[kevingadd]

When doing fancy things with typescript types, be really careful - it's possible to accidentally construct typescript types that will increase your tsc compile times by multiple seconds and the tooling for troubleshooting this is nonexistent. A tiny change to one codebase I work on made compile times go from 300ms to something like 7 seconds and it took me something like 14 hours of grepping and manually bisecting source code to find the cause - tsc was O(N * N * N) trying all possible types for a string literal to determine whether any of them were valid matches, and someone had defined a very fancy string literal type.

When this happens, typescript language integration (like in vs code or sublime text) will suddenly fall over and stop working correctly, and it'll be near impossible to figure that out too.

Our build uses rollup to invoke tsc and as it happens their profiling system doesn't actually measure how long tsc takes to run - the time is unaccounted :) So in general, be aware that 'typescript is taking a long time to compile' is a blind spot for this whole ecosystem and if you hit it you're going to have to work hard to fix it.

[int_19h]

This doesn't even require a type system anywhere near as fancy as what TS has. C#, for example, has a similar problem with how type inference in lambdas interacts with overload resolution, once you start nesting those lambdas:

https://docs.microsoft.com/en-us/archive/blogs/ericlippert/l...