toivoh

macro expect(pred)
    :( ($esc(pred)) ? nothing : error($"error: expected $pred == true") )
end

is_expr(ex, head::Symbol) = (isa(ex, Expr) && (ex.head == head))

function split_fdef(fdef::Expr)
    @expect (fdef.head == :function) || (fdef.head == :(=))
    @expect length(fdef.args) == 2
    signature, body = tuple(fdef.args...)

toivoh

code = quote
    function show_body_lines(io::IO, ex)
        args = is_expr(ex, :block) ? ex.args : {ex}
        for arg in args
            if !is_linenumber(arg); print(io, '\n'); end
            show(io, arg)
        end
    end
end

toivoh

require("recshow.jl")

type T
    x
    y
end

type Unshowable; end
show(io::IO, x::Unshowable) = error("Tried to show Unshowable()")

toivoh

# ---- ObjNode: capture of an object's output to show() -----------------------

type ObjNode
    # actual capture
    obj
    reused::Bool
    items::Vector   # ObjNode:s and strings/chars

    # scratch space for recshow etc
    strlen::Integer

toivoh

# union of immutable types not to freeze/unfreeze
typealias NoFreeze Union(Number, String)

type Frozen{T,COUNT}
    item::T
    watchers::Set{WeakRef}
end

typealias FrozenArray{T,N,COUNT} Frozen{Array{T,N},COUNT}