`asyncmap!` encounters `InvalidStateException: Channel is closed`

[kaandocal]

This might be related to #35379. MWE:

output = []
asyncmap!(identity, output, 1:20)

This gives the following output:

ERROR: InvalidStateException: Channel is closed.
Stacktrace:
 [1] check_channel_state
   @ ./channels.jl:174 [inlined]
 [2] put!(c::Channel{Any}, v::Tuple{Int64, Tuple{Int64}})
   @ Base ./channels.jl:319
 [3] iterate(itr::Base.AsyncCollector, state::Base.AsyncCollectorState)
   @ Base ./asyncmap.jl:335
 [4] foreach
   @ ./abstractarray.jl:2774 [inlined]
 [5] #asyncmap!#954
   @ ./asyncmap.jl:405 [inlined]
 [6] asyncmap!(::Function, ::Vector{Any}, ::UnitRange{Int64})
   @ Base ./asyncmap.jl:404
 [7] top-level scope
   @ REPL[1]:1

Using asyncmap works fine. The error message is quite cryptic and does not explain the underlying problem (a mismatch between array sizes). In comparison, map! does not throw an error with the above code (it does not do anything).

[kaandocal]

Just as an addendum, I seem to get this error each time an exception is thrown in the inner function, and the original error does not show. Is this expected behaviour? Again here asyncmap does not suppress the original error message.

[vtjnash]

A channel can be close with a particular exception, in order to propagate an error, rather than just the generic 'Channel is closed.' message. It is likely it does not do that however, given the behavior you observed. Fixes welcome.