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Better fix for #343

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We can in fact lift sequences, but only if the operation is assignment and
the left-hand side has no side effects nor property access -- that should
guarantee that whatever we place before it cannot affect the sense of the
assignment.

Dropped contrived test case (too hard to support it now), added a more
meaningful one.
This commit is contained in:
Mihai Bazon
2013-11-06 10:47:36 +02:00
parent 19e2fb134d
commit eab99a1c3d
2 changed files with 22 additions and 2 deletions
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18
lib/compress.js
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@@ -1865,6 +1865,14 @@ merge(Compressor.prototype, {
return self.evaluate(compressor)[0];
});
function has_side_effects_or_prop_access(node, compressor) {
var save_pure_getters = compressor.option("pure_getters");
compressor.options.pure_getters = false;
var ret = node.has_side_effects(compressor);
compressor.options.pure_getters = save_pure_getters;
return ret;
}
AST_Binary.DEFMETHOD("lift_sequences", function(compressor){
if (compressor.option("sequences")) {
if (this.left instanceof AST_Seq) {
@@ -1875,6 +1883,16 @@ merge(Compressor.prototype, {
seq = AST_Seq.from_array(x).transform(compressor);
return seq;
}
if (this.right instanceof AST_Seq
&& this instanceof AST_Assign
&& !has_side_effects_or_prop_access(this.left, compressor)) {
var seq = this.right;
var x = seq.to_array();
this.right = x.pop();
x.push(this);
seq = AST_Seq.from_array(x).transform(compressor);
return seq;
}
}
return this;
});