Excise last use of brittle extract_vars function

lib/chorex.ex

@@ -325,15 +325,7 @@ defmodule Chorex do
           | # params_ might have "_" in it when parameter not for
             # this label; do not add _ to ctx.vars
             vars:
-              (
-                params_
-                |> FreeVarAnalysis.free_vars()
-                |> Enum.map(&elem(&1, 0))
-                |> Enum.filter(fn
-                  :_ -> false
-                  _ -> true
-                end)
-              ) ++ ctx.vars
+              FreeVarAnalysis.extract_new_pattern_var_names(params_) ++ ctx.vars
         })
 
       # no return value from a function *definition*
@@ -673,8 +665,7 @@ defmodule Chorex do
           | vars:
               if(match?(^zero, match_expr_),
                 do: ctx.vars,
-                # FIXME: use FreeVarAnalysis
-                else: extract_vars(match_expr_) ++ ctx.vars
+                else: FreeVarAnalysis.extract_new_pattern_var_names(match_expr_) ++ ctx.vars
               )
         })
 
@@ -968,19 +959,6 @@ defmodule Chorex do
 
   def metadata({_, m, _}) when is_list(m), do: m
 
-  @doc """
-  Walk an expression and pull out all the names of all the variables embedded in it.
-  """
-  def extract_vars(expr) do
-    Macro.postwalk(expr, [], &grab_var/2)
-    |> elem(1)
-  end
-
-  def grab_var({var_name, _meta, ctx} = e, acc) when is_atom(var_name) and is_atom(ctx),
-    do: {e, [var_name | acc]}
-
-  def grab_var(node, acc), do: {node, acc}
-
   @doc """
   Walks a local expression to pull out/convert function calls.
 

lib/free_var_analysis.ex

@@ -115,6 +115,11 @@ defmodule FreeVarAnalysis do
     {free, MapSet.to_list(bound_set)}
   end
 
+  def extract_new_pattern_var_names(expr, bound \\ MapSet.new()) do
+    {_, newly_bound} = expr |> extract_pattern_vars(bound)
+    newly_bound |> Enum.map(&var_name/1)
+  end
+
   defp strip_meta({a, _, b}), do: {a, [], b}
 
   defp bound?(var, binds) when is_var(var), do: MapSet.member?(binds, strip_meta(var))

test/chorex_test.exs

@@ -515,35 +515,4 @@ defmodule ChorexTest do
                Chorex.project_local_expr(stx, __ENV__, Alice, Chorex.empty_ctx(__ENV__))
     end
   end
-
-  describe "extract_vars" do
-	test "basic variables" do
-      vars =
-        quote do
-          foo
-        end
-        |> extract_vars()
-
-      assert [:foo] = vars
-
-      vars =
-        quote do
-          bar
-          baz
-        end
-        |> extract_vars()
-
-      assert [:baz, :bar] = vars
-	end
-
-    test "tuples" do
-      vars =
-        quote do
-          {thing1, thing2}
-        end
-        |> extract_vars()
-
-      assert [:thing2, :thing1] = vars
-    end
-  end
 end