Monomorphization panic when giving a host a thunk

[rtfeldman]

To reproduce:

1. Start with examples/hello-world/Hello.roc
2. In Package-Config.roc, change { main : Str } to { main : {} -> Str }
3. In Hello.roc, change main = "Hello, World!\n" to main = \{} -> "Hello, World!\n"

This panics with '#UserApp.0 should be in the list of imported_module_thunks', compiler/mono/src/ir.rs:7143:13

[ayazhafiz]

I can't reproduce this on trunk anymore - can you? Interestingly though, running roc check (with a debug build) sometimes gives a panic:

thread 'main' panicked at 'assertion failed: state.dependencies.solved_all()', compiler/load/src/file.rs:1968:17

So I guess there's a race condition somewhere there

[folkertdev]

Richard and I discussed this earlier today (I also ran into the problem). The cause is the Effect module which is not imported by any module, but it is still scheduled for type checking. That never happens. We decided to go ahead with implementing https://github.com/rtfeldman/roc/issues/2405 and then the issue should disappear