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360 lines
13 KiB
360 lines
13 KiB
/***********************************************************************
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A JavaScript tokenizer / parser / beautifier / compressor.
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https://github.com/mishoo/UglifyJS2
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-------------------------------- (C) ---------------------------------
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Author: Mihai Bazon
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<mihai.bazon@gmail.com>
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http://mihai.bazon.net/blog
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Distributed under the BSD license:
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Copyright 2012 (c) Mihai Bazon <mihai.bazon@gmail.com>
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions
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are met:
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* Redistributions of source code must retain the above
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copyright notice, this list of conditions and the following
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disclaimer.
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* Redistributions in binary form must reproduce the above
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copyright notice, this list of conditions and the following
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disclaimer in the documentation and/or other materials
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provided with the distribution.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER “AS IS” AND ANY
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EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER BE
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LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
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OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR
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TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
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THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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SUCH DAMAGE.
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***********************************************************************/
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import {
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AST_Accessor,
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AST_Array,
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AST_Arrow,
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AST_Assign,
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AST_Binary,
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AST_Call,
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AST_Chain,
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AST_Class,
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AST_ClassStaticBlock,
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AST_ClassProperty,
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AST_ConciseMethod,
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AST_Conditional,
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AST_Constant,
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AST_Dot,
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AST_Expansion,
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AST_Function,
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AST_Node,
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AST_Number,
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AST_Object,
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AST_ObjectGetter,
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AST_ObjectKeyVal,
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AST_ObjectProperty,
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AST_ObjectSetter,
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AST_PropAccess,
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AST_Scope,
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AST_Sequence,
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AST_Sub,
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AST_SymbolRef,
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AST_TemplateSegment,
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AST_TemplateString,
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AST_This,
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AST_Unary,
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} from "../ast.js";
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import { make_node, return_null, return_this } from "../utils/index.js";
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import { first_in_statement } from "../utils/first_in_statement.js";
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import { pure_prop_access_globals } from "./native-objects.js";
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import { lazy_op, unary_side_effects, is_nullish_shortcircuited } from "./inference.js";
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import { WRITE_ONLY, set_flag, clear_flag } from "./compressor-flags.js";
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import { make_sequence, is_func_expr, is_iife_call } from "./common.js";
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// AST_Node#drop_side_effect_free() gets called when we don't care about the value,
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// only about side effects. We'll be defining this method for each node type in this module
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//
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// Examples:
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// foo++ -> foo++
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// 1 + func() -> func()
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// 10 -> (nothing)
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// knownPureFunc(foo++) -> foo++
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function def_drop_side_effect_free(node, func) {
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node.DEFMETHOD("drop_side_effect_free", func);
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}
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// Drop side-effect-free elements from an array of expressions.
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// Returns an array of expressions with side-effects or null
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// if all elements were dropped. Note: original array may be
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// returned if nothing changed.
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function trim(nodes, compressor, first_in_statement) {
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var len = nodes.length;
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if (!len) return null;
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var ret = [], changed = false;
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for (var i = 0; i < len; i++) {
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var node = nodes[i].drop_side_effect_free(compressor, first_in_statement);
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changed |= node !== nodes[i];
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if (node) {
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ret.push(node);
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first_in_statement = false;
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}
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}
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return changed ? ret.length ? ret : null : nodes;
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}
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def_drop_side_effect_free(AST_Node, return_this);
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def_drop_side_effect_free(AST_Constant, return_null);
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def_drop_side_effect_free(AST_This, return_null);
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def_drop_side_effect_free(AST_Call, function (compressor, first_in_statement) {
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if (is_nullish_shortcircuited(this, compressor)) {
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return this.expression.drop_side_effect_free(compressor, first_in_statement);
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}
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if (!this.is_callee_pure(compressor)) {
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if (this.expression.is_call_pure(compressor)) {
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var exprs = this.args.slice();
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exprs.unshift(this.expression.expression);
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exprs = trim(exprs, compressor, first_in_statement);
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return exprs && make_sequence(this, exprs);
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}
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if (is_func_expr(this.expression)
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&& (!this.expression.name || !this.expression.name.definition().references.length)) {
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var node = this.clone();
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node.expression.process_expression(false, compressor);
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return node;
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}
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return this;
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}
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var args = trim(this.args, compressor, first_in_statement);
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return args && make_sequence(this, args);
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});
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def_drop_side_effect_free(AST_Accessor, return_null);
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def_drop_side_effect_free(AST_Function, return_null);
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def_drop_side_effect_free(AST_Arrow, return_null);
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def_drop_side_effect_free(AST_Class, function (compressor) {
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const with_effects = [];
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const trimmed_extends = this.extends && this.extends.drop_side_effect_free(compressor);
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if (trimmed_extends)
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with_effects.push(trimmed_extends);
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for (const prop of this.properties) {
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if (prop instanceof AST_ClassStaticBlock) {
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if (prop.body.some(stat => stat.has_side_effects(compressor))) {
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return this;
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} else {
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continue;
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}
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}
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const trimmed_prop = prop.drop_side_effect_free(compressor);
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if (trimmed_prop)
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with_effects.push(trimmed_prop);
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}
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if (!with_effects.length)
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return null;
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return make_sequence(this, with_effects);
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});
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def_drop_side_effect_free(AST_Binary, function (compressor, first_in_statement) {
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var right = this.right.drop_side_effect_free(compressor);
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if (!right)
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return this.left.drop_side_effect_free(compressor, first_in_statement);
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if (lazy_op.has(this.operator)) {
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if (right === this.right)
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return this;
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var node = this.clone();
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node.right = right;
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return node;
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} else {
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var left = this.left.drop_side_effect_free(compressor, first_in_statement);
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if (!left)
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return this.right.drop_side_effect_free(compressor, first_in_statement);
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return make_sequence(this, [left, right]);
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}
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});
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def_drop_side_effect_free(AST_Assign, function (compressor) {
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if (this.logical)
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return this;
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var left = this.left;
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if (left.has_side_effects(compressor)
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|| compressor.has_directive("use strict")
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&& left instanceof AST_PropAccess
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&& left.expression.is_constant()) {
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return this;
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}
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set_flag(this, WRITE_ONLY);
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while (left instanceof AST_PropAccess) {
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left = left.expression;
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}
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if (left.is_constant_expression(compressor.find_parent(AST_Scope))) {
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return this.right.drop_side_effect_free(compressor);
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}
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return this;
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});
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def_drop_side_effect_free(AST_Conditional, function (compressor) {
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var consequent = this.consequent.drop_side_effect_free(compressor);
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var alternative = this.alternative.drop_side_effect_free(compressor);
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if (consequent === this.consequent && alternative === this.alternative)
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return this;
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if (!consequent)
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return alternative ? make_node(AST_Binary, this, {
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operator: "||",
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left: this.condition,
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right: alternative
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}) : this.condition.drop_side_effect_free(compressor);
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if (!alternative)
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return make_node(AST_Binary, this, {
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operator: "&&",
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left: this.condition,
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right: consequent
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});
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var node = this.clone();
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node.consequent = consequent;
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node.alternative = alternative;
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return node;
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});
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def_drop_side_effect_free(AST_Unary, function (compressor, first_in_statement) {
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if (unary_side_effects.has(this.operator)) {
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if (!this.expression.has_side_effects(compressor)) {
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set_flag(this, WRITE_ONLY);
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} else {
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clear_flag(this, WRITE_ONLY);
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}
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return this;
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}
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if (this.operator == "typeof" && this.expression instanceof AST_SymbolRef)
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return null;
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var expression = this.expression.drop_side_effect_free(compressor, first_in_statement);
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if (first_in_statement && expression && is_iife_call(expression)) {
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if (expression === this.expression && this.operator == "!")
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return this;
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return expression.negate(compressor, first_in_statement);
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}
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return expression;
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});
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def_drop_side_effect_free(AST_SymbolRef, function (compressor) {
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const safe_access = this.is_declared(compressor)
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|| pure_prop_access_globals.has(this.name);
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return safe_access ? null : this;
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});
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def_drop_side_effect_free(AST_Object, function (compressor, first_in_statement) {
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var values = trim(this.properties, compressor, first_in_statement);
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return values && make_sequence(this, values);
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});
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def_drop_side_effect_free(AST_ObjectProperty, function (compressor, first_in_statement) {
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const computed_key = this instanceof AST_ObjectKeyVal && this.key instanceof AST_Node;
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const key = computed_key && this.key.drop_side_effect_free(compressor, first_in_statement);
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const value = this.value && this.value.drop_side_effect_free(compressor, first_in_statement);
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if (key && value) {
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return make_sequence(this, [key, value]);
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}
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return key || value;
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});
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def_drop_side_effect_free(AST_ClassProperty, function (compressor) {
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const key = this.computed_key() && this.key.drop_side_effect_free(compressor);
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const value = this.static && this.value
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&& this.value.drop_side_effect_free(compressor);
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if (key && value)
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return make_sequence(this, [key, value]);
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return key || value || null;
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});
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def_drop_side_effect_free(AST_ConciseMethod, function () {
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return this.computed_key() ? this.key : null;
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});
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def_drop_side_effect_free(AST_ObjectGetter, function () {
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return this.computed_key() ? this.key : null;
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});
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def_drop_side_effect_free(AST_ObjectSetter, function () {
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return this.computed_key() ? this.key : null;
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});
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def_drop_side_effect_free(AST_Array, function (compressor, first_in_statement) {
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var values = trim(this.elements, compressor, first_in_statement);
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return values && make_sequence(this, values);
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});
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def_drop_side_effect_free(AST_Dot, function (compressor, first_in_statement) {
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if (is_nullish_shortcircuited(this, compressor)) {
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return this.expression.drop_side_effect_free(compressor, first_in_statement);
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}
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if (this.expression.may_throw_on_access(compressor)) return this;
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return this.expression.drop_side_effect_free(compressor, first_in_statement);
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});
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def_drop_side_effect_free(AST_Sub, function (compressor, first_in_statement) {
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if (is_nullish_shortcircuited(this, compressor)) {
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return this.expression.drop_side_effect_free(compressor, first_in_statement);
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}
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if (this.expression.may_throw_on_access(compressor)) return this;
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var expression = this.expression.drop_side_effect_free(compressor, first_in_statement);
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if (!expression)
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return this.property.drop_side_effect_free(compressor, first_in_statement);
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var property = this.property.drop_side_effect_free(compressor);
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if (!property)
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return expression;
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return make_sequence(this, [expression, property]);
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});
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def_drop_side_effect_free(AST_Chain, function (compressor, first_in_statement) {
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return this.expression.drop_side_effect_free(compressor, first_in_statement);
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});
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def_drop_side_effect_free(AST_Sequence, function (compressor) {
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var last = this.tail_node();
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var expr = last.drop_side_effect_free(compressor);
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if (expr === last)
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return this;
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var expressions = this.expressions.slice(0, -1);
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if (expr)
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expressions.push(expr);
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if (!expressions.length) {
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return make_node(AST_Number, this, { value: 0 });
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}
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return make_sequence(this, expressions);
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});
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def_drop_side_effect_free(AST_Expansion, function (compressor, first_in_statement) {
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return this.expression.drop_side_effect_free(compressor, first_in_statement);
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});
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def_drop_side_effect_free(AST_TemplateSegment, return_null);
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def_drop_side_effect_free(AST_TemplateString, function (compressor) {
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var values = trim(this.segments, compressor, first_in_statement);
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return values && make_sequence(this, values);
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});
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