Strange error for unsupported Julia version

General Usage
1

I am trying to set a minimum Julia version for a package I am developing.

I may be misunderstanding something, but I thought from the docs (10. Project.toml and Manifest.toml · Pkg.jl) that the way to do this is to put

[compat]
julia = "1.7.0"

into my Project.toml to declare that only julia-1.7.0 or newer (but less than julia-2.0.0) is supported.

However, after doing this, if I launch julia-1.6.5 and try to instantiate the package, I get a cryptic error message (included below), where I had expected something like ‘not compatible with julia<=1.7.0’. The actual error message is identical to the one I get if I remove the [compat] section from my Project.toml, so it seems my expectation that the entry there would do something is incorrect?

$ ~/pkg/julia-1.6.5/bin/julia --project
               _
   _       _ _(_)_     |  Documentation: https://docs.julialang.org
  (_)     | (_) (_)    |
   _ _   _| |_  __ _   |  Type "?" for help, "]?" for Pkg help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 1.6.5 (2021-12-19)
 _/ |\__'_|_|_|\__'_|  |  Official https://julialang.org/ release
|__/                   |

(moment_kinetics) pkg> instantiate
ERROR: AssertionError: sourcepath !== nothing
Stacktrace:
  [1] is_package_downloaded(ctx::Pkg.Types.Context, pkg::Pkg.Types.PackageSpec)
    @ Pkg.Operations /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.6/Pkg/src/Operations.jl:1789
  [2] #13
    @ /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.6/Pkg/src/Operations.jl:131 [inlined]
  [3] _all
    @ ./reduce.jl:923 [inlined]
  [4] #all#698
    @ ./reducedim.jl:886 [inlined]
  [5] all
    @ ./reducedim.jl:886 [inlined]
  [6] is_instantiated(ctx::Pkg.Types.Context)
    @ Pkg.Operations /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.6/Pkg/src/Operations.jl:131
  [7] instantiate(ctx::Pkg.Types.Context; manifest::Nothing, update_registry::Bool, verbose::Bool, platform::Base.BinaryPlatforms.Platform, allow_build::Bool, allow_autoprecomp::Bool, kwargs::Base.Iterators.Pairs{Union{}, Union{}, Tuple{}, NamedTuple{(), Tuple{}}})
    @ Pkg.API /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.6/Pkg/src/API.jl:1358
  [8] instantiate
    @ /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.6/Pkg/src/API.jl:1325 [inlined]
  [9] #instantiate#252
    @ /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.6/Pkg/src/API.jl:1321 [inlined]
 [10] instantiate()
    @ Pkg.API /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.6/Pkg/src/API.jl:1321
 [11] do_cmd!(command::Pkg.REPLMode.Command, repl::REPL.LineEditREPL)
    @ Pkg.REPLMode /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.6/Pkg/src/REPLMode/REPLMode.jl:405
 [12] do_cmd(repl::REPL.LineEditREPL, input::String; do_rethrow::Bool)
    @ Pkg.REPLMode /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.6/Pkg/src/REPLMode/REPLMode.jl:386
 [13] do_cmd
    @ /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.6/Pkg/src/REPLMode/REPLMode.jl:377 [inlined]
 [14] (::Pkg.REPLMode.var"#24#27"{REPL.LineEditREPL, REPL.LineEdit.Prompt})(s::REPL.LineEdit.MIState, buf::IOBuffer, ok::Bool)
    @ Pkg.REPLMode /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.6/Pkg/src/REPLMode/REPLMode.jl:550
 [15] #invokelatest#2
    @ ./essentials.jl:708 [inlined]
 [16] invokelatest
    @ ./essentials.jl:706 [inlined]
 [17] run_interface(terminal::REPL.Terminals.TextTerminal, m::REPL.LineEdit.ModalInterface, s::REPL.LineEdit.MIState)
    @ REPL.LineEdit /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.6/REPL/src/LineEdit.jl:2441
 [18] run_frontend(repl::REPL.LineEditREPL, backend::REPL.REPLBackendRef)
    @ REPL /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.6/REPL/src/REPL.jl:1126
 [19] (::REPL.var"#44#49"{REPL.LineEditREPL, REPL.REPLBackendRef})()
    @ REPL ./task.jl:411
2

I am not sure this has anything to do with the julia compat, but rather that a manifest on a new Julia version used on an older one can get some strange (non ideal) errors.