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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
<mihai.bazon@gmail.com>
http://mihai.bazon.net/blog
Distributed under the BSD license:
Copyright 2012 (c) Mihai Bazon <mihai.bazon@gmail.com>
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
* Redistributions of source code must retain the above
copyright notice, this list of conditions and the following
disclaimer.
* Redistributions in binary form must reproduce the above
copyright notice, this list of conditions and the following
disclaimer in the documentation and/or other materials
provided with the distribution.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER “AS IS” AND ANY
EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER BE
LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR
TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
SUCH DAMAGE.
***********************************************************************/
"use strict";
function 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, {
arguments : !false_by_default,
assignments : !false_by_default,
booleans : !false_by_default,
collapse_vars : !false_by_default,
comparisons : !false_by_default,
conditionals : !false_by_default,
dead_code : !false_by_default,
directives : !false_by_default,
drop_console : false,
drop_debugger : !false_by_default,
evaluate : !false_by_default,
expression : false,
global_defs : false,
hoist_funs : false,
hoist_props : !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_funcs : !false_by_default,
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"]),
typeofs : !false_by_default,
unsafe : false,
unsafe_comps : false,
unsafe_Function : false,
unsafe_math : false,
unsafe_proto : false,
unsafe_regexp : false,
unsafe_undefined: 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)) {
global_defs[key.slice(1)] = parse(global_defs[key], {
expression: true
});
}
}
if (this.options["inline"] === true) this.options["inline"] = 3;
var pure_funcs = this.options["pure_funcs"];
if (typeof pure_funcs == "function") {
this.pure_funcs = pure_funcs;
} else if (typeof pure_funcs == "string") {
this.pure_funcs = function(node) {
return pure_funcs !== node.expression.print_to_string();
};
} else if (Array.isArray(pure_funcs)) {
this.pure_funcs = function(node) {
return pure_funcs.indexOf(node.expression.print_to_string()) < 0;
};
} else {
this.pure_funcs = 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"];
this.toplevel = typeof toplevel == "string" ? {
funcs: /funcs/.test(toplevel),
vars: /vars/.test(toplevel)
} : {
funcs: 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] },
exposed: function(def) {
if (def.global) for (var i = 0, len = def.orig.length; i < len; i++)
if (!this.toplevel[def.orig[i] instanceof AST_SymbolDefun ? "funcs" : "vars"])
return true;
return false;
},
compress: function(node) {
node = node.resolve_defines(this);
if (this.option("expression")) {
node.process_expression(true);
}
var passes = +this.options.passes || 1;
var min_count = 1 / 0;
var stopping = false;
var mangle = { ie8: this.option("ie8") };
for (var pass = 0; pass < passes; pass++) {
node.figure_out_scope(mangle);
if (pass > 0 || this.option("reduce_vars"))
node.reset_opt_flags(this);
node = node.transform(this);
if (passes > 1) {
var count = 0;
node.walk(new TreeWalker(function() {
count++;
}));
this.info("pass " + pass + ": last_count: " + min_count + ", count: " + count);
if (count < min_count) {
min_count = count;
stopping = false;
} else if (stopping) {
break;
} else {
stopping = true;
}
}
}
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 is_scope = node instanceof AST_Scope;
if (is_scope) {
node.hoist_properties(this);
node.hoist_declarations(this);
}
// 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 (is_scope) {
opt.drop_unused(this);
descend(opt, this);
}
if (opt === node) opt._squeezed = true;
return opt;
}
});
(function(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);
}
} else if (node instanceof AST_If) {
node.body = node.body.transform(tt);
if (node.alternative) {
node.alternative = node.alternative.transform(tt);
}
} else if (node instanceof AST_With) {
node.body = node.body.transform(tt);
}
return node;
});
self.transform(tt);
});
function read_property(obj, key) {
key = get_value(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;
}
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
&& !parent.is_expr_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);
}
}
(function(def) {
def(AST_Node, noop);
function reset_def(tw, compressor, def) {
def.assignments = 0;
def.chained = false;
def.direct_access = false;
def.escaped = false;
def.fixed = !def.scope.pinned()
&& !compressor.exposed(def)
&& !(def.init instanceof AST_Function && def.init !== def.scope)
&& def.init;
if (def.fixed instanceof AST_Defun && !all(def.references, function(ref) {
var scope = ref.scope;
do {
if (def.scope === scope) return true;
} while (scope instanceof AST_Function && (scope = scope.parent_scope));
})) {
tw.defun_ids[def.id] = false;
}
def.recursive_refs = 0;
def.references = [];
def.should_replace = undefined;
def.single_use = undefined;
}
function reset_variables(tw, compressor, scope) {
scope.variables.each(function(def) {
reset_def(tw, compressor, def);
if (def.fixed === null) {
def.safe_ids = tw.safe_ids;
mark(tw, def, true);
} else if (def.fixed) {
tw.loop_ids[def.id] = tw.in_loop;
mark(tw, def, true);
}
});
scope.may_call_this = function() {
scope.may_call_this = noop;
if (!scope.contains_this()) return;
scope.functions.each(function(def) {
if (def.init instanceof AST_Defun && !(def.id in tw.defun_ids)) {
tw.defun_ids[def.id] = false;
}
});
};
}
function mark_defun(tw, def) {
if (def.id in tw.defun_ids) {
var marker = tw.defun_ids[def.id];
if (!marker) return;
var visited = tw.defun_visited[def.id];
if (marker === tw.safe_ids) {
if (!visited) return def.fixed;
} else if (visited) {
def.init.enclosed.forEach(function(d) {
if (def.init.variables.get(d.name) === d) return;
if (!safe_to_read(tw, d)) d.fixed = false;
});
} else {
tw.defun_ids[def.id] = false;
}
} else {
if (!tw.in_loop) {
tw.defun_ids[def.id] = tw.safe_ids;
return def.fixed;
}
tw.defun_ids[def.id] = false;
}
}
function walk_defuns(tw, scope) {
scope.functions.each(function(def) {
if (def.init instanceof AST_Defun && !tw.defun_visited[def.id]) {
tw.defun_ids[def.id] = tw.safe_ids;
def.init.walk(tw);
}
});
}
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;
if (def.fixed === null && def.safe_ids) {
def.safe_ids[def.id] = false;
delete def.safe_ids;
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 all(def.orig, function(sym) {
return !(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[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;
}
function mark_escaped(tw, d, scope, node, value, level, depth) {
var parent = tw.parent(level);
if (value && value.is_constant()) return;
if (parent instanceof AST_Assign && parent.operator == "=" && 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) {
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_Binary && lazy_op[parent.operator]
|| parent instanceof AST_Conditional && node !== parent.condition
|| 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;
}
function mark_assignment_to_arguments(node) {
if (!(node instanceof AST_Sub)) return;
var expr = node.expression;
var prop = node.property;
if (expr instanceof AST_SymbolRef && expr.name == "arguments" && prop instanceof AST_Number) {
expr.definition().reassigned = true;
}
}
var suppressor = new TreeWalker(function(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(AST_Accessor, function(tw, descend, compressor) {
push(tw);
reset_variables(tw, compressor, this);
descend();
pop(tw);
walk_defuns(tw, this);
return true;
});
def(AST_Assign, function(tw, descend, compressor) {
var node = this;
var sym = node.left;
if (!(sym instanceof AST_SymbolRef)) {
mark_assignment_to_arguments(sym);
return;
}
var d = sym.definition();
var safe = safe_to_assign(tw, d, sym.scope, node.right);
d.assignments++;
var fixed = d.fixed;
if (!fixed && node.operator != "=") return;
var eq = node.operator == "=";
var value = eq ? node.right : node;
if (is_modified(compressor, tw, node, value, 0)) return;
if (!eq) d.chained = true;
d.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 (!safe) return;
d.references.push(sym);
mark(tw, d, false);
node.right.walk(tw);
mark(tw, d, true);
mark_escaped(tw, d, sym.scope, node, value, 0, 1);
return true;
});
def(AST_Binary, function(tw) {
if (!lazy_op[this.operator]) return;
this.left.walk(tw);
push(tw);
this.right.walk(tw);
pop(tw);
return true;
});
def(AST_Call, function(tw, descend) {
tw.find_parent(AST_Scope).may_call_this();
var exp = this.expression;
if (!(exp instanceof AST_SymbolRef)) return;
var def = exp.definition();
if (!(def.fixed instanceof AST_Defun)) return;
var defun = mark_defun(tw, def);
if (!defun) return;
descend();
defun.walk(tw);
return true;
});
def(AST_Case, function(tw) {
push(tw);
this.expression.walk(tw);
pop(tw);
push(tw);
walk_body(this, tw);
pop(tw);
return true;
});
def(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(AST_Default, function(tw, descend) {
push(tw);
descend();
pop(tw);
return true;
});
def(AST_Defun, function(tw, descend, compressor) {
var id = this.name.definition().id;
if (tw.defun_visited[id]) return true;
if (tw.defun_ids[id] !== tw.safe_ids) return true;
tw.defun_visited[id] = true;
this.inlined = false;
push(tw);
reset_variables(tw, compressor, this);
descend();
pop(tw);
walk_defuns(tw, this);
return true;
});
def(AST_Do, function(tw) {
var 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(AST_For, function(tw) {
if (this.init) this.init.walk(tw);
var 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(AST_ForIn, function(tw) {
this.init.walk(suppressor);
this.object.walk(tw);
var 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(AST_Function, function(tw, descend, compressor) {
var node = this;
node.inlined = false;
push(tw);
reset_variables(tw, compressor, node);
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 (d.fixed === undefined && (!node.uses_arguments || tw.has_directive("use strict"))) {
d.fixed = function() {
return iife.args[i] || make_node(AST_Undefined, iife);
};
tw.loop_ids[d.id] = tw.in_loop;
mark(tw, d, true);
} else {
d.fixed = false;
}
});
}
descend();
pop(tw);
walk_defuns(tw, node);
return true;
});
def(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(AST_LabeledStatement, function(tw) {
push(tw);
this.body.walk(tw);
pop(tw);
return true;
});
def(AST_SymbolCatch, function() {
this.definition().fixed = false;
});
def(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[d.id] = tw.in_loop;
}
var value;
if (d.fixed === undefined || !safe_to_read(tw, d)) {
d.fixed = false;
} else if (d.fixed) {
value = this.fixed_value();
if (value instanceof AST_Lambda && recursive_ref(tw, d)) {
d.recursive_refs++;
} else if (value && ref_once(tw, compressor, d)) {
d.single_use = value instanceof AST_Lambda && !value.pinned()
|| d.scope === this.scope && value.is_constant_expression();
} else {
d.single_use = false;
}
if (is_modified(compressor, tw, this, value, 0, is_immutable(value))) {
if (d.single_use) {
d.single_use = "m";
} else {
d.fixed = false;
}
}
}
mark_escaped(tw, d, this.scope, this, value, 0, 1);
var parent;
if (d.fixed instanceof AST_Defun
&& !((parent = tw.parent()) instanceof AST_Call && parent.expression === this)) {
var defun = mark_defun(tw, d);
if (defun) defun.walk(tw);
}
});
def(AST_Toplevel, function(tw, descend, compressor) {
this.globals.each(function(def) {
reset_def(tw, compressor, def);
});
push(tw);
reset_variables(tw, compressor, this);
descend();
pop(tw);
walk_defuns(tw, this);
return true;
});
def(AST_Try, function(tw) {
push(tw);
walk_body(this, tw);
pop(tw);
if (this.bcatch) {
push(tw);
this.bcatch.walk(tw);
pop(tw);
}
if (this.bfinally) this.bfinally.walk(tw);
return true;
});
def(AST_Unary, function(tw, descend) {
var node = this;
if (node.operator != "++" && node.operator != "--") return;
var exp = node.expression;
if (!(exp instanceof AST_SymbolRef)) {
mark_assignment_to_arguments(exp);
return;
}
var d = exp.definition();
var safe = safe_to_assign(tw, d, exp.scope, true);
d.assignments++;
var fixed = d.fixed;
if (!fixed) return;
d.chained = true;
d.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
})
});
};
if (!safe) return;
d.references.push(exp);
mark(tw, d, true);
return true;
});
def(AST_VarDef, function(tw, descend) {
var node = this;
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[d.id] = tw.in_loop;
mark(tw, d, false);
descend();
mark(tw, d, true);
return true;
} else {
d.fixed = false;
}
}
});
def(AST_While, function(tw, descend) {
var saved_loop = tw.in_loop;
tw.in_loop = this;
push(tw);
descend();
pop(tw);
tw.in_loop = saved_loop;
return true;
});
})(function(node, func) {
node.DEFMETHOD("reduce_vars", func);
});
AST_Toplevel.DEFMETHOD("reset_opt_flags", function(compressor) {
var tw = new TreeWalker(compressor.option("reduce_vars") ? function(node, descend) {
node._squeezed = false;
node._optimized = false;
return node.reduce_vars(tw, descend, compressor);
} : function(node) {
node._squeezed = false;
node._optimized = false;
});
// Flow control for visiting `AST_Defun`s
tw.defun_ids = Object.create(null);
tw.defun_visited = Object.create(null);
// Record the loop body in which `AST_SymbolDeclaration` is first encountered
tw.in_loop = null;
tw.loop_ids = Object.create(null);
// Stack of look-up tables to keep track of whether a `SymbolDef` has been
// properly assigned before use:
// - `push()` & `pop()` when visiting conditional branches
// - backup & restore via `save_ids` when visiting out-of-order sections
tw.safe_ids = Object.create(null);
this.walk(tw);
});
AST_Symbol.DEFMETHOD("fixed_value", function() {
var fixed = this.definition().fixed;
if (!fixed || fixed instanceof AST_Node) return fixed;
return fixed();
});
AST_SymbolRef.DEFMETHOD("is_immutable", function() {
var orig = this.definition().orig;
return orig.length == 1 && orig[0] instanceof AST_SymbolLambda;
});
function is_lhs_read_only(lhs) {
if (lhs instanceof AST_This) return true;
if (lhs instanceof AST_SymbolRef) return lhs.definition().orig[0] instanceof AST_SymbolLambda;
if (lhs instanceof AST_PropAccess) {
lhs = lhs.expression;
if (lhs instanceof AST_SymbolRef) {
if (lhs.is_immutable()) return false;
lhs = lhs.fixed_value();
}
if (!lhs) return true;
if (lhs.is_constant()) return true;
return is_lhs_read_only(lhs);
}
return false;
}
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.reduce(merge_sequence, [])
});
}
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
}));
}
}
function needs_unbinding(compressor, val) {
return val instanceof AST_PropAccess
|| compressor.has_directive("use strict")
&& is_undeclared_ref(val)
&& val.name == "eval";
}
// 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(compressor, parent, orig, val) {
if (parent instanceof AST_UnaryPrefix && parent.operator == "delete"
|| parent.TYPE == "Call" && parent.expression === orig && needs_unbinding(compressor, val)) {
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);
}
return array;
}
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_IterationStatement) {
return x.body instanceof AST_BlockStatement ? x.body : x;
}
return x;
}
function root_expr(prop) {