Vector indexing not working from REPL about luau HOT 6 CLOSED

Vectors need to implement the __index meta method that supports xyz

from luau.

This is using the built-in vector from master.

Isn't it strange that these work:

a = vec(1, 2, 3); print(a.x)  -- prints 1

a = vec(1, 2, 3)
a["x"] -- prints 1

But this doesn't?

a = vec(1, 2, 3)
a.x -- error: attempt to index vector with 'x'

(both examples work correctly when running a file, but not from REPL)

from luau.

No, that's expected. You must define an __index in the metatable, the VM bypass is just an optimization. If you don't define it other cases when the indexing code doesn't use the interpreter won't work eg v["x"..""]

from luau.

Maybe there's an argument for adding this bypass to luaV_gettable so that you can use vectors without defining a metatable; unsure if any other corners like this exist atm.

from luau.

Ah, okay. So there's a slow path and fast path for vector indexing even with built-in vectors. I'll have to make sure we always stay on the fast path. Thanks!

from luau.

Maybe there's an argument for adding this bypass to luaV_gettable so that you can use vectors without defining a metatable; unsure if any other corners like this exist atm.

I've just hit this, and I would support adding the in the bypass to luaV_gettable. It feels quite unintuitive that GETTABLEKS yields a different result compared to GETTABLE.

from luau.