I ran into my first infinite recursion error when attempting to open shell.nix, and --show-trace points to line 1, column 13:
https://gist.github.com/heath/40b04df97f7badc798a208c2a30b8cd3
There are no other nix files in the project.
Any pro tips on addressing this issue? 
What do you mean by open? The file looks completely fine to me and running nix-shell in directory with shell.nix seems to work as well.
Thanks for mentioning that it works on your machine. The error is surprising since it has been working fine on a Macbook Pro 2018 (macOS Catalina 10.15). The infinite recursion error occurs when I try running it on a different Macbook Pro (2020) with macOS Catalina 10.15.7.
By open I mean running nix-shell.
I’ll chalk it up to work laptop configurations out of my control and move on.
Do you have a ~/.config/nixpkgs/overlay{.nix,/default.nix}? Or perhaps an overlay on the system level?
Overlays are exactly that kind of impurities that might cause such irreproducible errors.