Confusing error message when calling toSeq using a non-iterator

[dawkot]

import sequtils

type A = object
iterator items(self: A): int = discard
discard toSeq(A())  #type mismatch: got (seq[A], int)

This works:

discard toSeq(A().items)

Normally "toSeq" calls the "items" iterator if it finds one on it's own.

toSeq(1..10)

[ghost]

But should it?
1..10 is actually an iterator - https://github.com/nim-lang/Nim/blob/devel/lib/system.nim#L2036, and A() is not

[dawkot]

My bad then.
Still, the error message is pretty confusing.

[timotheecour]

/cc @Yardanico @daw

• error msg would be better under this RFC: https://github.com/nim-lang/Nim/issues/8774 since toSeq would be able to use a template constraint for the untyped param
• independently of that, universal toSeq: works with UFCS; works with inline & closure iterators, and with iterables #8711 actually makes your test case work

[narimiran]

#8711 actually makes your test case work

That is now merged and this indeed works.