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enhance dead_code (#3907)

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This commit is contained in:
Alex Lam S.L
2020-05-18 20:53:08 +01:00
committed by GitHub
parent f9b3198714
commit 87046410ef
2 changed files with 30 additions and 0 deletions
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5
lib/compress.js
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@@ -7739,6 +7739,10 @@ merge(Compressor.prototype, {
if (compressor.option("dead_code")) {
if (self.left instanceof AST_PropAccess) {
if (self.operator == "=") {
if (self.left.equivalent_to(self.right)
&& (self.left instanceof AST_Dot || !self.left.property.has_side_effects(compressor))) {
return self.right;
}
var exp = self.left.expression;
if (exp instanceof AST_Lambda
|| !compressor.has_directive("use strict")
@@ -7751,6 +7755,7 @@ merge(Compressor.prototype, {
}
}
} else if (self.left instanceof AST_SymbolRef) {
if (self.operator == "=" && self.left.equivalent_to(self.right)) return self.right;
if (self.left.is_immutable()) return strip_assignment();
var def = self.left.definition();
var scope = def.scope.resolve();

25
test/compress/dead-code.js
View File

@@ -1168,3 +1168,28 @@ redundant_assignments: {
}
expect_stdout: "PASS PASS"
}
self_assignments: {
options = {
dead_code: true,
}
input: {
var a = "PASS", b = 0, l = [ "FAIL", "PASS" ], o = { p: "PASS" };
a = a;
l[0] = l[0];
l[b] = l[b];
l[b++] = l[b++];
o.p = o.p;
console.log(a, b, l[0], o.p);
}
expect: {
var a = "PASS", b = 0, l = [ "FAIL", "PASS" ], o = { p: "PASS" };
a;
l[0];
l[b];
l[b++] = l[b++];
o.p;
console.log(a, b, l[0], o.p);
}
expect_stdout: "PASS 2 PASS PASS"
}