Top Level `let`s causing EXC_BAD_ACCESS

[alexito4]

Description
I have a reproducible case of top level let declarations randomly causing crashes.
The project is a simple Swift CLI tool, using https://github.com/pointfreeco/swift-parsing .
You can find the specific branch with the problem here https://github.com/alexito4/kindle-highlights/tree/swift-crash-repo and a conversation on the swift-parsing repo pointfreeco/swift-parsing#275
I've discarded pretty much anything else I could, there is another branch trying-fixes where I removed everything I could and still crashes, albeit at different points (which to me points to some memory issue since every slight change in the program makes it crash differently)

Steps to reproduce

1. Checkout https://github.com/alexito4/kindle-highlights.git
2. Switch to the swift-crash-repo branch
3. Run swift run -c release kindle-highlights ./short.txt and see it crash with 6993 bus error ❌
4. Run (in debug) swift run kindle-highlights ./short.txt and it works fine (at least on my machine) ✅
5. You can also open Xcode xed . and run the tests, you will get a Thread 1: EXC_BAD_ACCESS ❌ Note that some tests also fail (before crashing) due to what seems some bad memory when manipulating the strings.

Expected behavior
It shouldn't crash.

Screenshots
Crash running tests trough Xcode:

Crash running with release config:

Environment

• Swift compiler version info: swift-driver version: 1.62.15 Apple Swift version 5.7.2 (swiftlang-5.7.2.135.5 clang-1400.0.29.51) Target: arm64-apple-macosx13.0
• Xcode version info: Version 14.2 (14C18)
• Deployment target: macOS 13.1 (22C65)

I've also tried running it in Docker with the same results. Docker Image swift-5.7.2 platform ubuntu22.04

Additional context
After being pointed to an issue with top level declarations pointfreeco/swift-parsing#275 (comment) I switched the code to use functions and create the parsers instead of storing them in top level lets and all the problems have gone away. (the diff is here alexito4/kindle-highlights@c82ce47)