {
+            return true;
+        }
+    }
+    if ((this instanceof AST_New) && compressor.option("pure_new")) {
+        return true;
+    }
+    if (compressor.option("side_effects") && has_annotation(this, _PURE)) {
+        return true;
+    }
+    return !compressor.pure_funcs(this);
+});
+
+// If I call this, is it a pure function?
+AST_Node.DEFMETHOD("is_call_pure", return_false);
+AST_Dot.DEFMETHOD("is_call_pure", function(compressor) {
+    if (!compressor.option("unsafe")) return;
+    const expr = this.expression;
+
+    let native_obj;
+    if (expr instanceof AST_Array) {
+        native_obj = "Array";
+    } else if (expr.is_boolean()) {
+        native_obj = "Boolean";
+    } else if (expr.is_number(compressor)) {
+        native_obj = "Number";
+    } else if (expr instanceof AST_RegExp) {
+        native_obj = "RegExp";
+    } else if (expr.is_string(compressor)) {
+        native_obj = "String";
+    } else if (!this.may_throw_on_access(compressor)) {
+        native_obj = "Object";
+    }
+    return native_obj != null && is_pure_native_method(native_obj, this.property);
+});
+
+// tell me if a statement aborts
+export const aborts = (thing) => thing && thing.aborts();
+
+(function(def_aborts) {
+    def_aborts(AST_Statement, return_null);
+    def_aborts(AST_Jump, return_this);
+    function block_aborts() {
+        for (var i = 0; i < this.body.length; i++) {
+            if (aborts(this.body[i])) {
+                return this.body[i];
+            }
+        }
+        return null;
+    }
+    def_aborts(AST_Import, return_null);
+    def_aborts(AST_BlockStatement, block_aborts);
+    def_aborts(AST_SwitchBranch, block_aborts);
+    def_aborts(AST_DefClass, function () {
+        for (const prop of this.properties) {
+            if (prop instanceof AST_ClassStaticBlock) {
+                if (prop.aborts()) return prop;
+            }
+        }
+        return null;
+    });
+    def_aborts(AST_ClassStaticBlock, block_aborts);
+    def_aborts(AST_If, function() {
+        return this.alternative && aborts(this.body) && aborts(this.alternative) && this;
+    });
+})(function(node, func) {
+    node.DEFMETHOD("aborts", func);
+});
+
+AST_Node.DEFMETHOD("contains_this", function() {
+    return walk(this, node => {
+        if (node instanceof AST_This) return walk_abort;
+        if (
+            node !== this
+            && node instanceof AST_Scope
+            && !(node instanceof AST_Arrow)
+        ) {
+            return true;
+        }
+    });
+});
+
+export function is_modified(compressor, tw, node, value, level, immutable) {
+    var parent = tw.parent(level);
+    var lhs = is_lhs(node, parent);
+    if (lhs) return lhs;
+    if (!immutable
+        && parent instanceof AST_Call
+        && parent.expression === node
+        && !(value instanceof AST_Arrow)
+        && !(value instanceof AST_Class)
+        && !parent.is_callee_pure(compressor)
+        && (!(value instanceof AST_Function)
+            || !(parent instanceof AST_New) && value.contains_this())) {
+        return true;
+    }
+    if (parent instanceof AST_Array) {
+        return is_modified(compressor, tw, parent, parent, level + 1);
+    }
+    if (parent instanceof AST_ObjectKeyVal && node === parent.value) {
+        var obj = tw.parent(level + 1);
+        return is_modified(compressor, tw, obj, obj, level + 2);
+    }
+    if (parent instanceof AST_PropAccess && parent.expression === node) {
+        var prop = read_property(value, parent.property);
+        return !immutable && is_modified(compressor, tw, parent, prop, level + 1);
+    }
+}

my-app/node_modules/terser/lib/compress/inline.js

@@ -0,0 +1,665 @@
+/***********************************************************************
+
+  A JavaScript tokenizer / parser / beautifier / compressor.
+  https://github.com/mishoo/UglifyJS2
+
+  -------------------------------- (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.
+
+ ***********************************************************************/
+
+import {
+    AST_Array,
+    AST_Assign,
+    AST_Block,
+    AST_Call,
+    AST_Catch,
+    AST_Class,
+    AST_ClassExpression,
+    AST_DefaultAssign,
+    AST_DefClass,
+    AST_Defun,
+    AST_Destructuring,
+    AST_EmptyStatement,
+    AST_Expansion,
+    AST_Export,
+    AST_Function,
+    AST_IterationStatement,
+    AST_Lambda,
+    AST_Node,
+    AST_Number,
+    AST_Object,
+    AST_ObjectKeyVal,
+    AST_PropAccess,
+    AST_Return,
+    AST_Scope,
+    AST_SimpleStatement,
+    AST_Statement,
+    AST_SymbolDefun,
+    AST_SymbolFunarg,
+    AST_SymbolLambda,
+    AST_SymbolRef,
+    AST_SymbolVar,
+    AST_This,
+    AST_Toplevel,
+    AST_UnaryPrefix,
+    AST_Undefined,
+    AST_Var,
+    AST_VarDef,
+
+    walk,
+
+    _INLINE,
+    _NOINLINE,
+    _PURE,
+} from "../ast.js";
+import { make_node, has_annotation } from "../utils/index.js";
+import "../size.js";
+
+import "./evaluate.js";
+import "./drop-side-effect-free.js";
+import "./reduce-vars.js";
+import {
+    SQUEEZED,
+    INLINED,
+    UNUSED,
+
+    has_flag,
+    set_flag,
+} from "./compressor-flags.js";
+import {
+    make_sequence,
+    best_of,
+    make_node_from_constant,
+    identifier_atom,
+    is_empty,
+    is_func_expr,
+    is_iife_call,
+    is_reachable,
+    is_recursive_ref,
+    retain_top_func,
+} from "./common.js";
+
+/**
+ * Module that contains the inlining logic.
+ *
+ * @module
+ *
+ * The stars of the show are `inline_into_symbolref` and `inline_into_call`.
+ */
+
+function within_array_or_object_literal(compressor) {
+    var node, level = 0;
+    while (node = compressor.parent(level++)) {
+        if (node instanceof AST_Statement) return false;
+        if (node instanceof AST_Array
+            || node instanceof AST_ObjectKeyVal
+            || node instanceof AST_Object) {
+            return true;
+        }
+    }
+    return false;
+}
+
+function scope_encloses_variables_in_this_scope(scope, pulled_scope) {
+    for (const enclosed of pulled_scope.enclosed) {
+        if (pulled_scope.variables.has(enclosed.name)) {
+            continue;
+        }
+        const looked_up = scope.find_variable(enclosed.name);
+        if (looked_up) {
+            if (looked_up === enclosed) continue;
+            return true;
+        }
+    }
+    return false;
+}
+
+/**
+ * An extra check function for `top_retain` option, compare the length of const identifier
+ * and init value length and return true if init value is longer than identifier. for example:
+ * ```
+ * // top_retain: ["example"]
+ * const example = 100
+ * ```
+ * it will return false because length of "100" is short than identifier "example".
+ */
+function is_const_symbol_short_than_init_value(def, fixed_value) {
+    if (def.orig.length === 1 && fixed_value) {
+        const init_value_length = fixed_value.size();
+        const identifer_length = def.name.length;
+        return init_value_length > identifer_length;
+    }
+    return true;
+}
+
+export function inline_into_symbolref(self, compressor) {
+    const parent = compressor.parent();
+    const def = self.definition();
+    const nearest_scope = compressor.find_scope();
+    let fixed = self.fixed_value();
+    if (
+        compressor.top_retain &&
+        def.global && 
+        compressor.top_retain(def) && 
+        // when identifier is in top_retain option dose not mean we can always inline it.
+        // if identifier name is longer then init value, we can replace it.
+        is_const_symbol_short_than_init_value(def, fixed)
+    ) {
+        // keep it
+        def.fixed = false;
+        def.single_use = false;
+        return self;
+    }
+
+    let single_use = def.single_use
+        && !(parent instanceof AST_Call
+            && (parent.is_callee_pure(compressor))
+                || has_annotation(parent, _NOINLINE))
+        && !(parent instanceof AST_Export
+            && fixed instanceof AST_Lambda
+            && fixed.name);
+
+    if (single_use && fixed instanceof AST_Node) {
+        single_use =
+            !fixed.has_side_effects(compressor)
+            && !fixed.may_throw(compressor);
+    }
+
+    if (fixed instanceof AST_Class && def.scope !== self.scope) {
+        return self;
+    }
+
+    if (single_use && (fixed instanceof AST_Lambda || fixed instanceof AST_Class)) {
+        if (retain_top_func(fixed, compressor)) {
+            single_use = false;
+        } else if (def.scope !== self.scope
+            && (def.escaped == 1
+                || has_flag(fixed, INLINED)
+                || within_array_or_object_literal(compressor)
+                || !compressor.option("reduce_funcs"))) {
+            single_use = false;
+        } else if (is_recursive_ref(compressor, def)) {
+            single_use = false;
+        } else if (def.scope !== self.scope || def.orig[0] instanceof AST_SymbolFunarg) {
+            single_use = fixed.is_constant_expression(self.scope);
+            if (single_use == "f") {
+                var scope = self.scope;
+                do {
+                    if (scope instanceof AST_Defun || is_func_expr(scope)) {
+                        set_flag(scope, INLINED);
+                    }
+                } while (scope = scope.parent_scope);
+            }
+        }
+    }
+
+    if (single_use && (fixed instanceof AST_Lambda || fixed instanceof AST_Class)) {
+        single_use =
+            def.scope === self.scope
+                && !scope_encloses_variables_in_this_scope(nearest_scope, fixed)
+            || parent instanceof AST_Call
+                && parent.expression === self
+                && !scope_encloses_variables_in_this_scope(nearest_scope, fixed)
+                && !(fixed.name && fixed.name.definition().recursive_refs > 0);
+    }
+
+    if (single_use && fixed) {
+        if (fixed instanceof AST_DefClass) {
+            set_flag(fixed, SQUEEZED);
+            fixed = make_node(AST_ClassExpression, fixed, fixed);
+        }
+        if (fixed instanceof AST_Defun) {
+            set_flag(fixed, SQUEEZED);
+            fixed = make_node(AST_Function, fixed, fixed);
+        }
+        if (def.recursive_refs > 0 && fixed.name instanceof AST_SymbolDefun) {
+            const defun_def = fixed.name.definition();
+            let lambda_def = fixed.variables.get(fixed.name.name);
+            let name = lambda_def && lambda_def.orig[0];
+            if (!(name instanceof AST_SymbolLambda)) {
+                name = make_node(AST_SymbolLambda, fixed.name, fixed.name);
+                name.scope = fixed;
+                fixed.name = name;
+                lambda_def = fixed.def_function(name);
+            }
+            walk(fixed, node => {
+                if (node instanceof AST_SymbolRef && node.definition() === defun_def) {
+                    node.thedef = lambda_def;
+                    lambda_def.references.push(node);
+                }
+            });
+        }
+        if (
+            (fixed instanceof AST_Lambda || fixed instanceof AST_Class)
+            && fixed.parent_scope !== nearest_scope
+        ) {
+            fixed = fixed.clone(true, compressor.get_toplevel());
+
+            nearest_scope.add_child_scope(fixed);
+        }
+        return fixed.optimize(compressor);
+    }
+
+    // multiple uses
+    if (fixed) {
+        let replace;
+
+        if (fixed instanceof AST_This) {
+            if (!(def.orig[0] instanceof AST_SymbolFunarg)
+                && def.references.every((ref) =>
+                    def.scope === ref.scope
+                )) {
+                replace = fixed;
+            }
+        } else {
+            var ev = fixed.evaluate(compressor);
+            if (
+                ev !== fixed
+                && (compressor.option("unsafe_regexp") || !(ev instanceof RegExp))
+            ) {
+                replace = make_node_from_constant(ev, fixed);
+            }
+        }
+
+        if (replace) {
+            const name_length = self.size(compressor);
+            const replace_size = replace.size(compressor);
+
+            let overhead = 0;
+            if (compressor.option("unused") && !compressor.exposed(def)) {
+                overhead =
+                    (name_length + 2 + replace_size) /
+                    (def.references.length - def.assignments);
+            }
+
+            if (replace_size <= name_length + overhead) {
+                return replace;
+            }
+        }
+    }
+
+    return self;
+}
+
+export function inline_into_call(self, compressor) {
+    var exp = self.expression;
+    var fn = exp;
+    var simple_args = self.args.every((arg) => !(arg instanceof AST_Expansion));
+
+    if (compressor.option("reduce_vars")
+        && fn instanceof AST_SymbolRef
+        && !has_annotation(self, _NOINLINE)
+    ) {
+        const fixed = fn.fixed_value();
+
+        if (
+            retain_top_func(fixed, compressor)
+            || !compressor.toplevel.funcs && exp.definition().global
+        ) {
+            return self;
+        }
+
+        fn = fixed;
+    }
+
+    var is_func = fn instanceof AST_Lambda;
+
+    var stat = is_func && fn.body[0];
+    var is_regular_func = is_func && !fn.is_generator && !fn.async;
+    var can_inline = is_regular_func && compressor.option("inline") && !self.is_callee_pure(compressor);
+    if (can_inline && stat instanceof AST_Return) {
+        let returned = stat.value;
+        if (!returned || returned.is_constant_expression()) {
+            if (returned) {
+                returned = returned.clone(true);
+            } else {
+                returned = make_node(AST_Undefined, self);
+            }
+            const args = self.args.concat(returned);
+            return make_sequence(self, args).optimize(compressor);
+        }
+
+        // optimize identity function
+        if (
+            fn.argnames.length === 1
+            && (fn.argnames[0] instanceof AST_SymbolFunarg)
+            && self.args.length < 2
+            && !(self.args[0] instanceof AST_Expansion)
+            && returned instanceof AST_SymbolRef
+            && returned.name === fn.argnames[0].name
+        ) {
+            const replacement =
+                (self.args[0] || make_node(AST_Undefined)).optimize(compressor);
+
+            let parent;
+            if (
+                replacement instanceof AST_PropAccess
+                && (parent = compressor.parent()) instanceof AST_Call
+                && parent.expression === self
+            ) {
+                // identity function was being used to remove `this`, like in
+                //
+                // id(bag.no_this)(...)
+                //
+                // Replace with a larger but more effish (0, bag.no_this) wrapper.
+
+                return make_sequence(self, [
+                    make_node(AST_Number, self, { value: 0 }),
+                    replacement
+                ]);
+            }
+            // replace call with first argument or undefined if none passed
+            return replacement;
+        }
+    }
+
+    if (can_inline) {
+        var scope, in_loop, level = -1;
+        let def;
+        let returned_value;
+        let nearest_scope;
+        if (simple_args
+            && !fn.uses_arguments
+            && !(compressor.parent() instanceof AST_Class)
+            && !(fn.name && fn instanceof AST_Function)
+            && (returned_value = can_flatten_body(stat))
+            && (exp === fn
+                || has_annotation(self, _INLINE)
+                || compressor.option("unused")
+                    && (def = exp.definition()).references.length == 1
+                    && !is_recursive_ref(compressor, def)
+                    && fn.is_constant_expression(exp.scope))
+            && !has_annotation(self, _PURE | _NOINLINE)
+            && !fn.contains_this()
+            && can_inject_symbols()
+            && (nearest_scope = compressor.find_scope())
+            && !scope_encloses_variables_in_this_scope(nearest_scope, fn)
+            && !(function in_default_assign() {
+                    // Due to the fact function parameters have their own scope
+                    // which can't use `var something` in the function body within,
+                    // we simply don't inline into DefaultAssign.
+                    let i = 0;
+                    let p;
+                    while ((p = compressor.parent(i++))) {
+                        if (p instanceof AST_DefaultAssign) return true;
+                        if (p instanceof AST_Block) break;
+                    }
+                    return false;
+                })()
+            && !(scope instanceof AST_Class)
+        ) {
+            set_flag(fn, SQUEEZED);
+            nearest_scope.add_child_scope(fn);
+            return make_sequence(self, flatten_fn(returned_value)).optimize(compressor);
+        }
+    }
+
+    if (can_inline && has_annotation(self, _INLINE)) {
+        set_flag(fn, SQUEEZED);
+        fn = make_node(fn.CTOR === AST_Defun ? AST_Function : fn.CTOR, fn, fn);
+        fn = fn.clone(true);
+        fn.figure_out_scope({}, {
+            parent_scope: compressor.find_scope(),
+            toplevel: compressor.get_toplevel()
+        });
+
+        return make_node(AST_Call, self, {
+            expression: fn,
+            args: self.args,
+        }).optimize(compressor);
+    }
+
+    const can_drop_this_call = is_regular_func && compressor.option("side_effects") && fn.body.every(is_empty);
+    if (can_drop_this_call) {
+        var args = self.args.concat(make_node(AST_Undefined, self));
+        return make_sequence(self, args).optimize(compressor);
+    }
+
+    if (compressor.option("negate_iife")
+        && compressor.parent() instanceof AST_SimpleStatement
+        && is_iife_call(self)) {
+        return self.negate(compressor, true);
+    }
+
+    var ev = self.evaluate(compressor);
+    if (ev !== self) {
+        ev = make_node_from_constant(ev, self).optimize(compressor);
+        return best_of(compressor, ev, self);
+    }
+
+    return self;
+
+    function return_value(stat) {
+        if (!stat) return make_node(AST_Undefined, self);
+        if (stat instanceof AST_Return) {
+            if (!stat.value) return make_node(AST_Undefined, self);
+            return stat.value.clone(true);
+        }
+        if (stat instanceof AST_SimpleStatement) {
+            return make_node(AST_UnaryPrefix, stat, {
+                operator: "void",
+                expression: stat.body.clone(true)
+            });
+        }
+    }
+
+    function can_flatten_body(stat) {
+        var body = fn.body;
+        var len = body.length;
+        if (compressor.option("inline") < 3) {
+            return len == 1 && return_value(stat);
+        }
+        stat = null;
+        for (var i = 0; i < len; i++) {
+            var line = body[i];
+            if (line instanceof AST_Var) {
+                if (stat && !line.definitions.every((var_def) =>
+                    !var_def.value
+                )) {
+                    return false;
+                }
+            } else if (stat) {
+                return false;
+            } else if (!(line instanceof AST_EmptyStatement)) {
+                stat = line;
+            }
+        }
+        return return_value(stat);
+    }
+
+    function can_inject_args(block_scoped, safe_to_inject) {
+        for (var i = 0, len = fn.argnames.length; i < len; i++) {
+            var arg = fn.argnames[i];
+            if (arg instanceof AST_DefaultAssign) {
+                if (has_flag(arg.left, UNUSED)) continue;
+                return false;
+            }
+            if (arg instanceof AST_Destructuring) return false;
+            if (arg instanceof AST_Expansion) {
+                if (has_flag(arg.expression, UNUSED)) continue;
+                return false;
+            }
+            if (has_flag(arg, UNUSED)) continue;
+            if (!safe_to_inject
+                || block_scoped.has(arg.name)
+                || identifier_atom.has(arg.name)
+                || scope.conflicting_def(arg.name)) {
+                return false;
+            }
+            if (in_loop) in_loop.push(arg.definition());
+        }
+        return true;
+    }
+
+    function can_inject_vars(block_scoped, safe_to_inject) {
+        var len = fn.body.length;
+        for (var i = 0; i < len; i++) {
+            var stat = fn.body[i];
+            if (!(stat instanceof AST_Var)) continue;
+            if (!safe_to_inject) return false;
+            for (var j = stat.definitions.length; --j >= 0;) {
+                var name = stat.definitions[j].name;
+                if (name instanceof AST_Destructuring
+                    || block_scoped.has(name.name)
+                    || identifier_atom.has(name.name)
+                    || scope.conflicting_def(name.name)) {
+                    return false;
+                }
+                if (in_loop) in_loop.push(name.definition());
+            }
+        }
+        return true;
+    }
+
+    function can_inject_symbols() {
+        var block_scoped = new Set();
+        do {
+            scope = compressor.parent(++level);
+            if (scope.is_block_scope() && scope.block_scope) {
+                // TODO this is sometimes undefined during compression.
+                // But it should always have a value!
+                scope.block_scope.variables.forEach(function (variable) {
+                    block_scoped.add(variable.name);
+                });
+            }
+            if (scope instanceof AST_Catch) {
+                // TODO can we delete? AST_Catch is a block scope.
+                if (scope.argname) {
+                    block_scoped.add(scope.argname.name);
+                }
+            } else if (scope instanceof AST_IterationStatement) {
+                in_loop = [];
+            } else if (scope instanceof AST_SymbolRef) {
+                if (scope.fixed_value() instanceof AST_Scope) return false;
+            }
+        } while (!(scope instanceof AST_Scope));
+
+        var safe_to_inject = !(scope instanceof AST_Toplevel) || compressor.toplevel.vars;
+        var inline = compressor.option("inline");
+        if (!can_inject_vars(block_scoped, inline >= 3 && safe_to_inject)) return false;
+        if (!can_inject_args(block_scoped, inline >= 2 && safe_to_inject)) return false;
+        return !in_loop || in_loop.length == 0 || !is_reachable(fn, in_loop);
+    }
+
+    function append_var(decls, expressions, name, value) {
+        var def = name.definition();
+
+        // Name already exists, only when a function argument had the same name
+        const already_appended = scope.variables.has(name.name);
+        if (!already_appended) {
+            scope.variables.set(name.name, def);
+            scope.enclosed.push(def);
+            decls.push(make_node(AST_VarDef, name, {
+                name: name,
+                value: null
+            }));
+        }
+
+        var sym = make_node(AST_SymbolRef, name, name);
+        def.references.push(sym);
+        if (value) expressions.push(make_node(AST_Assign, self, {
+            operator: "=",
+            logical: false,
+            left: sym,
+            right: value.clone()
+        }));
+    }
+
+    function flatten_args(decls, expressions) {
+        var len = fn.argnames.length;
+        for (var i = self.args.length; --i >= len;) {
+            expressions.push(self.args[i]);
+        }
+        for (i = len; --i >= 0;) {
+            var name = fn.argnames[i];
+            var value = self.args[i];
+            if (has_flag(name, UNUSED) || !name.name || scope.conflicting_def(name.name)) {
+                if (value) expressions.push(value);
+            } else {
+                var symbol = make_node(AST_SymbolVar, name, name);
+                name.definition().orig.push(symbol);
+                if (!value && in_loop) value = make_node(AST_Undefined, self);
+                append_var(decls, expressions, symbol, value);
+            }
+        }
+        decls.reverse();
+        expressions.reverse();
+    }
+
+    function flatten_vars(decls, expressions) {
+        var pos = expressions.length;
+        for (var i = 0, lines = fn.body.length; i < lines; i++) {
+            var stat = fn.body[i];
+            if (!(stat instanceof AST_Var)) continue;
+            for (var j = 0, defs = stat.definitions.length; j < defs; j++) {
+                var var_def = stat.definitions[j];
+                var name = var_def.name;
+                append_var(decls, expressions, name, var_def.value);
+                if (in_loop && fn.argnames.every((argname) =>
+                    argname.name != name.name
+                )) {
+                    var def = fn.variables.get(name.name);
+                    var sym = make_node(AST_SymbolRef, name, name);
+                    def.references.push(sym);
+                    expressions.splice(pos++, 0, make_node(AST_Assign, var_def, {
+                        operator: "=",
+                        logical: false,
+                        left: sym,
+                        right: make_node(AST_Undefined, name)
+                    }));
+                }
+            }
+        }
+    }
+
+    function flatten_fn(returned_value) {
+        var decls = [];
+        var expressions = [];
+        flatten_args(decls, expressions);
+        flatten_vars(decls, expressions);
+        expressions.push(returned_value);
+
+        if (decls.length) {
+            const i = scope.body.indexOf(compressor.parent(level - 1)) + 1;
+            scope.body.splice(i, 0, make_node(AST_Var, fn, {
+                definitions: decls
+            }));
+        }
+
+        return expressions.map(exp => exp.clone(true));
+    }
+}

my-app/node_modules/terser/lib/compress/native-objects.js

@@ -0,0 +1,206 @@
+/***********************************************************************
+
+  A JavaScript tokenizer / parser / beautifier / compressor.
+  https://github.com/mishoo/UglifyJS2
+
+  -------------------------------- (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.
+
+ ***********************************************************************/
+
+import { makePredicate } from "../utils/index.js";
+
+// Lists of native methods, useful for `unsafe` option which assumes they exist.
+// Note: Lots of methods and functions are missing here, in case they aren't pure
+// or not available in all JS environments.
+
+function make_nested_lookup(obj) {
+    const out = new Map();
+    for (var key of Object.keys(obj)) {
+        out.set(key, makePredicate(obj[key]));
+    }
+
+    const does_have = (global_name, fname) => {
+        const inner_map = out.get(global_name);
+        return inner_map != null && inner_map.has(fname);
+    };
+    return does_have;
+}
+
+// Objects which are safe to access without throwing or causing a side effect.
+// Usually we'd check the `unsafe` option first but these are way too common for that
+export const pure_prop_access_globals = new Set([
+    "Number",
+    "String",
+    "Array",
+    "Object",
+    "Function",
+    "Promise",
+]);
+
+const object_methods = [
+    "constructor",
+    "toString",
+    "valueOf",
+];
+
+export const is_pure_native_method = make_nested_lookup({
+    Array: [
+        "at",
+        "flat",
+        "includes",
+        "indexOf",
+        "join",
+        "lastIndexOf",
+        "slice",
+        ...object_methods,
+    ],
+    Boolean: object_methods,
+    Function: object_methods,
+    Number: [
+        "toExponential",
+        "toFixed",
+        "toPrecision",
+        ...object_methods,
+    ],
+    Object: object_methods,
+    RegExp: [
+        "test",
+        ...object_methods,
+    ],
+    String: [
+        "at",
+        "charAt",
+        "charCodeAt",
+        "charPointAt",
+        "concat",
+        "endsWith",
+        "fromCharCode",
+        "fromCodePoint",
+        "includes",
+        "indexOf",
+        "italics",
+        "lastIndexOf",
+        "localeCompare",
+        "match",
+        "matchAll",
+        "normalize",
+        "padStart",
+        "padEnd",
+        "repeat",
+        "replace",
+        "replaceAll",
+        "search",
+        "slice",
+        "split",
+        "startsWith",
+        "substr",
+        "substring",
+        "repeat",
+        "toLocaleLowerCase",
+        "toLocaleUpperCase",
+        "toLowerCase",
+        "toUpperCase",
+        "trim",
+        "trimEnd",
+        "trimStart",
+        ...object_methods,
+    ],
+});
+
+export const is_pure_native_fn = make_nested_lookup({
+    Array: [
+        "isArray",
+    ],
+    Math: [
+        "abs",
+        "acos",
+        "asin",
+        "atan",
+        "ceil",
+        "cos",
+        "exp",
+        "floor",
+        "log",
+        "round",
+        "sin",
+        "sqrt",
+        "tan",
+        "atan2",
+        "pow",
+        "max",
+        "min",
+    ],
+    Number: [
+        "isFinite",
+        "isNaN",
+    ],
+    Object: [
+        "create",
+        "getOwnPropertyDescriptor",
+        "getOwnPropertyNames",
+        "getPrototypeOf",
+        "isExtensible",
+        "isFrozen",
+        "isSealed",
+        "hasOwn",
+        "keys",
+    ],
+    String: [
+        "fromCharCode",
+    ],
+});
+
+// Known numeric values which come with JS environments
+export const is_pure_native_value = make_nested_lookup({
+    Math: [
+        "E",
+        "LN10",
+        "LN2",
+        "LOG2E",
+        "LOG10E",
+        "PI",
+        "SQRT1_2",
+        "SQRT2",
+    ],
+    Number: [
+        "MAX_VALUE",
+        "MIN_VALUE",
+        "NaN",
+        "NEGATIVE_INFINITY",
+        "POSITIVE_INFINITY",
+    ],
+});

my-app/node_modules/terser/lib/compress/reduce-vars.js

@@ -0,0 +1,824 @@
+/***********************************************************************
+
+  A JavaScript tokenizer / parser / beautifier / compressor.
+  https://github.com/mishoo/UglifyJS2
+
+  -------------------------------- (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.
+
+ ***********************************************************************/
+
+import {
+    AST_Accessor,
+    AST_Array,
+    AST_Assign,
+    AST_Await,
+    AST_Binary,
+    AST_Block,
+    AST_Call,
+    AST_Case,
+    AST_Chain,
+    AST_Class,
+    AST_ClassStaticBlock,
+    AST_ClassExpression,
+    AST_Conditional,
+    AST_Default,
+    AST_Defun,
+    AST_Destructuring,
+    AST_Do,
+    AST_Exit,
+    AST_Expansion,
+    AST_For,
+    AST_ForIn,
+    AST_If,
+    AST_LabeledStatement,
+    AST_Lambda,
+    AST_New,
+    AST_Node,
+    AST_Number,
+    AST_ObjectKeyVal,
+    AST_PropAccess,
+    AST_Scope,
+    AST_Sequence,
+    AST_SimpleStatement,
+    AST_Symbol,
+    AST_SymbolCatch,
+    AST_SymbolConst,
+    AST_SymbolDeclaration,
+    AST_SymbolDefun,
+    AST_SymbolFunarg,
+    AST_SymbolLambda,
+    AST_SymbolRef,
+    AST_This,
+    AST_Toplevel,
+    AST_Try,
+    AST_Unary,
+    AST_UnaryPrefix,
+    AST_Undefined,
+    AST_VarDef,
+    AST_While,
+    AST_Yield,
+
+    walk,
+    walk_body,
+
+    TreeWalker,
+} from "../ast.js";
+import { HOP, make_node, noop } from "../utils/index.js";
+
+import { lazy_op, is_modified, is_lhs } from "./inference.js";
+import { INLINED, clear_flag } from "./compressor-flags.js";
+import { read_property, has_break_or_continue, is_recursive_ref } from "./common.js";
+
+/**
+ * Define the method AST_Node#reduce_vars, which goes through the AST in
+ * execution order to perform basic flow analysis
+ */
+function def_reduce_vars(node, func) {
+    node.DEFMETHOD("reduce_vars", func);
+}
+
+def_reduce_vars(AST_Node, noop);
+
+/** Clear definition properties */
+function reset_def(compressor, def) {
+    def.assignments = 0;
+    def.chained = false;
+    def.direct_access = false;
+    def.escaped = 0;
+    def.recursive_refs = 0;
+    def.references = [];
+    def.single_use = undefined;
+    if (
+        def.scope.pinned()
+        || (def.orig[0] instanceof AST_SymbolFunarg && def.scope.uses_arguments)
+    ) {
+        def.fixed = false;
+    } else if (def.orig[0] instanceof AST_SymbolConst || !compressor.exposed(def)) {
+        def.fixed = def.init;
+    } else {
+        def.fixed = false;
+    }
+}
+
+function reset_variables(tw, compressor, node) {
+    node.variables.forEach(function(def) {
+        reset_def(compressor, def);
+        if (def.fixed === null) {
+            tw.defs_to_safe_ids.set(def.id, tw.safe_ids);
+            mark(tw, def, true);
+        } else if (def.fixed) {
+            tw.loop_ids.set(def.id, tw.in_loop);
+            mark(tw, def, true);
+        }
+    });
+}
+
+function reset_block_variables(compressor, node) {
+    if (node.block_scope) node.block_scope.variables.forEach((def) => {
+        reset_def(compressor, def);
+    });
+}
+
+function push(tw) {
+    tw.safe_ids = Object.create(tw.safe_ids);
+}
+
+function pop(tw) {
+    tw.safe_ids = Object.getPrototypeOf(tw.safe_ids);
+}
+
+function mark(tw, def, safe) {
+    tw.safe_ids[def.id] = safe;
+}
+
+function safe_to_read(tw, def) {
+    if (def.single_use == "m") return false;
+    if (tw.safe_ids[def.id]) {
+        if (def.fixed == null) {
+            var orig = def.orig[0];
+            if (orig instanceof AST_SymbolFunarg || orig.name == "arguments") return false;
+            def.fixed = make_node(AST_Undefined, orig);
+        }
+        return true;
+    }
+    return def.fixed instanceof AST_Defun;
+}
+
+function safe_to_assign(tw, def, scope, value) {
+    if (def.fixed === undefined) return true;
+    let def_safe_ids;
+    if (def.fixed === null
+        && (def_safe_ids = tw.defs_to_safe_ids.get(def.id))
+    ) {
+        def_safe_ids[def.id] = false;
+        tw.defs_to_safe_ids.delete(def.id);
+        return true;
+    }
+    if (!HOP(tw.safe_ids, def.id)) return false;
+    if (!safe_to_read(tw, def)) return false;
+    if (def.fixed === false) return false;
+    if (def.fixed != null && (!value || def.references.length > def.assignments)) return false;
+    if (def.fixed instanceof AST_Defun) {
+        return value instanceof AST_Node && def.fixed.parent_scope === scope;
+    }
+    return def.orig.every((sym) => {
+        return !(sym instanceof AST_SymbolConst
+            || sym instanceof AST_SymbolDefun
+            || sym instanceof AST_SymbolLambda);
+    });
+}
+
+function ref_once(tw, compressor, def) {
+    return compressor.option("unused")
+        && !def.scope.pinned()
+        && def.references.length - def.recursive_refs == 1
+        && tw.loop_ids.get(def.id) === tw.in_loop;
+}
+
+function is_immutable(value) {
+    if (!value) return false;
+    return value.is_constant()
+        || value instanceof AST_Lambda
+        || value instanceof AST_This;
+}
+
+// A definition "escapes" when its value can leave the point of use.
+// Example: `a = b || c`
+// In this example, "b" and "c" are escaping, because they're going into "a"
+//
+// def.escaped is != 0 when it escapes.
+//
+// When greater than 1, it means that N chained properties will be read off
+// of that def before an escape occurs. This is useful for evaluating
+// property accesses, where you need to know when to stop.
+function mark_escaped(tw, d, scope, node, value, level = 0, depth = 1) {
+    var parent = tw.parent(level);
+    if (value) {
+        if (value.is_constant()) return;
+        if (value instanceof AST_ClassExpression) return;
+    }
+
+    if (
+        parent instanceof AST_Assign && (parent.operator === "=" || parent.logical) && node === parent.right
+        || parent instanceof AST_Call && (node !== parent.expression || parent instanceof AST_New)
+        || parent instanceof AST_Exit && node === parent.value && node.scope !== d.scope
+        || parent instanceof AST_VarDef && node === parent.value
+        || parent instanceof AST_Yield && node === parent.value && node.scope !== d.scope
+    ) {
+        if (depth > 1 && !(value && value.is_constant_expression(scope))) depth = 1;
+        if (!d.escaped || d.escaped > depth) d.escaped = depth;
+        return;
+    } else if (
+        parent instanceof AST_Array
+        || parent instanceof AST_Await
+        || parent instanceof AST_Binary && lazy_op.has(parent.operator)
+        || parent instanceof AST_Conditional && node !== parent.condition
+        || parent instanceof AST_Expansion
+        || parent instanceof AST_Sequence && node === parent.tail_node()
+    ) {
+        mark_escaped(tw, d, scope, parent, parent, level + 1, depth);
+    } else if (parent instanceof AST_ObjectKeyVal && node === parent.value) {
+        var obj = tw.parent(level + 1);
+
+        mark_escaped(tw, d, scope, obj, obj, level + 2, depth);
+    } else if (parent instanceof AST_PropAccess && node === parent.expression) {
+        value = read_property(value, parent.property);
+
+        mark_escaped(tw, d, scope, parent, value, level + 1, depth + 1);
+        if (value) return;
+    }
+
+    if (level > 0) return;
+    if (parent instanceof AST_Sequence && node !== parent.tail_node()) return;
+    if (parent instanceof AST_SimpleStatement) return;
+
+    d.direct_access = true;
+}
+
+const suppress = node => walk(node, node => {
+    if (!(node instanceof AST_Symbol)) return;
+    var d = node.definition();
+    if (!d) return;
+    if (node instanceof AST_SymbolRef) d.references.push(node);
+    d.fixed = false;
+});
+
+def_reduce_vars(AST_Accessor, function(tw, descend, compressor) {
+    push(tw);
+    reset_variables(tw, compressor, this);
+    descend();
+    pop(tw);
+    return true;
+});
+
+def_reduce_vars(AST_Assign, function(tw, descend, compressor) {
+    var node = this;
+    if (node.left instanceof AST_Destructuring) {
+        suppress(node.left);
+        return;
+    }
+
+    const finish_walk = () => {
+        if (node.logical) {
+            node.left.walk(tw);
+
+            push(tw);
+            node.right.walk(tw);
+            pop(tw);
+
+            return true;
+        }
+    };
+
+    var sym = node.left;
+    if (!(sym instanceof AST_SymbolRef)) return finish_walk();
+
+    var def = sym.definition();
+    var safe = safe_to_assign(tw, def, sym.scope, node.right);
+    def.assignments++;
+    if (!safe) return finish_walk();
+
+    var fixed = def.fixed;
+    if (!fixed && node.operator != "=" && !node.logical) return finish_walk();
+
+    var eq = node.operator == "=";
+    var value = eq ? node.right : node;
+    if (is_modified(compressor, tw, node, value, 0)) return finish_walk();
+
+    def.references.push(sym);
+
+    if (!node.logical) {
+        if (!eq) def.chained = true;
+
+        def.fixed = eq ? function() {
+            return node.right;
+        } : function() {
+            return make_node(AST_Binary, node, {
+                operator: node.operator.slice(0, -1),
+                left: fixed instanceof AST_Node ? fixed : fixed(),
+                right: node.right
+            });
+        };
+    }
+
+    if (node.logical) {
+        mark(tw, def, false);
+        push(tw);
+        node.right.walk(tw);
+        pop(tw);
+        return true;
+    }
+
+    mark(tw, def, false);
+    node.right.walk(tw);
+    mark(tw, def, true);
+
+    mark_escaped(tw, def, sym.scope, node, value, 0, 1);
+
+    return true;
+});
+
+def_reduce_vars(AST_Binary, function(tw) {
+    if (!lazy_op.has(this.operator)) return;
+    this.left.walk(tw);
+    push(tw);
+    this.right.walk(tw);
+    pop(tw);
+    return true;
+});
+
+def_reduce_vars(AST_Block, function(tw, descend, compressor) {
+    reset_block_variables(compressor, this);
+});
+
+def_reduce_vars(AST_Case, function(tw) {
+    push(tw);
+    this.expression.walk(tw);
+    pop(tw);
+    push(tw);
+    walk_body(this, tw);
+    pop(tw);
+    return true;
+});
+
+def_reduce_vars(AST_Class, function(tw, descend) {
+    clear_flag(this, INLINED);
+    push(tw);
+    descend();
+    pop(tw);
+    return true;
+});
+
+def_reduce_vars(AST_ClassStaticBlock, function(tw, descend, compressor) {
+    reset_block_variables(compressor, this);
+});
+
+def_reduce_vars(AST_Conditional, function(tw) {
+    this.condition.walk(tw);
+    push(tw);
+    this.consequent.walk(tw);
+    pop(tw);
+    push(tw);
+    this.alternative.walk(tw);
+    pop(tw);
+    return true;
+});
+
+def_reduce_vars(AST_Chain, function(tw, descend) {
+    // Chains' conditions apply left-to-right, cumulatively.
+    // If we walk normally we don't go in that order because we would pop before pushing again
+    // Solution: AST_PropAccess and AST_Call push when they are optional, and never pop.
+    // Then we pop everything when they are done being walked.
+    const safe_ids = tw.safe_ids;
+
+    descend();
+
+    // Unroll back to start
+    tw.safe_ids = safe_ids;
+    return true;
+});
+
+def_reduce_vars(AST_Call, function (tw) {
+    this.expression.walk(tw);
+
+    if (this.optional) {
+        // Never pop -- it's popped at AST_Chain above
+        push(tw);
+    }
+
+    for (const arg of this.args) arg.walk(tw);
+
+    return true;
+});
+
+def_reduce_vars(AST_PropAccess, function (tw) {
+    if (!this.optional) return;
+
+    this.expression.walk(tw);
+
+    // Never pop -- it's popped at AST_Chain above
+    push(tw);
+
+    if (this.property instanceof AST_Node) this.property.walk(tw);
+
+    return true;
+});
+
+def_reduce_vars(AST_Default, function(tw, descend) {
+    push(tw);
+    descend();
+    pop(tw);
+    return true;
+});
+
+function mark_lambda(tw, descend, compressor) {
+    clear_flag(this, INLINED);
+    push(tw);
+    reset_variables(tw, compressor, this);
+
+    var iife;
+    if (!this.name
+        && !this.uses_arguments
+        && !this.pinned()
+        && (iife = tw.parent()) instanceof AST_Call
+        && iife.expression === this
+        && !iife.args.some(arg => arg instanceof AST_Expansion)
+        && this.argnames.every(arg_name => arg_name instanceof AST_Symbol)
+    ) {
+        // Virtually turn IIFE parameters into variable definitions:
+        //   (function(a,b) {...})(c,d) => (function() {var a=c,b=d; ...})()
+        // So existing transformation rules can work on them.
+        this.argnames.forEach((arg, i) => {
+            if (!arg.definition) return;
+            var d = arg.definition();
+            // Avoid setting fixed when there's more than one origin for a variable value
+            if (d.orig.length > 1) return;
+            if (d.fixed === undefined && (!this.uses_arguments || tw.has_directive("use strict"))) {
+                d.fixed = function() {
+                    return iife.args[i] || make_node(AST_Undefined, iife);
+                };
+                tw.loop_ids.set(d.id, tw.in_loop);
+                mark(tw, d, true);
+            } else {
+                d.fixed = false;
+            }
+        });
+    }
+
+    descend();
+    pop(tw);
+
+    handle_defined_after_hoist(this);
+
+    return true;
+}
+
+/**
+ * It's possible for a hoisted function to use something that's not defined yet. Example:
+ *
+ * hoisted();
+ * var defined_after = true;
+ * function hoisted() {
+ *   // use defined_after
+ * }
+ *
+ * This function is called on the parent to handle this issue.
+ */
+function handle_defined_after_hoist(parent) {
+    const defuns = [];
+    walk(parent, node => {
+        if (node === parent) return;
+        if (node instanceof AST_Defun) defuns.push(node);
+        if (
+            node instanceof AST_Scope
+            || node instanceof AST_SimpleStatement
+        ) return true;
+    });
+
+    const symbols_of_interest = new Set();
+    const defuns_of_interest = new Set();
+    const potential_conflicts = [];
+
+    for (const defun of defuns) {
+        const fname_def = defun.name.definition();
+        const found_self_ref_in_other_defuns = defuns.some(
+            d => d !== defun && d.enclosed.indexOf(fname_def) !== -1
+        );
+
+        for (const def of defun.enclosed) {
+            if (
+                def.fixed === false
+                || def === fname_def
+                || def.scope.get_defun_scope() !== parent
+            ) {
+                continue;
+            }
+
+            // defun is hoisted, so always safe
+            if (
+                def.assignments === 0
+                && def.orig.length === 1
+                && def.orig[0] instanceof AST_SymbolDefun
+            ) {
+                continue;
+            }
+
+            if (found_self_ref_in_other_defuns) {
+                def.fixed = false;
+                continue;
+            }
+
+            // for the slower checks below this loop
+            potential_conflicts.push({ defun, def, fname_def });
+            symbols_of_interest.add(def.id);
+            symbols_of_interest.add(fname_def.id);
+            defuns_of_interest.add(defun);
+        }
+    }
+
+    // linearize all symbols, and locate defs that are read after the defun
+    if (potential_conflicts.length) {
+        // All "symbols of interest", that is, defuns or defs, that we found.
+        // These are placed in order so we can check which is after which.
+        const found_symbols = [];
+        // Indices of `found_symbols` which are writes
+        const found_symbol_writes = new Set();
+        // Defun ranges are recorded because we don't care if a function uses the def internally
+        const defun_ranges = new Map();
+
+        let tw;
+        parent.walk((tw = new TreeWalker((node, descend) => {
+            if (node instanceof AST_Defun && defuns_of_interest.has(node)) {
+                const start = found_symbols.length;
+                descend();
+                const end = found_symbols.length;
+
+                defun_ranges.set(node, { start, end });
+                return true;
+            }
+            // if we found a defun on the list, mark IN_DEFUN=id and descend
+
+            if (node instanceof AST_Symbol && node.thedef) {
+                const id = node.definition().id;
+                if (symbols_of_interest.has(id)) {
+                    if (node instanceof AST_SymbolDeclaration || is_lhs(node, tw)) {
+                        found_symbol_writes.add(found_symbols.length);
+                    }
+                    found_symbols.push(id);
+                }
+            }
+        })));
+
+        for (const { def, defun, fname_def } of potential_conflicts) {
+            const defun_range = defun_ranges.get(defun);
+
+            // find the index in `found_symbols`, with some special rules:
+            const find = (sym_id, starting_at = 0, must_be_write = false) => {
+                let index = starting_at;
+
+                for (;;) {
+                    index = found_symbols.indexOf(sym_id, index);
+
+                    if (index === -1) {
+                        break;
+                    } else if (index >= defun_range.start && index < defun_range.end) {
+                        index = defun_range.end;
+                        continue;
+                    } else if (must_be_write && !found_symbol_writes.has(index)) {
+                        index++;
+                        continue;
+                    } else {
+                        break;
+                    }
+                }
+
+                return index;
+            };
+
+            const read_defun_at = find(fname_def.id);
+            const wrote_def_at = find(def.id, read_defun_at + 1, true);
+
+            const wrote_def_after_reading_defun = read_defun_at != -1 && wrote_def_at != -1 && wrote_def_at > read_defun_at;
+
+            if (wrote_def_after_reading_defun) {
+                def.fixed = false;
+            }
+        }
+    }
+}
+
+def_reduce_vars(AST_Lambda, mark_lambda);
+
+def_reduce_vars(AST_Do, function(tw, descend, compressor) {
+    reset_block_variables(compressor, this);
+    const saved_loop = tw.in_loop;
+    tw.in_loop = this;
+    push(tw);
+    this.body.walk(tw);
+    if (has_break_or_continue(this)) {
+        pop(tw);
+        push(tw);
+    }
+    this.condition.walk(tw);
+    pop(tw);
+    tw.in_loop = saved_loop;
+    return true;
+});
+
+def_reduce_vars(AST_For, function(tw, descend, compressor) {
+    reset_block_variables(compressor, this);
+    if (this.init) this.init.walk(tw);
+    const saved_loop = tw.in_loop;
+    tw.in_loop = this;
+    push(tw);
+    if (this.condition) this.condition.walk(tw);
+    this.body.walk(tw);
+    if (this.step) {
+        if (has_break_or_continue(this)) {
+            pop(tw);
+            push(tw);
+        }
+        this.step.walk(tw);
+    }
+    pop(tw);
+    tw.in_loop = saved_loop;
+    return true;
+});
+
+def_reduce_vars(AST_ForIn, function(tw, descend, compressor) {
+    reset_block_variables(compressor, this);
+    suppress(this.init);
+    this.object.walk(tw);
+    const saved_loop = tw.in_loop;
+    tw.in_loop = this;
+    push(tw);
+    this.body.walk(tw);
+    pop(tw);
+    tw.in_loop = saved_loop;
+    return true;
+});
+
+def_reduce_vars(AST_If, function(tw) {
+    this.condition.walk(tw);
+    push(tw);
+    this.body.walk(tw);
+    pop(tw);
+    if (this.alternative) {
+        push(tw);
+        this.alternative.walk(tw);
+        pop(tw);
+    }
+    return true;
+});
+
+def_reduce_vars(AST_LabeledStatement, function(tw) {
+    push(tw);
+    this.body.walk(tw);
+    pop(tw);
+    return true;
+});
+
+def_reduce_vars(AST_SymbolCatch, function() {
+    this.definition().fixed = false;
+});
+
+def_reduce_vars(AST_SymbolRef, function(tw, descend, compressor) {
+    var d = this.definition();
+    d.references.push(this);
+    if (d.references.length == 1
+        && !d.fixed
+        && d.orig[0] instanceof AST_SymbolDefun) {
+        tw.loop_ids.set(d.id, tw.in_loop);
+    }
+    var fixed_value;
+    if (d.fixed === undefined || !safe_to_read(tw, d)) {
+        d.fixed = false;
+    } else if (d.fixed) {
+        fixed_value = this.fixed_value();
+        if (
+            fixed_value instanceof AST_Lambda
+            && is_recursive_ref(tw, d)
+        ) {
+            d.recursive_refs++;
+        } else if (fixed_value
+            && !compressor.exposed(d)
+            && ref_once(tw, compressor, d)
+        ) {
+            d.single_use =
+                fixed_value instanceof AST_Lambda && !fixed_value.pinned()
+                || fixed_value instanceof AST_Class
+                || d.scope === this.scope && fixed_value.is_constant_expression();
+        } else {
+            d.single_use = false;
+        }
+        if (is_modified(compressor, tw, this, fixed_value, 0, is_immutable(fixed_value))) {
+            if (d.single_use) {
+                d.single_use = "m";
+            } else {
+                d.fixed = false;
+            }
+        }
+    }
+    mark_escaped(tw, d, this.scope, this, fixed_value, 0, 1);
+});
+
+def_reduce_vars(AST_Toplevel, function(tw, descend, compressor) {
+    this.globals.forEach(function(def) {
+        reset_def(compressor, def);
+    });
+    reset_variables(tw, compressor, this);
+    descend();
+    handle_defined_after_hoist(this);
+    return true;
+});
+
+def_reduce_vars(AST_Try, function(tw, descend, compressor) {
+    reset_block_variables(compressor, this);
+    push(tw);
+    this.body.walk(tw);
+    pop(tw);
+    if (this.bcatch) {
+        push(tw);
+        this.bcatch.walk(tw);
+        pop(tw);
+    }
+    if (this.bfinally) this.bfinally.walk(tw);
+    return true;
+});
+
+def_reduce_vars(AST_Unary, function(tw) {
+    var node = this;
+    if (node.operator !== "++" && node.operator !== "--") return;
+    var exp = node.expression;
+    if (!(exp instanceof AST_SymbolRef)) return;
+    var def = exp.definition();
+    var safe = safe_to_assign(tw, def, exp.scope, true);
+    def.assignments++;
+    if (!safe) return;
+    var fixed = def.fixed;
+    if (!fixed) return;
+    def.references.push(exp);
+    def.chained = true;
+    def.fixed = function() {
+        return make_node(AST_Binary, node, {
+            operator: node.operator.slice(0, -1),
+            left: make_node(AST_UnaryPrefix, node, {
+                operator: "+",
+                expression: fixed instanceof AST_Node ? fixed : fixed()
+            }),
+            right: make_node(AST_Number, node, {
+                value: 1
+            })
+        });
+    };
+    mark(tw, def, true);
+    return true;
+});
+
+def_reduce_vars(AST_VarDef, function(tw, descend) {
+    var node = this;
+    if (node.name instanceof AST_Destructuring) {
+        suppress(node.name);
+        return;
+    }
+    var d = node.name.definition();
+    if (node.value) {
+        if (safe_to_assign(tw, d, node.name.scope, node.value)) {
+            d.fixed = function() {
+                return node.value;
+            };
+            tw.loop_ids.set(d.id, tw.in_loop);
+            mark(tw, d, false);
+            descend();
+            mark(tw, d, true);
+            return true;
+        } else {
+            d.fixed = false;
+        }
+    }
+});
+
+def_reduce_vars(AST_While, function(tw, descend, compressor) {
+    reset_block_variables(compressor, this);
+    const saved_loop = tw.in_loop;
+    tw.in_loop = this;
+    push(tw);
+    descend();
+    pop(tw);
+    tw.in_loop = saved_loop;
+    return true;
+});