Why Julia returns error on myit .+ 1 in the following code?

General Usage
7

Here are my sources of information, so far:

  1. The manual (specifically the chapters about arrays, interfaces and broadcasting)
  2. The talk by Matt Bauman on the JuliaCon 2018 in London (An introduction to high performance custom arrays | Matt Bauman - YouTube(
  3. Matt Bauman’s post in the discourse: How to customize the new broadcasting infrastructure in v0.7 - #4 by mbauman
  4. JuliaLang.org blog entry about the broadcast function in 0.7 (Extensible broadcast fusion)

I almost never read the source code. I still hope to get a higher level explanation from the devs. :-)…