Raise an exception if var!(x) does not expand to a proper var

Author: José Valim

lib/elixir/src/elixir_scope.erl

@@ -1,7 +1,7 @@
 %% Convenience functions used to manipulate scope
 %% and its variables.
 -module(elixir_scope).
--export([translate_var/4,
+-export([translate_var/5,
   build_erl_var/2, build_ex_var/2,
   build_erl_var/3, build_ex_var/3,
   build_erl_var/4, build_ex_var/4,
@@ -13,7 +13,7 @@
 -include("elixir.hrl").
 -compile({parse_transform, elixir_transform}).
 
-translate_var(Meta, Name, Kind, S) ->
+translate_var(Meta, Name, Kind, S, Callback) ->
   Line = ?line(Meta),
   Vars = S#elixir_scope.vars,
 
@@ -48,7 +48,7 @@ translate_var(Meta, Name, Kind, S) ->
         _ ->
           case orddict:find({ Name, Kind }, Vars) of
             { ok, VarName } -> { { var, Line, VarName }, S };
-            error -> elixir_translator:translate_each({ Name, Meta, [] }, S)
+            error -> Callback()
           end
       end
   end.

lib/elixir/src/elixir_translator.erl

@@ -329,12 +329,13 @@ translate_each({ 'var!', Meta, [Arg] }, S) ->
   translate_each({ 'var!', Meta, [Arg, nil] }, S);
 
 translate_each({ 'var!', Meta, [{Name, _, Atom}, Kind] }, S) when is_atom(Name), is_atom(Atom) ->
-  Expanded = expand_var_context(Meta, Kind, "invalid second argument for var!", S),
-  elixir_scope:translate_var(Meta, Name, Expanded, S);
+  translate_each({ 'var!', Meta, [Name, Kind] }, S);
 
 translate_each({ 'var!', Meta, [Name, Kind] }, S) when is_atom(Name) ->
   Expanded = expand_var_context(Meta, Kind, "invalid second argument for var!", S),
-  elixir_scope:translate_var(Meta, Name, Expanded, S);
+  elixir_scope:translate_var(Meta, Name, Expanded, S, fun() ->
+    syntax_error(Meta, S#elixir_scope.file, "expected var!(~ts) to expand to an existing variable or be a part of a match", [Name])
+  end);
 
 translate_each({ 'var!', Meta, [_, _] }, S) ->
   syntax_error(Meta, S#elixir_scope.file, "invalid first argument for var!, expected a var or an atom");
@@ -400,7 +401,9 @@ translate_each({ '^', Meta, [ { Name, _, Kind } ] }, S) when is_atom(Kind) ->
     "cannot access variable ^~s outside of assignment", [Name]);
 
 translate_each({ Name, Meta, Kind }, S) when is_atom(Name), is_atom(Kind) ->
-  elixir_scope:translate_var(Meta, Name, Kind, S);
+  elixir_scope:translate_var(Meta, Name, Kind, S, fun() ->
+    translate_each({ Name, Meta, [] }, S)
+  end);
 
 %% Local calls
 

lib/elixir/test/elixir/kernel/errors_test.exs

@@ -184,6 +184,11 @@ defmodule Kernel.ErrorsTest do
     assert "nofile:1: unit in bitstring expects an integer as argument" == format_rescue '<<1 :: unit(x)>>'
   end
 
+  test :invalid_var! do
+    assert "nofile:1: expected var!(y) to expand to an existing variable or be a part of a match",
+      format_rescue 'var!(x)'
+  end
+
   test :invalid_alias do
     assert "nofile:1: invalid args for alias, cannot create nested alias Sample.Lists" ==
       format_rescue 'alias :lists, as: Sample.Lists'