REPL autocompletion

[ranocha]

We are experimenting with the current master branch of Clang.jl in trixi-framework/P4est.jl#38. I noticed that there is no REPL tab completion for properties and structs defined automatically by Clang.jl (via field_access_method_list in the TOML file). For example, we get the following Julia code in the PR listed above.

struct p4est
    mpicomm::sc_MPI_Comm
    mpisize::Cint
    mpirank::Cint
    mpicomm_owned::Cint
    data_size::Csize_t
    user_pointer::Ptr{Cvoid}
    revision::Clong
    first_local_tree::p4est_topidx_t
    last_local_tree::p4est_topidx_t
    local_num_quadrants::p4est_locidx_t
    global_num_quadrants::p4est_gloidx_t
    global_first_quadrant::Ptr{p4est_gloidx_t}
    global_first_position::Ptr{p4est_quadrant_t}
    connectivity::Ptr{p4est_connectivity_t}
    trees::Ptr{sc_array_t}
    user_data_pool::Ptr{sc_mempool_t}
    quadrant_pool::Ptr{sc_mempool_t}
    inspect::Ptr{p4est_inspect_t}
end

function Base.getproperty(x::Ptr{p4est}, f::Symbol)
    f === :mpicomm && return Ptr{sc_MPI_Comm}(x + 0)
    f === :mpisize && return Ptr{Cint}(x + 4)
    f === :mpirank && return Ptr{Cint}(x + 8)
    f === :mpicomm_owned && return Ptr{Cint}(x + 12)
    f === :data_size && return Ptr{Csize_t}(x + 16)
    f === :user_pointer && return Ptr{Ptr{Cvoid}}(x + 24)
    f === :revision && return Ptr{Clong}(x + 32)
    f === :first_local_tree && return Ptr{p4est_topidx_t}(x + 40)
    f === :last_local_tree && return Ptr{p4est_topidx_t}(x + 44)
    f === :local_num_quadrants && return Ptr{p4est_locidx_t}(x + 48)
    f === :global_num_quadrants && return Ptr{p4est_gloidx_t}(x + 56)
    f === :global_first_quadrant && return Ptr{Ptr{p4est_gloidx_t}}(x + 64)
    f === :global_first_position && return Ptr{Ptr{p4est_quadrant_t}}(x + 72)
    f === :connectivity && return Ptr{Ptr{p4est_connectivity_t}}(x + 80)
    f === :trees && return Ptr{Ptr{sc_array_t}}(x + 88)
    f === :user_data_pool && return Ptr{Ptr{sc_mempool_t}}(x + 96)
    f === :quadrant_pool && return Ptr{Ptr{sc_mempool_t}}(x + 104)
    f === :inspect && return Ptr{Ptr{p4est_inspect_t}}(x + 112)
    return getfield(x, f)
end

However, tab completion in the REPL does not work for Ptr{p4est}, i.e. there is no useful suggestion when typing x. and tab. It would be great to get this kind of REPL tab completion.

[Gnimuc]

We need to emit Base.propertynames exprs for those Ptr types.