Ensure correct type parameter of serialized RemoteChannel (#179)

When serializing RemoteChannels, a new zeroed RemoteChannel is
constructed. However, the input type parameter might be part of an outer
type parameter which can then lead to a TypeError during deserialization.
The fix is just to reuse the type parameter of the input when
constructing the zeroed RemoteChannel.

(cherry picked from commit 6649a94075ff6a52ee9558db3ec4491496bf1bea)

Author: andreasnoack

src/remotecall.jl

@@ -413,8 +413,8 @@ function serialize(s::AbstractSerializer, ::Future)
     invoke(serialize, Tuple{AbstractSerializer, Any}, s, zero_fut)
 end
 
-function serialize(s::AbstractSerializer, ::RemoteChannel)
-    zero_rc = RemoteChannel{Channel{Any}}((0,0,0))
+function serialize(s::AbstractSerializer, ::RemoteChannel{T}) where T
+    zero_rc = RemoteChannel{T}((0,0,0))
     invoke(serialize, Tuple{AbstractSerializer, Any}, s, zero_rc)
 end
 

test/distributed_exec.jl

@@ -343,9 +343,12 @@ end
 @testset "Ser/deser to non-ClusterSerializer objects" begin
     function test_regular_io_ser(ref::DistributedNext.AbstractRemoteRef)
         io = IOBuffer()
-        serialize(io, ref)
+        # Wrapping the ref in a Dict to exercise the case when the
+        # type parameter of the RemoteChannel is part of an outer type.
+        # See https://github.com/JuliaLang/Distributed.jl/issues/178
+        serialize(io, Dict("ref" => ref))
         seekstart(io)
-        ref2 = deserialize(io)
+        ref2 = deserialize(io)["ref"]
         for fld in fieldnames(typeof(ref))
             v = getfield(ref2, fld)
             if isa(v, Number)
@@ -361,6 +364,7 @@ end
 
     test_regular_io_ser(Future())
     test_regular_io_ser(RemoteChannel())
+    test_regular_io_ser(RemoteChannel(() -> Channel{Bool}(1)))
 end
 
 @testset "@distributed and [un]buffered reads" begin