Julia Crash

[rapus95]

MWE:

gradient(x->unsafe_copyto!([], 1, [], 1, 0), 1)

Well, originally I tried to use some code which built the median. Of course, deriving the median doesn't make sense. But using a non-derivable function makes Julia crash doesn't make sense either.
So I guess there should be any sort of barrier which prevents crashing without any helpful error.

Actual Error:

Assertion failed: token.V->getType()->isTokenTy(), file /cygdrive/d/buildbot/worker/package_win64/build/src/codegen.cpp, line 4345

signal (22): SIGABRT
in expression starting at REPL[11]:1
crt_sig_handler at /cygdrive/d/buildbot/worker/package_win64/build/src\signals-win.c:92
raise at C:\Windows\System32\msvcrt.dll (unknown line)
abort at C:\Windows\System32\msvcrt.dll (unknown line)
assert at C:\Windows\System32\msvcrt.dll (unknown line)
emit_expr at /cygdrive/d/buildbot/worker/package_win64/build/src\codegen.cpp:4345
emit_ssaval_assign at /cygdrive/d/buildbot/worker/package_win64/build/src\codegen.cpp:3839
emit_stmtpos at /cygdrive/d/buildbot/worker/package_win64/build/src\codegen.cpp:4032 [inlined]
emit_function at /cygdrive/d/buildbot/worker/package_win64/build/src\codegen.cpp:6658
jl_compile_linfo at /cygdrive/d/buildbot/worker/package_win64/build/src\codegen.cpp:1257
emit_invoke at /cygdrive/d/buildbot/worker/package_win64/build/src\codegen.cpp:3311
emit_expr at /cygdrive/d/buildbot/worker/package_win64/build/src\codegen.cpp:4127
emit_ssaval_assign at /cygdrive/d/buildbot/worker/package_win64/build/src\codegen.cpp:3839
emit_stmtpos at /cygdrive/d/buildbot/worker/package_win64/build/src\codegen.cpp:4032 [inlined]
emit_function at /cygdrive/d/buildbot/worker/package_win64/build/src\codegen.cpp:6658
jl_compile_linfo at /cygdrive/d/buildbot/worker/package_win64/build/src\codegen.cpp:1257
jl_compile_method_internal at /cygdrive/d/buildbot/worker/package_win64/build/src\gf.c:1889
_jl_invoke at /cygdrive/d/buildbot/worker/package_win64/build/src\gf.c:2153 [inlined]
jl_apply_generic at /cygdrive/d/buildbot/worker/package_win64/build/src\gf.c:2322
_pullback at C:\Users\Matthis\.julia\packages\Zygote\oMScO\src\compiler\interface.jl:31
pullback at C:\Users\Matthis\.julia\packages\Zygote\oMScO\src\compiler\interface.jl:37
unknown function (ip: 00000000022AD43D)
_jl_invoke at /cygdrive/d/buildbot/worker/package_win64/build/src\gf.c:2158 [inlined]
jl_apply_generic at /cygdrive/d/buildbot/worker/package_win64/build/src\gf.c:2322
jl_apply at /cygdrive/d/buildbot/worker/package_win64/build/src\julia.h:1692 [inlined]
do_apply at /cygdrive/d/buildbot/worker/package_win64/build/src\builtins.c:643
gradient at C:\Users\Matthis\.julia\packages\Zygote\oMScO\src\compiler\interface.jl:46
_jl_invoke at /cygdrive/d/buildbot/worker/package_win64/build/src\gf.c:2144 [inlined]
jl_apply_generic at /cygdrive/d/buildbot/worker/package_win64/build/src\gf.c:2322
jl_apply at /cygdrive/d/buildbot/worker/package_win64/build/src\julia.h:1692 [inlined]
do_call at /cygdrive/d/buildbot/worker/package_win64/build/src\interpreter.c:369
eval_value at /cygdrive/d/buildbot/worker/package_win64/build/src\interpreter.c:458
eval_stmt_value at /cygdrive/d/buildbot/worker/package_win64/build/src\interpreter.c:409 [inlined]
eval_body at /cygdrive/d/buildbot/worker/package_win64/build/src\interpreter.c:803
jl_interpret_toplevel_thunk at /cygdrive/d/buildbot/worker/package_win64/build/src\interpreter.c:911
jl_toplevel_eval_flex at /cygdrive/d/buildbot/worker/package_win64/build/src\toplevel.c:814
jl_toplevel_eval_flex at /cygdrive/d/buildbot/worker/package_win64/build/src\toplevel.c:764
jl_toplevel_eval at /cygdrive/d/buildbot/worker/package_win64/build/src\toplevel.c:823 [inlined]
jl_toplevel_eval_in at /cygdrive/d/buildbot/worker/package_win64/build/src\toplevel.c:843
eval at .\boot.jl:331
_jl_invoke at /cygdrive/d/buildbot/worker/package_win64/build/src\gf.c:2144 [inlined]
jl_apply_generic at /cygdrive/d/buildbot/worker/package_win64/build/src\gf.c:2322
eval_user_input at D:\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.4\REPL\src\REPL.jl:86
run_backend at C:\Users\Matthis\.julia\packages\Revise\S7mrl\src\Revise.jl:1057
#85 at .\task.jl:358
_jl_invoke at /cygdrive/d/buildbot/worker/package_win64/build/src\gf.c:2158 [inlined]
jl_apply_generic at /cygdrive/d/buildbot/worker/package_win64/build/src\gf.c:2322
jl_apply at /cygdrive/d/buildbot/worker/package_win64/build/src\julia.h:1692 [inlined]
start_task at /cygdrive/d/buildbot/worker/package_win64/build/src\task.c:687
Allocations: 140752549 (Pool: 140725293; Big: 27256); GC: 137

[CarloLucibello]

On current master I get

julia> gradient(x->unsafe_copyto!([], 1, [], 1, 0), 1)
ERROR: Output should be scalar; gradients are not defined for output Any[]
Stacktrace:
 [1] error(::String) at ./error.jl:33
 [2] sensitivity(::Array{Any,1}) at /home/carlo/.julia/packages/Zygote/XCgv1/src/compiler/interface.jl:43
 [3] gradient(::Function, ::Int64, ::Vararg{Int64,N} where N) at /home/carlo/.julia/packages/Zygote/XCgv1/src/compiler/interface.jl:47
 [4] top-level scope at REPL[4]:1

so I guess this is fine since the output from unsafe_copyto! is

julia> unsafe_copyto!([], 1, [], 1, 0)
0-element Array{Any,1}

Feel free to reopen if anything amiss