wasm-opt: Fatal: invalid type: distinct rec groups would be identical after binary writing at index 287

[Quafadas]

This is a "vibe-coded", small scala-js project which compiles to WASM.

https://github.com/Quafadas/boid

Assuming, that it is not desirable to go through the hassle of setting up scala-cli etc to build, it, I've uploaded a zip of the wasm it emits.

target.zip

And at which I randomly decided to point wasm-opt at the wasm module it emits. That yielded the below.

simon@Simons-Mini-2 boid % wasm-opt /Users/simon/Code/boid/target/main.wasm -o arg.wasm
Fatal: invalid type: distinct rec groups would be identical after binary writing at index 287

My experience with the binaryen toolchain is very limited. I do not consider myself a confident operator of it, but I'm told this isn't supposed to happen... The error message itself, does not offer a hint as to whether there is a user-land solution, so whilst I'm not confident about exactly what I'm reporting, I hope that it does clear a threshold for reporting somthing, as the wasm appears useable, but wasm-opt doesn't like it.

Note: this ticket written by actual human.

[kripken]

I don't see an error on latest main. Perhaps this has been fixed and you tested an older version?

[Quafadas]

Oh, curious - thankyou for looking - sounds like good news... for posterity I checked my version

simon@Simons-Mini-2 cwazy % wasm-opt --version
wasm-opt version 128

I'll close this and keep an eye out for 129 against the assumption it's a recent fix.

Will re-open if the issue survives the next release...

[kripken]

Oh wait, I noticed your command has no feature flags on it. I was running it with -all. That is the actual issue here. I can reproduce it that way,

$ bin/wasm-opt main.wasm 
Fatal: invalid type: distinct rec groups would be identical after binary writing at index 287
$ bin/wasm-opt main.wasm -all
[..no error..]

@tlively it is unfortunate that the distinct rec groups would be identical after binary writing error shows up rather than "you need to enable the GC flag" error. Can we fix that?

[kripken]

Reduced testcase:

(module
 (type $0 (func (param anyref) (result i32)))
 (type $1 (func (param (ref any)) (result i32)))
 (func $0 (param $0 anyref) (result i32)
  (unreachable)
 )
 (func $1 (param $0 (ref any)) (result i32)
  (unreachable)
 )
)

[Quafadas]

Just to confirm that for me too;

simon@Simons-Mini-2 boid % wasm-opt /Users/simon/Code/boid/target/main.wasm -o /Users/simon/Code/boid/target/main.min.wasm -all -O2

Is apparently successful, so it appears as though it's simply a case of getting the right flags in play and it looks as though there's already a PR to improve the error message. Fast work. Thankyou, for the hints.