Different type inferred when setting a default value for an array field

[ericvw]

Description

When setting a default value for an array field in an object where the size is as an enumeration type, attempting to iterate over the array in a for-loop yields a compiler error because it infers the type as being different than the declared type.

The code below illustrates the issue:

type
    Direction = enum
        North
        South
        East
        West

    ArrayObj1 = object
        list: array[Direction, int]

    ArrayObj2 = object
        list: array[Direction, int] = [1, 2, 3, 4]


var a: ArrayObj1
for i in Direction:
    echo a.list[i] # Compiles without issue.

var b: ArrayObj2
for i in Direction:
    echo b.list[i] # Errors that there is a type mismatch.

Nim Version

Nim Compiler Version 2.0.0 [MacOSX: amd64]
Compiled at 2023-10-05
Copyright (c) 2006-2023 by Andreas Rumpf

active boot switches: -d:release

Current Output

$ nim c test.nim
......................................................................
/Users/eric/projects/advent-of-code.git/2022/test.nim(21, 16) Error: type mismatch
Expression: `[]`(b.list, i)
  [1] b.list: array[0..3, int]
  [2] i: Direction

Expected one of (first mismatch at [position]):
[0] proc `[]`(s: string; i: BackwardsIndex): char
[0] proc `[]`(s: var string; i: BackwardsIndex): var char
[0] proc `[]`[I: Ordinal; T](a: T; i: I): T
[0] proc `[]`[Idx, T; U, V: Ordinal](a: array[Idx, T]; x: HSlice[U, V]): seq[T]
[0] proc `[]`[Idx, T](a: array[Idx, T]; i: BackwardsIndex): T
[0] proc `[]`[Idx, T](a: var array[Idx, T]; i: BackwardsIndex): var T
[0] proc `[]`[T, U: Ordinal](s: string; x: HSlice[T, U]): string
[0] proc `[]`[T; U, V: Ordinal](s: openArray[T]; x: HSlice[U, V]): seq[T]
[0] proc `[]`[T](s: openArray[T]; i: BackwardsIndex): T
[0] proc `[]`[T](s: var openArray[T]; i: BackwardsIndex): var T
[0] template `[]`(a: WideCStringObj; idx: int): Utf16Char
[0] template `[]`(s: string; i: int): char

Expected Output

The program to compile without error.

Possible Solution

No response

Additional Information

No response

[beef331]

Just for a workaround:

type
    Direction = enum
        North
        South
        East
        West

    ArrayObj1 = object
        list: array[Direction, int]

    ArrayObj2 = object
        list: array[Direction, int] = [North: 1, 2, 3, 4]


var a: ArrayObj1
for i in Direction:
    echo a.list[i]

var b: ArrayObj2
for i in Direction:
    echo b.list[i]

[ericvw]

Thanks for the workaround, @beef331. I'll use that for the time being.