_
   _       _ _(_)_     |  Documentation: https://docs.julialang.org
  (_)     | (_) (_)    |
   _ _   _| |_  __ _   |  Type "?" for help, "]?" for Pkg help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 1.9.0-DEV.1189 (2022-08-26)
 _/ |\__'_|_|_|\__'_|  |  Commit 293031b4a5* (0 days old master)
|__/                   |

julia> function foo(@nospecialize(a), b::Union{Vector{Any}, Float64, Nothing})
           ccall(:jl_, Cvoid, (Any,), (a, b))
       end
foo (generic function with 1 method)

julia> foo(a::Int, b::Nothing) = @invoke foo(a::Any, b)
foo (generic function with 2 methods)

julia> foo(1, nothing)
(1, nothing)

julia> function foo(@nospecialize(a), b::Union{Nothing, Float64})
           ccall(:jl_, Cvoid, (Any,), (a, b, 2))
       end
julia: /home/keno/julia/src/gf.c:1870: ijl_method_table_insert: Assertion `oldentry' failed.

[1550886] signal (6): Aborted
in expression starting at REPL[4]:1
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: 0x7fe2c5e34728)
__assert_fail at /lib/x86_64-linux-gnu/libc.so.6 (unknown line)
ijl_method_table_insert at /home/keno/julia/src/gf.c:1870
ijl_method_def at /home/keno/julia/src/method.c:1056
eval_methoddef at /home/keno/julia/src/interpreter.c:111
eval_body at /home/keno/julia/src/interpreter.c:554
jl_interpret_toplevel_thunk at /home/keno/julia/src/interpreter.c:751
jl_toplevel_eval_flex at /home/keno/julia/src/toplevel.c:912
jl_toplevel_eval_flex at /home/keno/julia/src/toplevel.c:856
ijl_toplevel_eval at /home/keno/julia/src/toplevel.c:921
ijl_toplevel_eval_in at /home/keno/julia/src/toplevel.c:971
eval at ./boot.jl:370 [inlined]
eval_user_input at /home/keno/julia/usr/share/julia/stdlib/v1.9/REPL/src/REPL.jl:152
repl_backend_loop at /home/keno/julia/usr/share/julia/stdlib/v1.9/REPL/src/REPL.jl:248
#start_repl_backend#46 at /home/keno/julia/usr/share/julia/stdlib/v1.9/REPL/src/REPL.jl:233
start_repl_backend##kw at /home/keno/julia/usr/share/julia/stdlib/v1.9/REPL/src/REPL.jl:230 [inlined]
#run_repl#59 at /home/keno/julia/usr/share/julia/stdlib/v1.9/REPL/src/REPL.jl:372
run_repl at /home/keno/julia/usr/share/julia/stdlib/v1.9/REPL/src/REPL.jl:357
jfptr_run_repl_56747 at /home/keno/julia/usr/lib/julia/sys-debug.so (unknown line)
_jl_invoke at /home/keno/julia/src/gf.c:2428
ijl_apply_generic at /home/keno/julia/src/gf.c:2629
#1007 at ./client.jl:413
jfptr_YY.1007_35886 at /home/keno/julia/usr/lib/julia/sys-debug.so (unknown line)
_jl_invoke at /home/keno/julia/src/gf.c:2428
ijl_apply_generic at /home/keno/julia/src/gf.c:2629
jl_apply at /home/keno/julia/src/julia.h:1855
jl_f__call_latest at /home/keno/julia/src/builtins.c:774
#invokelatest#2 at ./essentials.jl:804 [inlined]
invokelatest at ./essentials.jl:801 [inlined]
run_main_repl at ./client.jl:397
exec_options at ./client.jl:314
_start at ./client.jl:514
jfptr__start_42685 at /home/keno/julia/usr/lib/julia/sys-debug.so (unknown line)
_jl_invoke at /home/keno/julia/src/gf.c:2428
ijl_apply_generic at /home/keno/julia/src/gf.c:2629
jl_apply at /home/keno/julia/src/julia.h:1855
true_main at /home/keno/julia/src/jlapi.c:567
jl_repl_entrypoint at /home/keno/julia/src/jlapi.c:711
jl_load_repl at /home/keno/julia/cli/loader_lib.c:277
main at /home/keno/julia/cli/loader_exe.c:59
__libc_start_main at /lib/x86_64-linux-gnu/libc.so.6 (unknown line)
_start at ./julia (unknown line)
Allocations: 2955 (Pool: 2941; Big: 14); GC: 0
Aborted