Function UnwrapExpressionUntil

expr_unwrap.go:57–71

UnwrapExpressionUntil is similar to UnwrapExpression except it gives the caller an opportunity to test each level of unwrapping to see each a particular expression is accepted. This could be used, for example, to unwrap until a particular other interface is satisfied, regardless of wrap wrapping le

(expr Expression, until func(Expression) bool)

// function rejects even the final, physical expression then the result of
// this function is nil.
func UnwrapExpressionUntil(expr Expression, until func(Expression) bool) Expression {
	for {
		if until(expr) {
			return expr
		}
		unwrap, wrapped := expr.(unwrapExpression)
		if !wrapped {
			return nil
		}
		expr = unwrap.UnwrapExpression()
		if expr == nil {
			return nil
		}
	}
}