Size as an immediate in array.new_fixed

[patrick96]

It looks like the parser used in wasm-as does not support providing the size of the array in the array.new_fixed instruction as an immediate value. Is that intentional?

From what I can tell from the GC MVP document, an immediate value is required as part of the instruction. Their test suite seems to confirm this:

https://github.com/WebAssembly/gc/blob/099b55020af2ac29fb6f2886581de057d7372b02/test/core/gc/array.wast#L112-L114

I just wanted to first check whether there is a reason for this. I'm happy to open up a proper bug report if anyone thinks this should be looked into.

[kripken]

Yes, this looks like a bug in our text parsing and emitting. Binaryen IR is structured so the immediate is not strictly needed in theory, but we should add it to follow the spec.

[kripken]

I created #5769 to track this.