show_method_table error

[vtjnash]

#45069 seems to assume that mt[1] value is meaningful (though it seems probably never true), and crashes if is isn't

julia> @time methods(Base.Broadcast.BroadcastStyle, Tuple{Type{<:Any}})
  0.004502 seconds (2.26 k allocations: 75.891 KiB)
# 45 methods for type constructor:Error showing value of type Base.MethodList:
ERROR: "BroadcastStyle" is not defined in module RecursiveArrayTools
Stacktrace:
  [1] error(s::String)
    @ Base ./error.jl:35
  [2] which(m::Module, s::Symbol)
    @ Base ./reflection.jl:1632
  [3] show_method_table(io::IOContext{Base.TTY}, ms::Base.MethodList, max::Int64, header::Bool)
    @ Base ./methodshow.jl:303
  [4] show_method_table
    @ ./methodshow.jl:289 [inlined]
  [5] show(io::IOContext{Base.TTY}, ::MIME{Symbol("text/plain")}, ms::Base.MethodList)
    @ Base ./methodshow.jl:349
  [6] (::REPL.var"#55#56"{REPL.REPLDisplay{REPL.LineEditREPL}, MIME{Symbol("text/plain")}, Base.RefValue{Any}})(io::Any)
    @ REPL ~/julia/usr/share/julia/stdlib/v1.10/REPL/src/REPL.jl:271
  [7] with_repl_linfo(f::Any, repl::REPL.LineEditREPL)
    @ REPL ~/julia/usr/share/julia/stdlib/v1.10/REPL/src/REPL.jl:552
  [8] display(d::REPL.REPLDisplay, mime::MIME{Symbol("text/plain")}, x::Any)
    @ REPL ~/julia/usr/share/julia/stdlib/v1.10/REPL/src/REPL.jl:259
  [9] display(d::REPL.REPLDisplay, x::Any)
    @ REPL ~/julia/usr/share/julia/stdlib/v1.10/REPL/src/REPL.jl:276
 [10] display(x::Any)
    @ Base.Multimedia ./multimedia.jl:340
 [11] #invokelatest#2
    @ ./essentials.jl:863 [inlined]
 [12] invokelatest
    @ ./essentials.jl:860 [inlined]
 [13] print_response(errio::IO, response::Any, show_value::Bool, have_color::Bool, specialdisplay::Union{Nothing, AbstractDisplay})
    @ REPL ~/julia/usr/share/julia/stdlib/v1.10/REPL/src/REPL.jl:300
 [14] (::REPL.var"#57#58"{REPL.LineEditREPL, Pair{Any, Bool}, Bool, Bool})(io::Any)
    @ REPL ~/julia/usr/share/julia/stdlib/v1.10/REPL/src/REPL.jl:282
 [15] with_repl_linfo(f::Any, repl::REPL.LineEditREPL)
    @ REPL ~/julia/usr/share/julia/stdlib/v1.10/REPL/src/REPL.jl:552
 [16] print_response(repl::REPL.AbstractREPL, response::Any, show_value::Bool, have_color::Bool)
    @ REPL ~/julia/usr/share/julia/stdlib/v1.10/REPL/src/REPL.jl:280
 [17] (::REPL.var"#do_respond#80"{Bool, Bool, REPL.var"#93#103"{REPL.LineEditREPL, REPL.REPLHistoryProvider}, REPL.LineEditREPL, REPL.LineEdit.Prompt})(s::REPL.LineEdit.MIState, buf::Any, ok::Bool)
    @ REPL ~/julia/usr/share/julia/stdlib/v1.10/REPL/src/REPL.jl:894
 [18] #invokelatest#2
    @ ./essentials.jl:863 [inlined]
 [19] invokelatest
    @ ./essentials.jl:860 [inlined]
 [20] run_interface(terminal::REPL.Terminals.TextTerminal, m::REPL.LineEdit.ModalInterface, s::REPL.LineEdit.MIState)
    @ REPL.LineEdit ~/julia/usr/share/julia/stdlib/v1.10/REPL/src/LineEdit.jl:2648
 [21] run_frontend(repl::REPL.LineEditREPL, backend::REPL.REPLBackendRef)
    @ REPL ~/julia/usr/share/julia/stdlib/v1.10/REPL/src/REPL.jl:1295
 [22] (::REPL.var"#62#68"{REPL.LineEditREPL, REPL.REPLBackendRef})()
    @ REPL ./task.jl:514

[fredrikekre]

Looks like a duplicate if #49382

[ararslan]

Duplicate of #49382

Hi, I'm learning from this issue. I could not find the reference to mt[1], what is it? Is it clear what the underlying error is?

[ararslan]

Hi @persinammon! I believe by mt[1], @vtjnash is actually referring to ms.ms[1] as in this line of the linked PR. Here, ms is a MethodList and its .ms field is an array of Methods, and the code is assuming that the location of the first method in that array is meaningful.

Taking the OpaqueClosure example from #52043:

julia> ms = methods(Core.OpaqueClosure);  # suppress output with ; to avoid the error

julia> ms.ms[1]
Core.OpaqueClosure(ir::Core.Compiler.IRCode, env...; nargs, isva, rt)
     @ Base.Experimental opaque_closure.jl:58

julia> (ms.ms[1].module, ms.ms[1].name)
(Base.Experimental, :OpaqueClosure)

julia> isdefined(ms.ms[1].module, ms.ms[1].name)
false

Since OpaqueClosure isn't defined in Base.Experimental, the call to which as in the linked PR errors.