Migration to v2

[ringabout]

Cannot cast ref to RootRef in Arc/Orc

affected important packages:

• https://github.com/yglukhov/nimsl cannot cast ref to RootRef in Arc/Orc #20016

Solution

type
  Color = ref object

var x = Color()
let y = cast[pointer](x)
# use Gc_ref(y) when it is needed

shallowCopy/shallow

• https://github.com/andreaferretti/cello shallowcopy string doesn't work with arc/orc #20015

Solution

shallowCopy/shallow becomes a compile-time error with ARC/ORC. move seqs/strings instead.

proc main()
  var x = "123"
  var y = move(x)

You can also use sink to let the compiler decide whether to move the data or copy the data.

proc main(x: sink string) =
  var y = x

Another solution is to use {.cursor.}.

deepcopy

• https://github.com/def-/nim-iterutils/pull/15
• enable deepcopy for tests moigagoo/norm#155

Solution

Enable deepcopy for ARC/ORC. Use --deepcopy:on. Note that the option appears since 1.4.0 and it is ignored with refc.

cannot bind another destructor to ref object

#19231

affected important packages:

• https://github.com/Vladar4/nimgame2

minimal testcase

type
  A = ref object

var x1: A
new(x1, proc (x: A) {.nimcall.} = discard)
var x2: A
new(x2, func (x: A) {.nimcall.} = discard)

{.global.} pragma doesn't work when the variable is initialized with non-value types

#17552

Solution

None

threadpool doesn't work with ORC

Solution

Switch to https://github.com/status-im/nim-taskpools or use createThreads.

Mixing declarations and statements at the top level causes undefined behaviour

#19795

affected important packages:

• https://github.com/zero-functional/zero-functional

Solution

None.

Workaround: move the top level statements to the main procs.

defaults to ORC

#19972

stricteffects

experimental:stricteffects is enabled for v2. There is a switch --legacy:laxeffects to keep backwards compatibility with old behaviors.

ref #19303
ref nim-lang/RFCs#435

[exelotl]

Hey, is this the right place to report that programs using nimPNG don't compile on devel?

shallowCopy usage:
https://github.com/jangko/nimPNG/blob/master/nimPNG/buffer.nim

[ringabout]

Hey, is this the right place to report that programs using nimPNG don't compile on devel?

I think you probably need to open an issue on the issue track of nimPNG and link this issue. sink parameters seems to be good enough.