SIGSEGV when returning and initializing Result in one statement when openArray and generics are involved

[etan-status]

import results

type X[flag: static bool] = object
  l: int

func init(
    T: typedesc[X],
    a: openArray[int]): Opt[X[false]] =
  ok X[false](l: a.len)

echo $X.init([1,3,3,7])

% nim -v
Nim Compiler Version 2.0.14 [MacOSX: arm64]
Compiled at 2025-01-06
Copyright (c) 2006-2023 by Andreas Rumpf

git hash: bf4de6a394e040d9810cba8c69fb2829ff04dcc6
active boot switches: -d:release

SIGSEGV: Illegal storage access. (Attempt to read from nil?)
zsh: segmentation fault  nim c -r test

It works fine when doing ok on a separate line:

import results

type X[flag: static bool] = object
  l: int

func init(
    T: typedesc[X],
    a: openArray[int]): Opt[X[false]] =
  let res = X[false](l: a.len)
  ok res

echo $X.init([1,3,3,7])

It also works fine when using std/options instead of results:

import std/options

type X[flag: static bool] = object
  l: int

func init(
    T: typedesc[X],
    a: openArray[int]): Option[X[false]] =
  some X[false](l: a.len)

echo $X.init([1,3,3,7])

It's broken on both refc and orc --mms.

[etan-status]

Possibly related: https://github.com/etan-status/eth-light/blob/14565506b8f1ce45db140c162df85fa240d59842/UpdateWasm#L33

I needed the same fix to workaround some memory corruption in wasm.

Maybe a lent bug.

[etan-status]

• Compile-time SIGSEGV with template y(): V[false] = V[false](l: 0) nim-lang/Nim#24631

ty @tersec