Generic function works in module but importing it fails

[oakes]

The following code works:

import sets, sequtils

proc dedupe*[T](arr: openArray[T]): seq[T] =
  arr.toHashSet.toSeq

echo dedupe([1, 2, 3])

But if I move the proc to its own module, named foo, and try to import it like this...

import foo

echo dedupe([1, 2, 3])

I get this error:

nim_misc.nim(3, 12) template/generic instantiation of `dedupe` from here
nim_misc/src/foo.nim(4, 6) Error: type mismatch: got <HashSet[system.int]>
but expected one of: 
iterator items(E: typedesc[enum]): E:type
  first type mismatch at position: 1
  required type for E: type enum
  but expression 'toHashSet(arr)' is of type: HashSet[system.int]
iterator items(a: cstring): char
  first type mismatch at position: 1
  required type for a: cstring
  but expression 'toHashSet(arr)' is of type: HashSet[system.int]
iterator items(a: string): char
  first type mismatch at position: 1
  required type for a: string
  but expression 'toHashSet(arr)' is of type: HashSet[system.int]
iterator items[IX, T](a: array[IX, T]): T
  first type mismatch at position: 1
  required type for a: array[IX, T]
  but expression 'toHashSet(arr)' is of type: HashSet[system.int]
iterator items[T: char](a: openArray[T]): T
  first type mismatch at position: 1
  required type for a: openArray[T: char]
  but expression 'toHashSet(arr)' is of type: HashSet[system.int]
iterator items[T: not char](a: openArray[T]): lent2 T
  first type mismatch at position: 1
  required type for a: openArray[T: not char]
  but expression 'toHashSet(arr)' is of type: HashSet[system.int]
iterator items[T](a: seq[T]): lent2 T
  first type mismatch at position: 1
  required type for a: seq[T]
  but expression 'toHashSet(arr)' is of type: HashSet[system.int]
iterator items[T](a: set[T]): T
  first type mismatch at position: 1
  required type for a: set[T]
  but expression 'toHashSet(arr)' is of type: HashSet[system.int]
iterator items[T](s: HSlice[T, T]): T
  first type mismatch at position: 1
  required type for s: HSlice[items.T, items.T]
  but expression 'toHashSet(arr)' is of type: HashSet[system.int]

Expected Output

The import should work without error.

Possible Solution

• If you put import sets before the import foo, it works.
• In the foo module, if you do export sets.items it works.
• If you make dedupe a non-generic function (declaring it as proc dedupe*(arr: openArray[int]): seq[int] for example) it works.

Additional Information

$ nim -v
Nim Compiler Version 1.4.2 [MacOSX: amd64]
Compiled at 2020-12-21
Copyright (c) 2006-2020 by Andreas Rumpf

active boot switches: -d:release

[Clyybber]

Duplicate of #11167