Reserve First

https://matklad.github.io/2025/08/16/reserve-first.html

In these two cases in particular, the only source of errors is fallible allocation. And there’s a pattern to fix it:

• First, reserve enough memory for operation, without applying any changes to the data structure,
• Then, mutate the data structure in an error-free code path.

This seems to me a very similar principle to the one presented in Parse, don't validate - to perform a potentially dangerous operation, do work up front to change the environment and make errors impossible later on.