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improve unused on assign-only symbols (#2568)

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This commit is contained in:
Alex Lam S.L
2017-12-09 06:19:29 +08:00
committed by GitHub
parent 74a2f53683
commit 0aff037a35
2 changed files with 113 additions and 75 deletions
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38
lib/compress.js
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@@ -2487,6 +2487,20 @@ merge(Compressor.prototype, {
// 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) {
var sym = assign_as_unused(node);
if (sym instanceof AST_SymbolRef
&& !(sym.definition().id in in_use_ids)) {
if (node instanceof AST_Assign) {
return maintain_this_binding(parent, node, node.right.transform(tt));
}
return make_node(AST_Number, node, {
value: 0
});
}
}
if (scope !== self) return;
if (node instanceof AST_Function
&& node.name
&& !compressor.option("keep_fnames")) {
@@ -2520,9 +2534,7 @@ merge(Compressor.prototype, {
def.eliminated++;
return make_node(AST_EmptyStatement, node);
}
return node;
}
var parent = tt.parent();
if (node instanceof AST_Definitions && !(parent instanceof AST_ForIn && parent.init === node)) {
// place uninitialized names at the start
var body = [], head = [], tail = [];
@@ -2602,18 +2614,6 @@ merge(Compressor.prototype, {
});
}
}
if (drop_vars) {
var sym = assign_as_unused(node);
if (sym instanceof AST_SymbolRef
&& !(sym.definition().id in in_use_ids)) {
if (node instanceof AST_Assign) {
return maintain_this_binding(parent, node, node.right.transform(tt));
}
return make_node(AST_Number, node, {
value: 0
});
}
}
// certain combination of unused name + side effect leads to:
// https://github.com/mishoo/UglifyJS2/issues/44
// https://github.com/mishoo/UglifyJS2/issues/1830
@@ -2645,8 +2645,13 @@ merge(Compressor.prototype, {
}
return node;
}
if (node instanceof AST_Scope && node !== self)
if (node instanceof AST_Scope) {
var save_scope = scope;
scope = node;
descend(node, this);
scope = save_scope;
return node;
}
function template(sym) {
return {
@@ -2662,8 +2667,7 @@ merge(Compressor.prototype, {
function scan_ref_scoped(node, descend) {
var sym;
if (scope === self
&& (sym = assign_as_unused(node)) instanceof AST_SymbolRef
if ((sym = assign_as_unused(node)) instanceof AST_SymbolRef
&& self.variables.get(sym.name) === sym.definition()) {
if (node instanceof AST_Assign) node.right.walk(tw);
return true;