1.18+: change struct updates to map updates. Closes #199

Author: novaugust

CHANGELOG.md

@@ -11,6 +11,19 @@ they can and will change without that change being reflected in Styler's semanti
 
 Replace `:timer.units(x)` with the new `to_timeout(unit: x)` for `hours|minutes|seconds`
 
+#### Ex1.18+
+
+Delete deprecated struct update syntax in favor of map update syntax.
+
+```elixir
+# This
+%Struct{x | y}
+# Styles to this
+%{x | y}
+```
+
+**WARNING** Double check your diffs to make sure your variable is pattern matching against the same struct if you want to harness 1.18's type checking features. (#199, h/t @SteffenDE)
+
 #### Alias Lifting
 
 This release taught Styler to try just that little bit harder when doing alias lifting.

lib/style/deprecations.ex

@@ -65,6 +65,11 @@ defmodule Styler.Style.Deprecations do
     end
   end
 
+  if Version.match?(System.version(), ">= 1.18.0-dev") do
+    # Struct update syntax was deprecated `%Foo{x | y} => %{x | y}`
+    defp style({:%, _, [_struct, {:%{}, _, [{:|, _, _}]} = update]}), do: update
+  end
+
   # For ranges where `start > stop`, you need to explicitly include the step
   # Enum.slice(enumerable, 1..-2) => Enum.slice(enumerable, 1..-2//1)
   # String.slice("elixir", 2..-1) => String.slice("elixir", 2..-1//1)

test/style/deprecations_test.exs

@@ -145,4 +145,12 @@ defmodule Styler.Style.DeprecationsTest do
       assert_style "a |> x() |> :timer.seconds()"
     end
   end
+
+  describe "1.18+" do
+    @describetag skip: Version.match?(System.version(), "< 1.18.0-dev")
+
+    test "struct update" do
+      assert_style "%Foo{widget | bar: :baz}", "%{widget | bar: :baz}"
+    end
+  end
 end

test/style/pipes_test.exs

@@ -408,7 +408,7 @@ defmodule Styler.Style.PipesTest do
         """,
         """
         def halt(exec, halt_message) do
-          put_halt_message(%__MODULE__{exec | halted: true}, halt_message)
+          put_halt_message(%{exec | halted: true}, halt_message)
         end
         """
       )