@hst337 it is already deprecated when we detect it is a map at compilation time:
Interactive Elixir (1.15.0-dev) - press Ctrl+C to exit (type h() ENTER for help)
iex(1)> defmodule Foo do
...(1)> def bar(map) when is_map(map) do
...(1)> map.foo()
...(1)> end
...(1)> end
warning: incompatible types:
map() !~ atom()
in expression:
# iex:3
map.foo()
where "map" was given the type map() in:
# iex:2
is_map(map)
where "map" was given the type atom() (due to calling var.fun()) in:
# iex:3
map.foo()
HINT: "var.field" (without parentheses) implies "var" is a map() while "var.fun()" (with parentheses) implies "var" is an atom()
Conflict found at
iex:3: Foo.bar/1
We have been planning on adding a runtime deprecation for a while and there is an open issue tracking this. 
