expressions/lookup.js
function(key, root, sourceText) {
	this.key = key;
	this.rootExpr = root;
	canReflect.setKeyValue(this, sourceTextSymbol, sourceText);
}
function(key, root, sourceText) {
	this.key = key;
	this.rootExpr = root;
	canReflect.setKeyValue(this, sourceTextSymbol, sourceText);
}
### Lookup `new Lookup(String, [Expression])` Finds a value in the scope or a helper.