new-styled concepts: type mismatch for function implemented for other generic concept #24742
Description
Nim Version
Nim Compiler Version 2.2.2 [Linux: amd64]
Linux 6.6.56, NixOS 24.11
Description
I'm attempting to define a concept using a function implemented for another generic concept.
The following example compiles with old-styled concepts, but fails with new-styled concepts:
test.nim:
type Indexable[T] = concept
proc `[]`(t: Self, i: int): T
proc len(t: Self): int
iterator items[T](t: Indexable[T]): T =
for i in 0 ..< t.len:
yield t[i]
# With new-styled concepts: type mismatch
type Enumerable[T] = concept
iterator items(t: Self): T
# With old-styled concepts: works
# type Enumerable[T] = concept c
# items(c) is T
proc echoAll[T](t: Enumerable[T]) =
for item in t:
echo item
type DummyIndexable[T] = distinct seq[T]
proc `[]`[T](t: DummyIndexable[T], i: int): T =
seq[T](t)[i]
proc len[T](t: DummyIndexable[T]): int =
seq[T](t).len
let dummyIndexable = DummyIndexable(@[1, 2])
echoAll(dummyIndexable)Current Output
test.nim(33, 8) Error: type mismatch
Expression: echoAll(dummyIndexable)
[1] dummyIndexable: DummyIndexable[system.int]
Expected one of (first mismatch at [position]):
[1] proc echoAll[T](t: Enumerable[T])
Expected Output
1
2
Known Workarounds
Using old-styled concepts (as commented in the example snippet) works.
Additional Information
No response