rust-port

1# Rust port
2 
3The goal is the Rust a Rust developer would have written to solve the same problem, with
4the same observable behavior. A line-by-line transliteration (C written in Rust syntax,
5or Python with `Box<dyn Any>`) compiles but keeps every problem the original had and adds
6the borrow checker on top. Port the behavior, not the structure.
7 
8## 1. Understand the original before writing anything
9 
101. **Read the code and its tests**, and anything that calls it, if you have it.
112. **List the observable behavior**: every public function, its inputs, its outputs, and
12   every way it can fail. Include the quiet parts, which are where ports go wrong:
13   ordering of results, how ties break, what happens on empty input, whitespace and case
14   handling, integer limits, and what counts as an error versus a valid edge case.
153. **Note what is incidental**, meaning things the original only does because of its
16   language: manual memory management, out-parameters, `NULL` returns, global state,
17   fixed-size buffers, a class that exists only to group functions, or `isinstance`
18   checks. These don't carry over.
194. If the original has a bug or an ambiguity, keep its behavior, flag it in the porting
20   notes, and let the user decide. A port is not the place to silently fix things.
21 
22## 2. Port the tests first
23 
24Translate the original tests into Rust tests before porting the implementation. Keep one
25Rust test per original test, with a name that maps back to it, so a reader can check
26…