Update CHANGELOG

Author: josevalim

CHANGELOG.md

@@ -30,16 +30,105 @@ end
 
 Even though the `+` operator works with both integers and floats, Elixir infers that `a` and `b` must be both integers, as the result of `+` is given to a function that expects an integer. The inferred type information is then used during type checking to find possible typing errors.
 
+### Complete typing of maps keys
+
+Maps were one of the first data-structures we implemented within the Elixir type system however, up to this point, they only supported atom keys. If they had additional keys, those keys were simply marked as `dynamic()`.
+
+As of Elixir v1.20, we can track all possible domains as map keys. For example, the map:
+
+```elixir
+%{123 => "hello", 456.0 => :ok}
+```
+
+will have the type:
+
+```elixir
+%{integer() => binary(), float() => :ok}
+```
+
+It is also possible to mix domain keys, as above, with atom keys, yielding the following:
+
+```elixir
+%{integer() => integer(), root: integer()}
+```
+
+This system is an implementation of [Polymorphic Records for Dynamic Languages, by Giuseppe Castagna and Loïc Peyrot (2024)](https://arxiv.org/abs/2404.00338).
+
+### Typing of map operations
+
+We have typed the majority of the functions in the `Map` module, allowing the type system to track how keys are added, updated, and removed across all possible key types.
+
+For example, imagine we are calling the following `Map` functions with a variable `map`, which we don't know the exact shape of, and an atom key:
+
+```elixir
+Map.put(map, :key, 123)
+#=> returns type %{..., key: integer()}
+
+Map.delete(map, :key)
+#=> returns type %{..., key: not_set()}
+```
+
+As you can see, when track when keys are set and also when they are removed.
+
+Some operations, like `Map.replace/3`, only replace the key if it exists, and that is also propagated by the type system:
+
+```elixir
+Map.replace(map, :key, 123)
+#=> returns type %{..., key: if_set(integer())}
+```
+
+In other words, if the key exists, it would have been replaced by an integer value. Furthermore, whenever calling a function in the `Map` module and the given key is statically proven to never exist in the map, an error is emitted.
+
+By combining full type inference with bang operations like `Map.fetch!/2`, `Map.pop!/2`, `Map.replace!/2`, and `Map.update!/3`, Elixir is able to propagate information about the desired keys. Take this module:
+
+```elixir
+defmodule User do
+  def name(map), do: Map.fetch!(map, :name)
+end
+
+defmodule CallsUser do
+  def calls_name do
+    User.name(%{})
+  end
+end
+```
+
+The code above has a type violation, which is now caught by the type system:
+
+```
+    warning: incompatible types given to User.name/1:
+
+        User.name(%{})
+
+    given types:
+
+        %{name: not_set()}
+
+    but expected one of:
+
+        dynamic(%{..., name: term()})
+
+    typing violation found at:
+    │
+ 16 │     User.name(%{})
+    │         ~
+    │
+    └─ lib/calls_user.ex:7:5: CallsUser.calls_name/0
+```
+
+Once again, our goal is to propagate type information and help developers find bugs in their code, without a need to introduce type signatures (yet).
+
 ### Acknowledgements
 
-The type system was made possible thanks to a partnership between [CNRS](https://www.cnrs.fr/) and [Remote](https://remote.com/). The development work is currently sponsored by [Fresha](https://www.fresha.com/) and [Dashbit](https://dashbit.co/).
+The type system was made possible thanks to a partnership between [CNRS](https://www.cnrs.fr/) and [Remote](https://remote.com/). The development work is currently sponsored by [Fresha](https://www.fresha.com/) and [Tidewave](https://tidewave.ai/).
 
 ## v1.20.0-dev
 
 ### 1. Enhancements
 
 #### Elixir
 
+  * [Calendar] Optimize `date_from_iso_days` by using the Neri-Schneider algorithm
   * [Enum] Add `Enum.min_max` sorter
   * [Integer] Add `Integer.ceil_div/2`
   * [Kernel] Print intermediate results of `dbg` for pipes
@@ -52,6 +141,7 @@ The type system was made possible thanks to a partnership between [CNRS](https:/
 
 #### Mix
 
+  * [mix deps] Support filtering `mix deps` output
   * [mix test] Add `mix test --dry-run`
 
 ### 2. Bug fixes