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compress.js
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compress.js
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/***********************************************************************
A JavaScript tokenizer / parser / beautifier / compressor.
https://github.com/mishoo/UglifyJS2
-------------------------------- (C) ---------------------------------
Author: Mihai Bazon
http://mihai.bazon.net/blog
Distributed under the BSD license:
Copyright 2012 (c) Mihai Bazon <[email protected]>
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
* Redistributions of source code must retain the above
copyright notice, this list of conditions and the following
disclaimer.
* Redistributions in binary form must reproduce the above
copyright notice, this list of conditions and the following
disclaimer in the documentation and/or other materials
provided with the distribution.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER “AS IS” AND ANY
EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER BE
LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR
TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
SUCH DAMAGE.
***********************************************************************/
"use strict";
function Compressor(options, false_by_default) {
if (!(this instanceof Compressor))
return new Compressor(options, false_by_default);
TreeTransformer.call(this, this.before, this.after);
this.options = defaults(options, {
booleans : !false_by_default,
cascade : !false_by_default,
collapse_vars : !false_by_default,
comparisons : !false_by_default,
conditionals : !false_by_default,
dead_code : !false_by_default,
drop_console : false,
drop_debugger : !false_by_default,
evaluate : !false_by_default,
expression : false,
global_defs : {},
hoist_funs : !false_by_default,
hoist_vars : false,
ie8 : false,
if_return : !false_by_default,
inline : !false_by_default,
join_vars : !false_by_default,
keep_fargs : true,
keep_fnames : false,
keep_infinity : false,
loops : !false_by_default,
negate_iife : !false_by_default,
passes : 1,
properties : !false_by_default,
pure_getters : !false_by_default && "strict",
pure_funcs : null,
reduce_vars : !false_by_default,
sequences : !false_by_default,
side_effects : !false_by_default,
switches : !false_by_default,
top_retain : null,
toplevel : !!(options && options["top_retain"]),
unsafe : false,
unsafe_comps : false,
unsafe_Func : false,
unsafe_math : false,
unsafe_proto : false,
unsafe_regexp : false,
unused : !false_by_default,
warnings : false,
}, true);
var global_defs = this.options["global_defs"];
if (typeof global_defs == "object") for (var key in global_defs) {
if (/^@/.test(key) && HOP(global_defs, key)) {
var ast = parse(global_defs[key]);
if (ast.body.length == 1 && ast.body[0] instanceof AST_SimpleStatement) {
global_defs[key.slice(1)] = ast.body[0].body;
} else throw new Error(string_template("Can't handle expression: {value}", {
value: global_defs[key]
}));
}
}
var pure_funcs = this.options["pure_funcs"];
if (typeof pure_funcs == "function") {
this.pure_funcs = pure_funcs;
} else {
this.pure_funcs = pure_funcs ? function(node) {
return pure_funcs.indexOf(node.expression.print_to_string()) < 0;
} : return_true;
}
var top_retain = this.options["top_retain"];
if (top_retain instanceof RegExp) {
this.top_retain = function(def) {
return top_retain.test(def.name);
};
} else if (typeof top_retain == "function") {
this.top_retain = top_retain;
} else if (top_retain) {
if (typeof top_retain == "string") {
top_retain = top_retain.split(/,/);
}
this.top_retain = function(def) {
return top_retain.indexOf(def.name) >= 0;
};
}
var toplevel = this.options["toplevel"];
if (typeof toplevel == "string") {
this.toplevel.funcs = /funcs/.test(toplevel);
this.toplevel.vars = /vars/.test(toplevel);
} else {
this.toplevel = toplevel ? return_true : return_false;
this.toplevel.funcs = this.toplevel.vars = toplevel;
}
var sequences = this.options["sequences"];
this.sequences_limit = sequences == 1 ? 800 : sequences | 0;
this.warnings_produced = {};
};
Compressor.prototype = new TreeTransformer;
merge(Compressor.prototype, {
option: function(key) { return this.options[key] },
toplevel: function(def) {
for (var i = 0, len = def.orig.length; i < len; i++)
if (!this.toplevel[def.orig[i] instanceof AST_SymbolDefun ? "funcs" : "vars"])
return false;
return true;
},
compress: function(node) {
if (this.option("expression")) {
node.process_expression(true);
}
var passes = +this.options.passes || 1;
for (var pass = 0; pass < passes && pass < 3; ++pass) {
if (pass > 0 || this.option("reduce_vars"))
node.reset_opt_flags(this, true);
node = node.transform(this);
}
if (this.option("expression")) {
node.process_expression(false);
}
return node;
},
info: function() {
if (this.options.warnings == "verbose") {
AST_Node.warn.apply(AST_Node, arguments);
}
},
warn: function(text, props) {
if (this.options.warnings) {
// only emit unique warnings
var message = string_template(text, props);
if (!(message in this.warnings_produced)) {
this.warnings_produced[message] = true;
AST_Node.warn.apply(AST_Node, arguments);
}
}
},
clear_warnings: function() {
this.warnings_produced = {};
},
before: function(node, descend, in_list) {
if (node._squeezed) return node;
var was_scope = false;
if (node instanceof AST_Scope) {
node = node.hoist_declarations(this);
was_scope = true;
}
// Before https://github.com/mishoo/UglifyJS2/pull/1602 AST_Node.optimize()
// would call AST_Node.transform() if a different instance of AST_Node is
// produced after OPT().
// This corrupts TreeWalker.stack, which cause AST look-ups to malfunction.
// Migrate and defer all children's AST_Node.transform() to below, which
// will now happen after this parent AST_Node has been properly substituted
// thus gives a consistent AST snapshot.
descend(node, this);
// Existing code relies on how AST_Node.optimize() worked, and omitting the
// following replacement call would result in degraded efficiency of both
// output and performance.
descend(node, this);
var opt = node.optimize(this);
if (was_scope && opt instanceof AST_Scope) {
opt.drop_unused(this);
descend(opt, this);
}
if (opt === node) opt._squeezed = true;
return opt;
}
});
(function(){
function OPT(node, optimizer) {
node.DEFMETHOD("optimize", function(compressor){
var self = this;
if (self._optimized) return self;
if (compressor.has_directive("use asm")) return self;
var opt = optimizer(self, compressor);
opt._optimized = true;
return opt;
});
};
OPT(AST_Node, function(self, compressor){
return self;
});
AST_Node.DEFMETHOD("equivalent_to", function(node){
return this.TYPE == node.TYPE && this.print_to_string() == node.print_to_string();
});
AST_Scope.DEFMETHOD("process_expression", function(insert, compressor) {
var self = this;
var tt = new TreeTransformer(function(node) {
if (insert && node instanceof AST_SimpleStatement) {
return make_node(AST_Return, node, {
value: node.body
});
}
if (!insert && node instanceof AST_Return) {
if (compressor) {
var value = node.value && node.value.drop_side_effect_free(compressor, true);
return value ? make_node(AST_SimpleStatement, node, {
body: value
}) : make_node(AST_EmptyStatement, node);
}
return make_node(AST_SimpleStatement, node, {
body: node.value || make_node(AST_UnaryPrefix, node, {
operator: "void",
expression: make_node(AST_Number, node, {
value: 0
})
})
});
}
if (node instanceof AST_Lambda && node !== self) {
return node;
}
if (node instanceof AST_Block) {
var index = node.body.length - 1;
if (index >= 0) {
node.body[index] = node.body[index].transform(tt);
}
}
if (node instanceof AST_If) {
node.body = node.body.transform(tt);
if (node.alternative) {
node.alternative = node.alternative.transform(tt);
}
}
if (node instanceof AST_With) {
node.body = node.body.transform(tt);
}
return node;
});
self.transform(tt);
});
AST_Node.DEFMETHOD("reset_opt_flags", function(compressor, rescan) {
var reduce_vars = rescan && compressor.option("reduce_vars");
var safe_ids = Object.create(null);
var suppressor = new TreeWalker(function(node) {
if (node instanceof AST_Symbol) {
var d = node.definition();
if (node instanceof AST_SymbolRef) d.references.push(node);
d.fixed = false;
}
});
var tw = new TreeWalker(function(node, descend) {
node._squeezed = false;
node._optimized = false;
if (reduce_vars) {
if (node instanceof AST_Toplevel) node.globals.each(reset_def);
if (node instanceof AST_Scope) node.variables.each(reset_def);
if (node instanceof AST_SymbolRef) {
var d = node.definition();
d.references.push(node);
if (d.fixed === undefined || !safe_to_read(d)
|| is_modified(node, 0, is_immutable(node.fixed_value()))) {
d.fixed = false;
} else {
var parent = tw.parent();
if (parent instanceof AST_Assign && parent.operator == "=" && node === parent.right
|| parent instanceof AST_Call && node !== parent.expression
|| parent instanceof AST_Return && node === parent.value && node.scope !== d.scope
|| parent instanceof AST_VarDef && node === parent.value) {
d.escaped = true;
}
}
}
if (node instanceof AST_SymbolCatch) {
node.definition().fixed = false;
}
if (node instanceof AST_VarDef) {
var d = node.name.definition();
if (d.fixed === undefined || safe_to_assign(d, node.value)) {
if (node.value) {
d.fixed = function() {
return node.value;
};
mark(d, false);
descend();
} else {
d.fixed = null;
}
mark(d, true);
return true;
} else if (node.value) {
d.fixed = false;
}
}
if (node instanceof AST_Assign
&& node.operator == "="
&& node.left instanceof AST_SymbolRef) {
var d = node.left.definition();
if (safe_to_assign(d, node.right)) {
d.references.push(node.left);
d.fixed = function() {
return node.right;
};
mark(d, false);
node.right.walk(tw);
mark(d, true);
return true;
}
}
if (node instanceof AST_Defun) {
var d = node.name.definition();
if (d.global && !compressor.toplevel(d) || safe_to_read(d)) {
d.fixed = false;
} else {
d.fixed = node;
mark(d, true);
}
var save_ids = safe_ids;
safe_ids = Object.create(null);
descend();
safe_ids = save_ids;
return true;
}
if (node instanceof AST_Function) {
push();
var iife;
if (!node.name
&& (iife = tw.parent()) instanceof AST_Call
&& iife.expression === node) {
// 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.
node.argnames.forEach(function(arg, i) {
var d = arg.definition();
if (!node.uses_arguments && d.fixed === undefined) {
d.fixed = function() {
return iife.args[i] || make_node(AST_Undefined, iife);
};
mark(d, true);
} else {
d.fixed = false;
}
});
}
descend();
pop();
return true;
}
if (node instanceof AST_Accessor) {
var save_ids = safe_ids;
safe_ids = Object.create(null);
descend();
safe_ids = save_ids;
return true;
}
if (node instanceof AST_Binary
&& (node.operator == "&&" || node.operator == "||")) {
node.left.walk(tw);
push();
node.right.walk(tw);
pop();
return true;
}
if (node instanceof AST_Conditional) {
node.condition.walk(tw);
push();
node.consequent.walk(tw);
pop();
push();
node.alternative.walk(tw);
pop();
return true;
}
if (node instanceof AST_If) {
node.condition.walk(tw);
push();
node.body.walk(tw);
pop();
if (node.alternative) {
push();
node.alternative.walk(tw);
pop();
}
return true;
}
if (node instanceof AST_DWLoop) {
push();
node.condition.walk(tw);
node.body.walk(tw);
pop();
return true;
}
if (node instanceof AST_LabeledStatement) {
push();
node.body.walk(tw);
pop();
return true;
}
if (node instanceof AST_For) {
if (node.init) node.init.walk(tw);
if (node.condition) {
push();
node.condition.walk(tw);
pop();
}
push();
node.body.walk(tw);
pop();
if (node.step) {
push();
node.step.walk(tw);
pop();
}
return true;
}
if (node instanceof AST_ForIn) {
node.init.walk(suppressor);
node.object.walk(tw);
push();
node.body.walk(tw);
pop();
return true;
}
if (node instanceof AST_Try) {
push();
walk_body(node, tw);
pop();
if (node.bcatch) {
push();
node.bcatch.walk(tw);
pop();
}
if (node.bfinally) node.bfinally.walk(tw);
return true;
}
if (node instanceof AST_SwitchBranch) {
push();
descend();
pop();
return true;
}
}
});
this.walk(tw);
function mark(def, safe) {
safe_ids[def.id] = safe;
}
function safe_to_read(def) {
if (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;
}
}
function safe_to_assign(def, value) {
if (!HOP(safe_ids, def.id)) return false;
if (!safe_to_read(def)) return false;
if (def.fixed === false) return false;
if (def.fixed != null && (!value || def.references.length > 0)) return false;
return !def.orig.some(function(sym) {
return sym instanceof AST_SymbolDefun
|| sym instanceof AST_SymbolLambda;
});
}
function push() {
safe_ids = Object.create(safe_ids);
}
function pop() {
safe_ids = Object.getPrototypeOf(safe_ids);
}
function reset_def(def) {
def.escaped = false;
if (def.scope.uses_eval) {
def.fixed = false;
} else if (!def.global || compressor.toplevel(def)) {
def.fixed = undefined;
} else {
def.fixed = false;
}
def.references = [];
def.should_replace = undefined;
}
function is_immutable(value) {
return value && value.is_constant() || value instanceof AST_Lambda;
}
function is_modified(node, level, immutable) {
var parent = tw.parent(level);
if (is_lhs(node, parent)
|| !immutable && parent instanceof AST_Call && parent.expression === node) {
return true;
} else if (parent instanceof AST_PropAccess && parent.expression === node) {
return !immutable && is_modified(parent, level + 1);
}
}
});
AST_SymbolRef.DEFMETHOD("fixed_value", function() {
var fixed = this.definition().fixed;
if (!fixed || fixed instanceof AST_Node) return fixed;
return fixed();
});
function is_lhs_read_only(lhs) {
return lhs instanceof AST_SymbolRef && lhs.definition().orig[0] instanceof AST_SymbolLambda;
}
function find_variable(compressor, name) {
var scope, i = 0;
while (scope = compressor.parent(i++)) {
if (scope instanceof AST_Scope) break;
if (scope instanceof AST_Catch) {
scope = scope.argname.definition().scope;
break;
}
}
return scope.find_variable(name);
}
function make_node(ctor, orig, props) {
if (!props) props = {};
if (orig) {
if (!props.start) props.start = orig.start;
if (!props.end) props.end = orig.end;
}
return new ctor(props);
};
function make_sequence(orig, expressions) {
if (expressions.length == 1) return expressions[0];
return make_node(AST_Sequence, orig, {
expressions: expressions
});
}
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: val });
}
throw new Error(string_template("Can't handle constant of type: {type}", {
type: typeof val
}));
}
};
// we shouldn't compress (1,func)(something) to
// func(something) because that changes the meaning of
// the func (becomes lexical instead of global).
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_PropAccess || val instanceof AST_SymbolRef && val.name == "eval")) {
return make_sequence(orig, [ make_node(AST_Number, orig, { value: 0 }), val ]);
}
return val;
}
function merge_sequence(array, node) {
if (node instanceof AST_Sequence) {
array.push.apply(array, node.expressions);
} else {
array.push(node);
}
}
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");
};
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;
};
function loop_body(x) {
if (x instanceof AST_Switch) return x;
if (x instanceof AST_For || x instanceof AST_ForIn || x instanceof AST_DWLoop) {
return (x.body instanceof AST_BlockStatement ? x.body : x);
}
return x;
};
function is_iife_call(node) {
if (node instanceof AST_Call && !(node instanceof AST_New)) {
return node.expression instanceof AST_Function || is_iife_call(node.expression);
}
return false;
}
function tighten_body(statements, compressor) {
var CHANGED, max_iter = 10;
do {
CHANGED = false;
statements = eliminate_spurious_blocks(statements);
if (compressor.option("dead_code")) {
statements = eliminate_dead_code(statements, compressor);
}
if (compressor.option("if_return")) {
statements = handle_if_return(statements, compressor);
}
if (compressor.sequences_limit > 0) {
statements = sequencesize(statements, compressor);
}
if (compressor.option("join_vars")) {
statements = join_consecutive_vars(statements, compressor);
}
if (compressor.option("collapse_vars")) {
statements = collapse(statements, compressor);
}
} while (CHANGED && max_iter-- > 0);
return statements;
// Search from right to left for assignment-like expressions:
// - `var a = x;`
// - `a = x;`
// - `++a`
// For each candidate, scan from left to right for first usage, then try
// to fold assignment into the site for compression.
// Will not attempt to collapse assignments into or past code blocks
// which are not sequentially executed, e.g. loops and conditionals.
function collapse(statements, compressor) {
var scope = compressor.find_parent(AST_Scope);
if (scope.uses_eval || scope.uses_with) return statements;
var candidates = [];
var stat_index = statements.length;
while (--stat_index >= 0) {
extract_candidates(statements[stat_index]);
while (candidates.length > 0) {
var candidate = candidates.pop();
var lhs = get_lhs(candidate);
if (!lhs || is_lhs_read_only(lhs)) continue;
var lvalues = get_lvalues(candidate);
if (lhs instanceof AST_SymbolRef) lvalues[lhs.name] = false;
var side_effects = value_has_side_effects(candidate);
var hit = false, abort = false, replaced = false;
var tt = new TreeTransformer(function(node, descend) {
if (abort) return node;
// Skip nodes before `candidate` as quickly as possible
if (!hit) {
if (node === candidate) {
hit = true;
return node;
}
return;
}
// Stop immediately if these node types are encountered
var parent = tt.parent();
if (node instanceof AST_Assign && node.operator != "=" && lhs.equivalent_to(node.left)
|| node instanceof AST_Debugger
|| node instanceof AST_IterationStatement && !(node instanceof AST_For)
|| node instanceof AST_SymbolRef && node.undeclared()
|| node instanceof AST_Try
|| node instanceof AST_With
|| parent instanceof AST_For && node !== parent.init) {
abort = true;
return node;
}
// Replace variable with assignment when found
if (!(node instanceof AST_SymbolDeclaration)
&& !is_lhs(node, parent)
&& lhs.equivalent_to(node)) {
CHANGED = replaced = abort = true;
compressor.info("Collapsing {name} [{file}:{line},{col}]", {
name: node.print_to_string(),
file: node.start.file,
line: node.start.line,
col: node.start.col
});
if (candidate instanceof AST_UnaryPostfix) {
return make_node(AST_UnaryPrefix, candidate, candidate);
}
if (candidate instanceof AST_VarDef) {
var def = candidate.name.definition();
if (def.references.length == 1 && (!def.global || compressor.toplevel(def))) {
return maintain_this_binding(parent, node, candidate.value);
}
return make_node(AST_Assign, candidate, {
operator: "=",
left: make_node(AST_SymbolRef, candidate.name, candidate.name),
right: candidate.value
});
}
return candidate;
}
// These node types have child nodes that execute sequentially,
// but are otherwise not safe to scan into or beyond them.
var sym;
if (node instanceof AST_Call
|| node instanceof AST_Exit
|| node instanceof AST_PropAccess
|| node instanceof AST_SymbolRef
&& (lvalues[node.name]
|| side_effects && !references_in_scope(node.definition()))
|| (sym = lhs_or_def(node)) && get_symbol(sym).name in lvalues
|| parent instanceof AST_Binary
&& (parent.operator == "&&" || parent.operator == "||")
|| parent instanceof AST_Case
|| parent instanceof AST_Conditional
|| parent instanceof AST_For
|| parent instanceof AST_If) {
if (!(node instanceof AST_Scope)) descend(node, tt);
abort = true;
return node;
}
// Skip (non-executed) functions and (leading) default case in switch statements
if (node instanceof AST_Default || node instanceof AST_Scope) return node;
});
for (var i = stat_index; !abort && i < statements.length; i++) {
statements[i].transform(tt);
}
if (replaced && !remove_candidate(candidate)) statements.splice(stat_index, 1);
}
}
return statements;
function extract_candidates(expr) {
if (expr instanceof AST_Assign && !expr.left.has_side_effects(compressor)
|| expr instanceof AST_Unary && (expr.operator == "++" || expr.operator == "--")) {
candidates.push(expr);
} else if (expr instanceof AST_Sequence) {
expr.expressions.forEach(extract_candidates);
} else if (expr instanceof AST_Definitions) {
expr.definitions.forEach(function(var_def) {
if (var_def.value) candidates.push(var_def);
});
} else if (expr instanceof AST_SimpleStatement) {
extract_candidates(expr.body);
} else if (expr instanceof AST_For && expr.init) {
extract_candidates(expr.init);
}
}
function get_lhs(expr) {
if (expr instanceof AST_VarDef) {
var def = expr.name.definition();
if (def.orig.length > 1
|| def.references.length == 1 && (!def.global || compressor.toplevel(def))) {
return make_node(AST_SymbolRef, expr.name, expr.name);
}
} else {
return expr[expr instanceof AST_Assign ? "left" : "expression"];
}
}
function get_symbol(node) {
while (node instanceof AST_PropAccess) node = node.expression;
return node;
}
function get_lvalues(expr) {
var lvalues = Object.create(null);
if (expr instanceof AST_Unary) return lvalues;
var scope;
var tw = new TreeWalker(function(node, descend) {
if (node instanceof AST_Scope) {
var save_scope = scope;
descend();
scope = save_scope;
return true;
}
if (node instanceof AST_SymbolRef || node instanceof AST_PropAccess) {
var sym = get_symbol(node);
if (sym instanceof AST_SymbolRef) {
lvalues[sym.name] = lvalues[sym.name] || is_lhs(node, tw.parent());
}
}
});
expr[expr instanceof AST_Assign ? "right" : "value"].walk(tw);
return lvalues;
}
function lhs_or_def(node) {
if (node instanceof AST_VarDef) return node.value && node.name;
return is_lhs(node.left, node);
}
function remove_candidate(expr) {
var found = false;
return statements[stat_index].transform(new TreeTransformer(function(node, descend, in_list) {
if (found) return node;
if (node === expr) {
found = true;
if (node instanceof AST_VarDef) {
remove(node.name.definition().orig, node.name);
}
return in_list ? MAP.skip : null;
}
}, function(node) {
if (node instanceof AST_Sequence) switch (node.expressions.length) {
case 0: return null;
case 1: return node.expressions[0];
}
if (node instanceof AST_Definitions && node.definitions.length == 0
|| node instanceof AST_SimpleStatement && !node.body) {
return null;
}
}));
}
function value_has_side_effects(expr) {
if (expr instanceof AST_Unary) return false;
return expr[expr instanceof AST_Assign ? "right" : "value"].has_side_effects(compressor);
}
function references_in_scope(def) {
if (def.orig.length == 1 && def.orig[0] instanceof AST_SymbolDefun) return true;
if (def.scope !== scope) return false;
return def.references.every(function(ref) {
return ref.scope === scope;
});
}
}
function eliminate_spurious_blocks(statements) {
var seen_dirs = [];
return statements.reduce(function(a, stat){
if (stat instanceof AST_BlockStatement) {
CHANGED = true;
a.push.apply(a, eliminate_spurious_blocks(stat.body));
} else if (stat instanceof AST_EmptyStatement) {
CHANGED = true;
} else if (stat instanceof AST_Directive) {
if (seen_dirs.indexOf(stat.value) < 0) {
a.push(stat);
seen_dirs.push(stat.value);
} else {
CHANGED = true;
}
} else {
a.push(stat);
}
return a;
}, []);
};
function handle_if_return(statements, compressor) {
var self = compressor.self();
var multiple_if_returns = has_multiple_if_returns(statements);
var in_lambda = self instanceof AST_Lambda;
var ret = []; // Optimized statements, build from tail to front
loop: for (var i = statements.length; --i >= 0;) {
var stat = statements[i];
switch (true) {
case (in_lambda && stat instanceof AST_Return && !stat.value && ret.length == 0):
CHANGED = true;
// note, ret.length is probably always zero
// because we drop unreachable code before this
// step. nevertheless, it's good to check.
continue loop;
case stat instanceof AST_If:
var ab = aborts(stat.body);
if (can_merge_flow(ab)) {
if (ab.label) {
remove(ab.label.thedef.references, ab);
}
CHANGED = true;
var funs = extract_functions_from_statement_array(ret);
var body = as_statement_array_with_return(stat.body, ab);
stat = stat.clone();
stat.condition = stat.condition.negate(compressor);
stat.body = make_node(AST_BlockStatement, stat, {
body: as_statement_array(stat.alternative).concat(ret)
});
stat.alternative = make_node(AST_BlockStatement, stat, {
body: body
});
ret = [ stat.transform(compressor) ].concat(funs);
continue loop;
}
var ab = aborts(stat.alternative);
if (can_merge_flow(ab)) {
if (ab.label) {
remove(ab.label.thedef.references, ab);
}
CHANGED = true;
var funs = extract_functions_from_statement_array(ret);
stat = stat.clone();
stat.body = make_node(AST_BlockStatement, stat.body, {
body: as_statement_array(stat.body).concat(ret)
});
var body = as_statement_array_with_return(stat.alternative, ab);
stat.alternative = make_node(AST_BlockStatement, stat.alternative, {
body: body
});
ret = [ stat.transform(compressor) ].concat(funs);
continue loop;
}
if (stat.body instanceof AST_Return) {
var value = stat.body.value;
//---
// pretty silly case, but:
// if (foo()) return; return; ==> foo(); return;
if ((in_lambda && ret.length == 0 || ret[0] instanceof AST_Return && !ret[0].value)
&& !value && !stat.alternative) {
CHANGED = true;
var cond = make_node(AST_SimpleStatement, stat.condition, {
body: stat.condition
});
ret.unshift(cond);
continue loop;
}
//---
// if (foo()) return x; return y; ==> return foo() ? x : y;
if (ret[0] instanceof AST_Return && value && ret[0].value && !stat.alternative) {
CHANGED = true;
stat = stat.clone();
stat.alternative = ret[0];
ret[0] = stat.transform(compressor);
continue loop;
}
//---
// if (foo()) return x; [ return ; ] ==> return foo() ? x : undefined;
if (multiple_if_returns && (ret.length == 0 || ret[0] instanceof AST_Return)
&& value && !stat.alternative && in_lambda) {
CHANGED = true;
stat = stat.clone();
stat.alternative = ret[0] || make_node(AST_Return, stat, {
value: null
});
ret[0] = stat.transform(compressor);