clone method
Implementation
@override
MixinRulesetDirective clone() {
var clonedArgs = <VarDefinition>[];
for (var arg in definedArgs) {
clonedArgs.add(arg.clone() as VarDefinition);
}
var clonedRulesets = <TreeNode>[];
for (var ruleset in rulesets) {
clonedRulesets.add(ruleset.clone());
}
return MixinRulesetDirective(
name, clonedArgs, varArgs, clonedRulesets, span);
}