Deprecate var!(:atom), add Macro.var/1

Author: José Valim

lib/elixir/lib/kernel.ex

@@ -2733,6 +2733,8 @@ defmodule Kernel do
   defmacro var!(var, context \\ nil)
 
   defmacro var!(var, context) when is_atom(var) do
+    IO.write :stderr, "passing an atom to var! is deprecated\n" <>
+                      Exception.format_stacktrace(Macro.Env.stacktrace(__CALLER__))
     do_var!(var, [], context, __CALLER__)
   end
 

lib/elixir/lib/macro.ex

@@ -109,6 +109,15 @@ defmodule Macro do
     other
   end
 
+  @doc """
+  Genrates a AST node representing the variable given
+  by the atoms `var` and `context`.
+  """
+  @spec var(var, context) :: {var, [], context} when var: atom, context: atom
+  def var(var, context \\ nil) when is_atom(var) and is_atom(context) do
+    {var, [], context}
+  end
+
   @doc """
   Performs a depth-first, pre-order traversal of quoted expressions.
   """

lib/elixir/test/elixir/kernel/quote_test.exs

@@ -229,7 +229,7 @@ defmodule Kernel.QuoteTest.VarHygiene do
   end
 
   defmacro cross_module_interference do
-    quote do: var!(:a, Kernel.QuoteTest.VarHygieneTest) = 1
+    quote do: var!(a, Kernel.QuoteTest.VarHygieneTest) = 1
   end
 end
 

lib/elixir/test/elixir/macro_test.exs

@@ -232,6 +232,11 @@ defmodule MacroTest do
     end)
   end
 
+  test :var do
+    assert Macro.var(:foo) == {:foo, [], nil}
+    assert Macro.var(:foo, Other) == {:foo, [], Other}
+  end
+
   ## to_string
 
   test :var_to_string do