TypeTreesIO

This is a prototype of an IO subtype that prints Julia's parametric types as a tree. This is intended to support omitting or folding types when printing stacktraces, c.f. JuliaLang/julia#48444 (comment).

Demo:

using TypeTreesIO, AbstractTrees

AbstractTrees.children(node::TypeTreeNode) = (v = node.children; v === nothing ? () : v)
AbstractTrees.nodevalue(node::TypeTreeNode) = node.name

julia> obj = view([1, 2, 3], 1:2);    # a parametric type

julia> println(typeof(obj))           # what is that type?
SubArray{Int64, 1, Vector{Int64}, Tuple{UnitRange{Int64}}, true}

julia> ttio = TypeTreeIO();           # create the IO object that assembles a tree-of-strings structure

julia> print(ttio, typeof(obj));      # build the tree

julia> print_tree(ttio.tree)          # show the tree structure (from AbstractTrees)
"SubArray"
├─ "Int64"
├─ "1"
├─ "Vector"
│  └─ "Int64"
├─ "Tuple"
│  └─ "UnitRange"
│     └─ "Int64"
└─ "true"

julia> println(IOContext(stdout, :type_maxwidth=>55), ttio.tree)
SubArray{Int64, 1, Vector{…}, Tuple{…}, true}

julia> println(IOContext(stdout, :type_maxwidth=>60), ttio.tree)
SubArray{Int64, 1, Vector{Int64}, Tuple{UnitRange{…}}, true}