Ensure comprehensions with guards and filters keep proper ordering, closes #5509

Signed-off-by: José Valim <jose.valim@plataformatec.com.br>

Author: José Valim

lib/elixir/src/elixir_for.erl

@@ -114,7 +114,9 @@ translate_gen(_Meta, Left, Right, T, S) ->
   SF = SL#elixir_scope{extra=S#elixir_scope.extra, extra_guards=nil},
 
   {TT, {TFilters, TS}} = translate_filters(T, SF),
-  Guards = ExtraGuards ++ translate_guards(TLeftGuards) ++ TFilters,
+
+  %% The list of guards is kept in reverse order
+  Guards = TFilters ++ translate_guards(TLeftGuards) ++ ExtraGuards,
   {TLeft, TRight, Guards, TT, TS}.
 
 translate_guards([]) ->

lib/elixir/test/elixir/kernel/comprehension_test.exs

@@ -51,6 +51,12 @@ defmodule Kernel.ComprehensionTest do
     assert for(x when x == 3 when x == 7 <- 1..10, do: x) == [3, 7]
   end
 
+  test "for comprehensions with guards and filters" do
+    assert for({var, _} when is_atom(var) <- [{:foo, 1}, {2, :bar}],
+               var = Atom.to_string(var),
+               do: var) == ["foo"]
+  end
+
   test "for comprehensions with map key matching" do
     maps = [%{x: 1}, %{y: 2}, %{x: 3}]
     assert for(%{x: v} <- maps, do: v * 2) == [2, 6]