Error when trying to showerror: TypeError: in specializations, expected DataType, got Type{Union{}}

I got the following error. It looks like it's an error with the debugger itself, that happened when it was trying to show an error with my program.

ERROR: TypeError: in specializations, expected DataType, got Type{Union{}}
Stacktrace:
  [1] #specialize_method#317
    @ ./compiler/utilities.jl:224 [inlined]
  [2] specialize_method
    @ ./compiler/utilities.jl:212 [inlined]
  [3] Base.StackTraces.StackFrame(frame::JuliaInterpreter.Frame)
    @ JuliaInterpreter ~/.julia/packages/JuliaInterpreter/ZNccU/src/utils.jl:773
  [4] show_backtrace(io::IOContext{IOBuffer}, frame::JuliaInterpreter.Frame)
    @ JuliaInterpreter ~/.julia/packages/JuliaInterpreter/ZNccU/src/utils.jl:792
  [5] showerror(io::IOContext{IOBuffer}, ex::TypeError, bt::JuliaInterpreter.Frame; backtrace::Bool)
    @ Base ./errorshow.jl:99
  [6] showerror
    @ ./errorshow.jl:95 [inlined]
  [7] display_error(io::IOContext{IOBuffer}, er::TypeError, frame::JuliaInterpreter.Frame)
    @ JuliaInterpreter ~/.julia/packages/JuliaInterpreter/ZNccU/src/utils.jl:808
  [8] (::Debugger.var"#10#19"{REPL.LineEdit.Prompt, Debugger.DebuggerState})(s::REPL.LineEdit.MIState, buf::IOBuffer, ok::Bool)
    @ Debugger ~/.julia/packages/Debugger/wueAn/src/repl.jl:72
  [9] #invokelatest#2
    @ ./essentials.jl:1055 [inlined]
 [10] invokelatest
    @ ./essentials.jl:1052 [inlined]
 [11] run_interface(terminal::REPL.Terminals.TextTerminal, m::REPL.LineEdit.ModalInterface, s::REPL.LineEdit.MIState)
    @ REPL.LineEdit ~/.julia/juliaup/julia-1.11.5+0.aarch64.apple.darwin14/share/julia/stdlib/v1.11/REPL/src/LineEdit.jl:2755
 [12] run_interface
    @ ~/.julia/juliaup/julia-1.11.5+0.aarch64.apple.darwin14/share/julia/stdlib/v1.11/REPL/src/LineEdit.jl:2749 [inlined]
 [13] RunDebugger(frame::JuliaInterpreter.Frame, repl::Nothing, terminal::Nothing; initial_continue::Bool)
    @ Debugger ~/.julia/packages/Debugger/wueAn/src/repl.jl:167
 [14] RunDebugger
    @ ~/.julia/packages/Debugger/wueAn/src/repl.jl:12 [inlined]
 [15] RunDebugger(frame::JuliaInterpreter.Frame)
    @ Debugger ~/.julia/packages/Debugger/wueAn/src/repl.jl:12
 [16] macro expansion
    @ ~/.julia/packages/Debugger/wueAn/src/Debugger.jl:127 [inlined]
 [17] top-level scope
    @ REPL[3]:1

caused by: TypeError: in specializations, expected DataType, got Type{Union{}}
Stacktrace:
  [1] #specialize_method#317
    @ ./compiler/utilities.jl:224 [inlined]
  [2] specialize_method
    @ ./compiler/utilities.jl:212 [inlined]
  [3] Base.StackTraces.StackFrame(frame::JuliaInterpreter.Frame)
    @ JuliaInterpreter ~/.julia/packages/JuliaInterpreter/ZNccU/src/utils.jl:773
  [4] show_backtrace(io::IOContext{IOBuffer}, frame::JuliaInterpreter.Frame)
    @ JuliaInterpreter ~/.julia/packages/JuliaInterpreter/ZNccU/src/utils.jl:792
  [5] showerror(io::IOContext{IOBuffer}, ex::BoundsError, bt::JuliaInterpreter.Frame; backtrace::Bool)
    @ Base ./errorshow.jl:99
  [6] showerror
    @ ./errorshow.jl:95 [inlined]
  [7] display_error(io::IOContext{IOBuffer}, er::BoundsError, frame::JuliaInterpreter.Frame)
    @ JuliaInterpreter ~/.julia/packages/JuliaInterpreter/ZNccU/src/utils.jl:808
  [8] show_breakpoint(io::Base.TTY, bp::JuliaInterpreter.BreakpointRef, state::Debugger.DebuggerState)
    @ Debugger ~/.julia/packages/Debugger/wueAn/src/commands.jl:22
  [9] execute_command(state::Debugger.DebuggerState, v::Val{:c}, cmd::SubString{String})
    @ Debugger ~/.julia/packages/Debugger/wueAn/src/commands.jl:56
 [10] (::Debugger.var"#10#19"{REPL.LineEdit.Prompt, Debugger.DebuggerState})(s::REPL.LineEdit.MIState, buf::IOBuffer, ok::Bool)
    @ Debugger ~/.julia/packages/Debugger/wueAn/src/repl.jl:64
 [11] #invokelatest#2
    @ ./essentials.jl:1055 [inlined]
 [12] invokelatest
    @ ./essentials.jl:1052 [inlined]
 [13] run_interface(terminal::REPL.Terminals.TextTerminal, m::REPL.LineEdit.ModalInterface, s::REPL.LineEdit.MIState)
    @ REPL.LineEdit ~/.julia/juliaup/julia-1.11.5+0.aarch64.apple.darwin14/share/julia/stdlib/v1.11/REPL/src/LineEdit.jl:2755
 [14] run_interface
    @ ~/.julia/juliaup/julia-1.11.5+0.aarch64.apple.darwin14/share/julia/stdlib/v1.11/REPL/src/LineEdit.jl:2749 [inlined]
 [15] RunDebugger(frame::JuliaInterpreter.Frame, repl::Nothing, terminal::Nothing; initial_continue::Bool)
    @ Debugger ~/.julia/packages/Debugger/wueAn/src/repl.jl:167
 [16] RunDebugger
    @ ~/.julia/packages/Debugger/wueAn/src/repl.jl:12 [inlined]
 [17] RunDebugger(frame::JuliaInterpreter.Frame)
    @ Debugger ~/.julia/packages/Debugger/wueAn/src/repl.jl:12
 [18] macro expansion
    @ ~/.julia/packages/Debugger/wueAn/src/Debugger.jl:127 [inlined]
 [19] top-level scope
    @ REPL[3]:1

I tried to debug the debugger with @run @run ... but it just gave me a different error:

Breaking for error:
ERROR: ArgumentError: _deleteend! requires delta in 0:length(a)
Stacktrace:
 [1] _deleteend!(a::Vector{JuliaInterpreter.FrameData}, delta::Int64)
   @ Base array.jl:1204
 [2] empty!(a::Vector{JuliaInterpreter.FrameData})
   @ Base array.jl:2029
 [3] clear_caches()
   @ JuliaInterpreter ~/.julia/packages/JuliaInterpreter/ZNccU/src/construct.jl:59
 [4] enter_call_expr(expr::Expr; enter_generated::Bool)
   @ JuliaInterpreter ~/.julia/packages/JuliaInterpreter/ZNccU/src/construct.jl:630
 [5] enter_call_expr(expr::Expr)
   @ JuliaInterpreter ~/.julia/packages/JuliaInterpreter/ZNccU/src/construct.jl:629
 [6] var"##thunk#270"()
   @ Main ~/.julia/packages/Debugger/wueAn/src/Debugger.jl:91

In _deleteend!(a, delta) at array.jl:1201
 1201  function _deleteend!(a::Vector, delta::Integer)
 1202      delta = Int(delta)
 1203      len = length(a)
>1204      0 <= delta <= len || throw(ArgumentError("_deleteend! requires delta in 0:length(a)"))
 1205      newlen = len - delta
 1206      for i in newlen+1:len
 1207          @inbounds _unsetindex!(a, i)
 1208      end

About to run: throw(ArgumentError("_deleteend! requires delta in 0:length(a)"))
1|debug> bt
[1] _deleteend!(a, delta) at array.jl:1204
  | a::Vector{JuliaInterpreter.FrameData} = <JuliaInterpreter.FrameData[JuliaInterpreter.FrameData(Union{Nothing, Some{Any}}[Some(Core.toInt64), S...>
  | delta::Int64 = 29
  | len::Int64 = 28
  | ::Bool = false
[2] empty!(a) at array.jl:2029
  | a::Vector{JuliaInterpreter.FrameData} = <JuliaInterpreter.FrameData[JuliaInterpreter.FrameData(Union{Nothing, Some{Any}}[Some(Core.toInt64), S...>
[3] clear_caches() at /Users/akriegma/.julia/packages/JuliaInterpreter/ZNccU/src/construct.jl:59
[4] #enter_call_expr#46(enter_generated, , expr) at /Users/akriegma/.julia/packages/JuliaInterpreter/ZNccU/src/construct.jl:630
  | enter_generated::Bool = false
  | ::typeof(JuliaInterpreter.enter_call_expr) = JuliaInterpreter.enter_call_expr
  | expr::Expr = <:((VM(Float32[-0.06815089 0.027055124 0.046305846 -0.02320608 0.0076302057 -0.035288677 0.073490456 -...>
[5] enter_call_expr(expr) at /Users/akriegma/.julia/packages/JuliaInterpreter/ZNccU/src/construct.jl:629
  | expr::Expr = <:((VM(Float32[-0.06815089 0.027055124 0.046305846 -0.02320608 0.0076302057 -0.035288677 0.073490456 -...>
[6] ##thunk#270() at REPL[4]:91
  | theargs::Tuple{VM, Matrix{Float64}} = <(VM(Float32[-0.06815089 0.027055124 0.046305846 -0.02320608 0.0076302057 -0.035288677 0.073490456 -0....>

So with that being the state of things I'm not sure how to gather more information about this error.

Start by reproducing the reported nested @run scenario and inspect the stack traces in JuliaInterpreter/src/utils.jl and src/construct.jl. Then trace the debugger paths in Debugger/src/repl.jl and src/commands.jl. Done means showing the original error and clearing interpreter caches no longer produce secondary TypeErrors or _deleteend! failures.