Type not preserved when serialising subarrays

[MikeInnes]

julia> function roundtrip(x)
         data = IOBuffer()
         serialize(data, x)
         deserialize(IOBuffer(takebuf_array(data)))
       end

julia> xs = slice([1:10;], 1:3)
3-element SubArray{Int64,1,Array{Int64,1},Tuple{UnitRange{Int64}},1}:
 1
 2
 3

julia> type Foo{T} x::T end

julia> roundtrip(Foo(xs))
Foo{SubArray{Int64,1,Array{Int64,1},Tuple{UnitRange{Int64}},1}}([1,2,3])

julia> ans.x
3-element Array{Int64,1}:
 1
 2
 3

julia> f.x = f.x # Throws a type error

This behaviour is explicitly defined here so perhaps it's fully intentional, but it seems pretty fishy that you can create a Foo{T} type that doesn't actually contain a T. Is this really ok?

[MikeInnes]

julia> f = roundtrip(Foo(slice([1:10;], 1:3)))

julia> foo(f::Foo) = f.x[1]
foo (generic function with 1 method)

julia> foo(f)

signal (11): Segmentation fault: 11
jl_is_type at /Users/mike/julia/src/jltypes.c:68
jl_inst_concrete_tupletype_v at /Users/mike/julia/src/jltypes.c:2185
arg_type_tuple at /Users/mike/julia/src/gf.c:1407
jl_apply_generic at /Users/mike/julia/src/gf.c:1900
showerror at replutil.jl:67
showerror at replutil.jl:100
julia_showerror_23535 at  (unknown line)
jlcall_showerror_23535 at  (unknown line)
jl_apply at /Users/mike/julia/src/./julia.h:1410
anonymous at REPL.jl:101
with_output_color at util.jl:313
display_error at REPL.jl:99
jl_apply at /Users/mike/julia/src/./julia.h:1410
print_response at REPL.jl:127
jlcall_print_response_23376 at  (unknown line)
jl_apply at /Users/mike/julia/src/./julia.h:1410
print_response at REPL.jl:121
jlcall_print_response_23375 at  (unknown line)
jl_apply at /Users/mike/julia/src/./julia.h:1410
anonymous at REPL.jl:624
run_interface at ./LineEdit.jl:1610
jlcall_run_interface_18971 at /Users/mike/julia/usr/lib/julia/sys.dylib (unknown line)
jl_apply at /Users/mike/julia/src/./julia.h:1410
run_frontend at ./REPL.jl:865
run_repl at ./REPL.jl:168
jl_apply at /Users/mike/julia/src/./julia.h:1410
_start at ./client.jl:419
jlcall__start_19685 at /Users/mike/julia/usr/lib/julia/sys.dylib (unknown line)
jl_apply at /Users/mike/julia/src/./julia.h:1410
true_main at /usr/local/bin/julia (unknown line)
main at /usr/local/bin/julia (unknown line)
Segmentation fault: 11

[timholy]

Ugh. Pretty dicey behavior, and something better would be great. Presumably, creating a new view of the same type but with a different parent array would be the easiest way to fix this.

The reason for the current behavior is this: let's say you make a 10-element view from an array with 10^8 elements. If you're serializing the view, chances are good you probably don't want to serialize the entire parent array.

[kshyatt]

The segfault seems to be gone. Reopen if this is still nutty.

[mbauman]

Yup, was fixed by #14625 (which has tests).