I just had the idea that I would create a struct with some fields in uppercase, and I ran in to a lot of seemingly weird behaviour.

Given this code:

defmodule Lower do
  defstruct lower: "lower"
end

defmodule Upper do
  defstruct UPPER: "UPPER"
end

When I try these out in IEx, I can instantiate them just fine, and I can type lower. and hit the tab-key, and it prints the fields, but I can’t seem to tab-complete the UPPER field on an %Upper{} struct, and if I manually type it out, I get an error message:

iex(38)> lower = %Lower{}
%Lower{lower: "lower"}
iex(39)> lower.
__struct__    lower         
iex(39)> lower.lower
"lower"
iex(40)> upper = %Upper{}
%Upper{UPPER: "UPPER"}
iex(41)> upper.
UPPER         __struct__    
iex(41)> upper.UPPER
** (CompileError) iex:41: invalid alias: "upper.UPPER". If you wanted to define an alias, an alias must expand to an atom at compile time but it did not, you may use Module.concat/2 to build it at runtime. If instead you wanted to invoke a function or access a field, wrap the function or field name in double quotes

Does anyone know if this is intended, and if so, where I can read up on why this happens?