range is not a valid generic parameter type, while not range is

[PhilippMDoerner]

Description

Given how almost everything in nim can be used as a generic parameter type (e.g. distinct) I would have assumed that this also holds true for range to make a generic proc for any range type.

However, this is not possible.

proc isRange(r: range) = echo "is range" can not compile.

Thus this code-snippet can not compile:

proc isRange(r: range) = echo "is range"
let y: 1..10 = 5
y.isRange()

Nim Version

Nim Compiler Version 2.0.0 [Linux: amd64]
Compiled at 2023-08-01
Copyright (c) 2006-2023 by Andreas Rumpf

git hash: a488067
active boot switches: -d:release

Current Output

Error: invalid type: 'range' in this context: 'proc (r: range)' for proc

Expected Output

No compiler error

Possible Solution

I only have a temporary solution for anyone running into this:
You can use a concept (Thanks to ElegantBeef for the suggestion!)

type Range = concept r
  r is range
proc isRange(r: Range) = echo "is range"
let y: range[0..10] = 5
y.isRange()

Additional Information

I am not 100% certain if this is actually a bug or me not having deep enough an understanding of typeclasses etc.
I currently assume it is a bug, because inverse of range (not range) somehow does act as a valid generic parameter type.

proc isRange(r: not range) = echo "is not range"
let y = 5
y.isRange()

This further solidified my assumption that proc isRange(r: range) should be possible.

Also this may be related to #17423 ?
I don't fully understand it but very distantly the issue seems maybe similar enough?

[metagn]

Works with [T: range](r: T). Likely range by itself is erroneously considered a concrete type and not lifted to implicit generic

[PhilippMDoerner]

Sadly that is only a solution as long as you don't define a version of that with auto.

proc isRange[T: range](r: T) = echo "is range"
proc isRange(r: auto) = echo "is not range"
let y: 1..10 = 5
y.isRange()

This for example will run into

 Error: ambiguous call; both playground.isRange(r: T: range) [proc declared in /home/philipp/dev/playground/src/playground.nim(1, 6)] and playground.isRange(r: GenericParam) [proc declared in /home/philipp/dev/playground/src/playground.nim(2, 6)] match for: (range 1..10(int))

Same for

proc isRange[T: range](r: T) = echo "is range"
proc isRange[T](r: T) = echo "is not range"
let y: 1..10 = 5
y.isRange()