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fix cascade & collapse on property access of constants (#2158)

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This commit is contained in:
Alex Lam S.L
2017-06-24 21:30:06 +08:00
committed by GitHub
parent 94e5e00c03
commit 9db4c42380
2 changed files with 115 additions and 1 deletions
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22
lib/compress.js
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@@ -547,8 +547,25 @@ merge(Compressor.prototype, {
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) {
return lhs instanceof AST_SymbolRef && lhs.definition().orig[0] instanceof AST_SymbolLambda;
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 instanceof AST_RegExp) return false;
if (lhs instanceof AST_Constant) return true;
return is_lhs_read_only(lhs);
}
return false;
}
function find_variable(compressor, name) {
@@ -1287,6 +1304,7 @@ merge(Compressor.prototype, {
def(AST_SymbolRef, function(pure_getters) {
if (this.is_undefined) return true;
if (!is_strict(pure_getters)) return false;
if (this.is_immutable()) return false;
var fixed = this.fixed_value();
return !fixed || fixed._throw_on_access(pure_getters);
});
@@ -3359,6 +3377,8 @@ merge(Compressor.prototype, {
|| cdr instanceof AST_PropAccess
|| cdr instanceof AST_Unary && !unary_side_effects(cdr.operator)) {
field = "expression";
} else if (cdr instanceof AST_Conditional) {
field = "condition";
} else {
expressions[++i] = expressions[j];
break;