fix: wait for iterAsync through ForEachAsync instead of CountAsync

CHANGELOG.md

@@ -31,6 +31,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - `rxquery` emitted its elements on the thread pool, out of order and after the source had moved on; `yield` and `zero` are now synchronous
 - `rxquery` `sumBy` passed `null` to the `(+)` of reference types
 - A positional comparer or element selector passed to the `Async` `toLookup` was silently ignored
+- `iterAsync` could fault with `OverflowException` on sources with more than `Int32.MaxValue` elements
 - `chunkBy` accepted a non-positive window length of `ChunkTimeSpanCount` and `ChunkMillisecondsCount`, which failed every element
 - Misleading XML docs of `catch`
 

src/FSharp.Control.R3/AsyncObservable.fs

@@ -144,7 +144,9 @@ module Observable =
     /// by intercepting the message stream to run arbitrary actions for messages on the pipeline.
     /// </remarks>
     /// <exception cref="T:System.ArgumentOutOfRangeException">Thrown when the concurrency limit of the options is 0 or below -1.</exception>
-    let iterAsync options (action : 't -> Async<unit>) source = source |> mapAsync options action |> length |> Async.Ignore
+    let iterAsync options (action : 't -> Async<unit>) source =
+        // Waits through iter: waiting through length counted the elements with a checked add, which overflows on long-lived sources
+        source |> mapAsync options action |> iter ignore
 
 [<AutoOpen>]
 module Extensions =

src/FSharp.Control.R3/TaskObservable.fs

@@ -61,10 +61,10 @@ module Observable =
     /// </remarks>
     /// <exception cref="T:System.ArgumentOutOfRangeException">Thrown when the concurrency limit of the options is 0 or below -1.</exception>
     let iterAsync cancellationToken options (action : CancellationToken -> 't -> Task<unit>) source =
+        // Waits through iter: waiting through length counted the elements with a checked add, which overflows on long-lived sources
         source
         |> mapAsync options action
-        |> length cancellationToken
-        :> Task
+        |> iter cancellationToken ignore
 
 [<AutoOpen>]
 module Extensions =