Ensure correct type parameter of serialized RemoteChannel (#179)

This is a forward-port of
JuliaLang/Distributed.jl#179
(JuliaLang/Distributed.jl@6649a94).

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)
(cherry picked from commit 2e52996)

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