Ensure variables in function clauses are not reused, closes #4815

Author: José Valim

lib/elixir/src/elixir_fn.erl

@@ -8,7 +8,7 @@ translate(Meta, Clauses, S) ->
     {Args, Guards} = elixir_clauses:extract_splat_guards(ArgsWithGuards),
     {TClause, TS } = elixir_clauses:clause(CMeta, fun translate_fn_match/2,
                                             Args, Expr, Guards, Acc),
-    {TClause, elixir_scope:mergef(S, TS)}
+    {TClause, elixir_scope:mergec(S, TS)}
   end,
 
   {TClauses, NS} = lists:mapfoldl(Transformer, S, Clauses),

lib/elixir/src/elixir_scope.erl

@@ -2,8 +2,7 @@
 -module(elixir_scope).
 -export([translate_var/4, build_var/2, context_info/1,
   load_binding/2, dump_binding/2,
-  mergev/2, mergec/2, mergef/2,
-  merge_vars/2, merge_opt_vars/2,
+  mergev/2, mergec/2, merge_vars/2, merge_opt_vars/2,
   warn_unsafe_var/4, warn_underscored_var_access/3, format_error/1
 ]).
 -include("elixir.hrl").
@@ -128,14 +127,6 @@ mergec(S1, S2) ->
     caller=S2#elixir_scope.caller
  }.
 
-%% Similar to mergec but does not merge the user vars counter.
-
-mergef(S1, S2) ->
-  S1#elixir_scope{
-    super=S2#elixir_scope.super,
-    caller=S2#elixir_scope.caller
- }.
-
 %% Mergers.
 
 merge_vars(V, V) -> V;

lib/elixir/test/elixir/kernel/fn_test.exs

@@ -18,6 +18,18 @@ defmodule Kernel.FnTest do
     refute (fn ^x -> true; _ -> false end).(1.0)
   end
 
+  test "case function hoisting does not affect anonymous fns" do
+    assert :undefined =
+             (if is_a?(:atom, 0) do
+                user = :defined
+              else
+                (fn() ->
+                  user = :undefined
+                  user
+                end).()
+              end)
+  end
+
   test "capture with access" do
     assert (&(&1[:hello])).([hello: :world]) == :world
   end

lib/elixir/test/elixir/kernel/macros_test.exs

@@ -48,7 +48,7 @@ defmodule Kernel.MacrosTest do
     assert_raise UndefinedFunctionError, fn -> x.value end
   end
 
-  test "bang do block" do
+  test "macros with bang and do block have proper precedence" do
     import Kernel.MacrosTest.Nested
     assert (do_identity! do 1 end) == 1
     assert (Kernel.MacrosTest.Nested.do_identity! do 1 end) == 1

lib/elixir/test/erlang/string_test.erl

@@ -15,7 +15,6 @@ extract_interpolations(String) ->
       Z
    end.
 
-
 % Interpolations
 
 extract_interpolations_without_interpolation_test() ->