Julia: Unreachable reached

[saschatimme]

I hit a bug very similar to #30122. Unfortunately I was not able to reduce this to a self-contained example. This is on the release-1.1 branch.

              _
   _       _ _(_)_     |  Documentation: https://docs.julialang.org
  (_)     | (_) (_)    |
   _ _   _| |_  __ _   |  Type "?" for help, "]?" for Pkg help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 1.1.0-DEV.839 (2018-12-07)
 _/ |\__'_|_|_|\__'_|  |  Commit b55b85cd99 (3 days old master)
|__/                   |

julia> versioninfo()
Julia Version 1.1.0-DEV.839
Commit b55b85cd99 (2018-12-07 17:20 UTC)
Platform Info:
  OS: macOS (x86_64-apple-darwin18.0.0)
  CPU: Intel(R) Core(TM) i5-7500 CPU @ 3.40GHz
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-6.0.1 (ORCJIT, skylake)
Environment:
  JULIA_NUM_THREADS = 4

julia> using DynamicPolynomials
[ Info: Precompiling DynamicPolynomials [7c1d4256-1411-5781-91ec-d7bc3513ac07]

julia> @polyvar x[1:2]
Unreachable reached at 0x12a28a3ca

signal (4): Illegal instruction: 4
in expression starting at no file:0
setindex! at ./array.jl:764
collect_to_with_first! at ./array.jl:626
collect at ./array.jl:608
map at ./abstractarray.jl:2044 [inlined]
polyarrayvar at /Users/sascha/.julia/packages/DynamicPolynomials/3rBvr/src/var.jl:6
unknown function (ip: 0x12a28a37d)
jl_fptr_trampoline at /Users/sascha/coding/julia/src/gf.c:1854
do_call at /Users/sascha/coding/julia/src/interpreter.c:323
eval_stmt_value at /Users/sascha/coding/julia/src/interpreter.c:362 [inlined]
eval_body at /Users/sascha/coding/julia/src/interpreter.c:759
jl_interpret_toplevel_thunk_callback at /Users/sascha/coding/julia/src/interpreter.c:885
unknown function (ip: 0xfffffffffffffffe)
unknown function (ip: 0x117da000f)
unknown function (ip: 0x1)
jl_interpret_toplevel_thunk at /Users/sascha/coding/julia/src/interpreter.c:894
jl_toplevel_eval_flex at /Users/sascha/coding/julia/src/toplevel.c:764
jl_toplevel_eval at /Users/sascha/coding/julia/src/toplevel.c:773 [inlined]
jl_toplevel_eval_in at /Users/sascha/coding/julia/src/toplevel.c:793
eval at ./boot.jl:328
eval_user_input at /Users/sascha/coding/julia/usr/share/julia/stdlib/v1.1/REPL/src/REPL.jl:85
macro expansion at /Users/sascha/coding/julia/usr/share/julia/stdlib/v1.1/REPL/src/REPL.jl:117 [inlined]
#26 at ./task.jl:259
jl_apply at /Users/sascha/coding/julia/src/./julia.h:1571 [inlined]
start_task at /Users/sascha/coding/julia/src/task.c:572
Allocations: 12189244 (Pool: 12186847; Big: 2397); GC: 26
Illegal instruction: 4

[maleadt]

Can reproduce on release-1.1, assertion that is hit: julia: /home/tbesard/Julia/julia-dev/src/gf.c:1200: int check_ambiguous_visitor(jl_typemap_entry_t *, struct typemap_intersection_env *): Assertion `!jl_subtype((jl_value_t*)sig, (jl_value_t*)type)' failed.
EDIT: also on master, so not resolved (https://github.com/JuliaAlgebra/DynamicPolynomials.jl/issues/38#issuecomment-446157080)

[maleadt]

Reduced:

   _       _ _(_)_     |  Documentation: https://docs.julialang.org
  (_)     | (_) (_)    |
   _ _   _| |_  __ _   |  Type "?" for help, "]?" for Pkg help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 1.1.0-DEV.854 (2018-12-11)
 _/ |\__'_|_|_|\__'_|  |  Commit 0d620001c2* (0 days old master)
|__/                   |

julia> module Foo
       abstract type A end
       abstract type B end
       Base.convert(::Type{T}, ::A) where T<:B = nothing
       Base.convert(::Type{<:Union{Number, T}}, ::A) where T = nothing
       end
julia: /home/tbesard/Julia/julia-dev/src/gf.c:1200: int check_ambiguous_visitor(jl_typemap_entry_t *, struct typemap_intersection_env *): Assertion `!jl_subtype((jl_value_t*)sig, (jl_value_t*)type)' failed.

signal (6): Aborted
in expression starting at no file:5
gsignal at /lib/x86_64-linux-gnu/libc.so.6 (unknown line)
abort at /lib/x86_64-linux-gnu/libc.so.6 (unknown line)
unknown function (ip: 0x7f5622411a89)
__assert_fail at /lib/x86_64-linux-gnu/libc.so.6 (unknown line)
check_ambiguous_visitor at /home/tbesard/Julia/julia-dev/src/gf.c:1200
jl_typemap_intersection_node_visitor at /home/tbesard/Julia/julia-dev/src/typemap.c:0
jl_typemap_intersection_visitor at /home/tbesard/Julia/julia-dev/src/typemap.c:553
jl_typemap_intersection_visitor at /home/tbesard/Julia/julia-dev/src/typemap.c:544
check_ambiguous_matches at /home/tbesard/Julia/julia-dev/src/gf.c:1287
jl_method_table_insert at /home/tbesard/Julia/julia-dev/src/gf.c:1565
jl_method_def at /home/tbesard/Julia/julia-dev/src/method.c:800
eval_methoddef at /home/tbesard/Julia/julia-dev/src/interpreter.c:309
eval_body at /home/tbesard/Julia/julia-dev/src/interpreter.c:732
jl_interpret_toplevel_thunk_callback at /home/tbesard/Julia/julia-dev/src/interpreter.c:885
unknown function (ip: 0xfffffffffffffffe)
unknown function (ip: 0x7f5615caae4f)
unknown function (ip: 0xa)
jl_interpret_toplevel_thunk at /home/tbesard/Julia/julia-dev/src/interpreter.c:894
jl_toplevel_eval_flex at /home/tbesard/Julia/julia-dev/src/toplevel.c:764
jl_eval_module_expr at /home/tbesard/Julia/julia-dev/src/toplevel.c:179
jl_toplevel_eval_flex at /home/tbesard/Julia/julia-dev/src/toplevel.c:614
jl_toplevel_eval at /home/tbesard/Julia/julia-dev/src/toplevel.c:773 [inlined]
jl_toplevel_eval_in at /home/tbesard/Julia/julia-dev/src/toplevel.c:793
eval at ./boot.jl:328
jl_apply_generic at /home/tbesard/Julia/julia-dev/src/gf.c:2209
eval_user_input at /home/tbesard/Julia/julia-dev/build/release/usr/share/julia/stdlib/v1.1/REPL/src/REPL.jl:85
macro expansion at /home/tbesard/Julia/julia-dev/build/release/usr/share/julia/stdlib/v1.1/REPL/src/REPL.jl:117 [inlined]
#26 at ./task.jl:259
jl_fptr_trampoline at /home/tbesard/Julia/julia-dev/src/gf.c:1854
jl_apply_generic at /home/tbesard/Julia/julia-dev/src/gf.c:2209
jl_apply at /home/tbesard/Julia/julia-dev/src/julia.h:1571 [inlined]
start_task at /home/tbesard/Julia/julia-dev/src/task.c:572
unknown function (ip: 0xffffffffffffffff)
Allocations: 11775953 (Pool: 11773673; Big: 2280); GC: 25
zsh: abort      ./julia

[JeffBezanson]

The assertion failure is not necessarily related.

[JeffBezanson]

Ah, it looks like in this case it is, since the compiler and runtime seem to disagree on whether there is an ambiguity error.