if not x, do: y => unless x, do: y

lib/style/blocks.ex

@@ -177,6 +177,10 @@ defmodule Styler.Style.Blocks do
       [{negator, _, [expr]}, [{do_, do_body}, {else_, else_body}]] when is_negator(negator) ->
         zipper |> Zipper.replace({:if, m, [expr, [{do_, else_body}, {else_, do_body}]]}) |> run(ctx)
 
+      # if not x, do: y => unless x, do: y
+      [{negator, _, [expr]}, [do_block]] when is_negator(negator) ->
+        zipper |> Zipper.replace({:unless, m, [expr, [do_block]]}) |> run(ctx)
+
       # drop `else: nil`
       [head, [do_block, {_, {:__block__, _, [nil]}}]] ->
         {:cont, Zipper.replace(zipper, {:if, m, [head, [do_block]]}), ctx}

test/style/blocks_test.exs

@@ -767,6 +767,11 @@ defmodule Styler.Style.BlocksTest do
       """)
     end
 
+    test "if not => unless" do
+      assert_style("if not x, do: y", "unless x, do: y")
+      assert_style("if !x, do: y", "unless x, do: y")
+    end
+
     test "Credo.Check.Refactor.UnlessWithElse" do
       for negator <- ["!", "not "] do
         assert_style(
@@ -826,15 +831,8 @@ defmodule Styler.Style.BlocksTest do
 
     test "Credo.Check.Refactor.NegatedConditionsWithElse" do
       for negator <- ["!", "not "] do
-        assert_style("if #{negator}foo, do: :bar")
         assert_style("if #{negator}foo, do: :bar, else: :baz", "if foo, do: :baz, else: :bar")
 
-        assert_style("""
-        if #{negator}foo do
-          bar
-        end
-        """)
-
         assert_style(
           """
           if #{negator}foo do