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Better fix for equality of typeof ... against "undefined"

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This commit is contained in:
Mihai Bazon
2013-05-08 16:22:39 +03:00
parent a1958aad56
commit a6ed2c84ac
2 changed files with 26 additions and 14 deletions
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27
lib/compress.js
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@@ -1726,8 +1726,8 @@ merge(Compressor.prototype, {
var commutativeOperators = makePredicate("== === != !== * & | ^");
OPT(AST_Binary, function(self, compressor){
function reverse(op) {
if (!(self.left.has_side_effects() || self.right.has_side_effects())) {
function reverse(op, force) {
if (force || !(self.left.has_side_effects() || self.right.has_side_effects())) {
if (op) self.operator = op;
var tmp = self.left;
self.left = self.right;
@@ -1737,7 +1737,10 @@ merge(Compressor.prototype, {
if (commutativeOperators(self.operator)) {
if (self.right instanceof AST_Constant
&& !(self.left instanceof AST_Constant)) {
reverse();
// if right is a constant, whatever side effects the
// left side might have could not influence the
// result. hence, force switch.
reverse(null, true);
}
}
self = self.lift_sequences(compressor);
@@ -1751,15 +1754,15 @@ merge(Compressor.prototype, {
// XXX: intentionally falling down to the next case
case "==":
case "!=":
if (compressor.option("unsafe")
&& self.left instanceof AST_UnaryPrefix
&& self.left.operator == "typeof"
&& self.right instanceof AST_String
&& self.right.value == "undefined") {
if (!(self.left.expression instanceof AST_SymbolRef)
|| !self.left.expression.undeclared()) {
self.left = self.left.expression;
self.right = make_node(AST_Undefined, self.left).optimize(compressor);
if (self.left instanceof AST_String
&& self.left.value == "undefined"
&& self.right instanceof AST_UnaryPrefix
&& self.right.operator == "typeof"
&& compressor.option("unsafe")) {
if (!(self.right.expression instanceof AST_SymbolRef)
|| !self.right.expression.undeclared()) {
self.right = self.right.expression;
self.left = make_node(AST_Undefined, self.left).optimize(compressor);
if (self.operator.length == 2) self.operator += "=";
}
}

13
test/compress/issue-105.js
View File

@@ -3,7 +3,7 @@ typeof_eq_undefined: {
comparisons: true
};
input: { a = typeof b.c != "undefined" }
expect: { a = typeof b.c != "undefined" }
expect: { a = "undefined" != typeof b.c }
}
typeof_eq_undefined_unsafe: {
@@ -12,5 +12,14 @@ typeof_eq_undefined_unsafe: {
unsafe: true
};
input: { a = typeof b.c != "undefined" }
expect: { a = b.c !== void 0 }
expect: { a = void 0 !== b.c }
}
typeof_eq_undefined_unsafe2: {
options = {
comparisons: true,
unsafe: true
};
input: { a = "undefined" != typeof b.c }
expect: { a = void 0 !== b.c }
}