The issue was because struct is also a map. Adding one match in lambda at the beginning did the trick:
Enum.reduce(to_merge, base, fn
{key, %{__struct__: _} = value}, base ->
Map.put(base, key, value)
{key, %{} = value}, base ->
sub = base[key] || %{}
sub = if is_map(sub), do: deep_merge_map(sub, value), else: sub
Map.put(base, key, sub)
{key, value}, base ->
Map.put(base, key, value)
end)
@wlminimal, it should be fixed by now, you may check the github master now, or wait for 0.9.2 (coming probably tonight).
You are relying on an implementation detail of structs, can’t you use proper syntax support instead:
iex(1)> defmodule S do
...(1)> defstruct a: 0
...(1)> end
iex(2)> %_{} = %S{}
%S{a: 0}
iex(3)> %_{} = %{}
** (MatchError) no match of right hand side value: %{}