Fix: Macro.expand/2 should not expand __ENV__ on :match context (#13807)

Author: sabiwara

lib/elixir/lib/macro.ex

@@ -1832,13 +1832,13 @@ defmodule Macro do
   defp do_expand_once({:__DIR__, _, atom}, env) when is_atom(atom),
     do: {:filename.dirname(env.file), true}
 
-  defp do_expand_once({:__ENV__, _, atom}, env) when is_atom(atom) do
+  defp do_expand_once({:__ENV__, _, atom}, env) when is_atom(atom) and env.context != :match do
     env = update_in(env.versioned_vars, &maybe_escape_map/1)
     {maybe_escape_map(env), true}
   end
 
   defp do_expand_once({{:., _, [{:__ENV__, _, atom}, field]}, _, []} = original, env)
-       when is_atom(atom) and is_atom(field) do
+       when is_atom(atom) and is_atom(field) and env.context != :match do
     if Map.has_key?(env, field) do
       {maybe_escape_map(Map.get(env, field)), true}
     else

lib/elixir/test/elixir/macro_test.exs

@@ -196,6 +196,16 @@ defmodule MacroTest do
       assert Code.eval_quoted(expanded) == {env.versioned_vars, []}
     end
 
+    test "env in :match context does not expand" do
+      env = %{__ENV__ | line: 0, lexical_tracker: self(), context: :match}
+
+      expanded = Macro.expand_once(quote(do: __ENV__), env)
+      assert expanded == quote(do: __ENV__)
+
+      expanded = Macro.expand_once(quote(do: __ENV__.file), env)
+      assert expanded == quote(do: __ENV__.file)
+    end
+
     defmacro local_macro(), do: raise("ignored")
 
     test "vars" do

lib/ex_unit/test/ex_unit/assertions_test.exs

@@ -256,6 +256,28 @@ defmodule ExUnit.AssertionsTest do
     end
   end
 
+  test "assert match with __ENV__ in the pattern" do
+    message =
+      ExUnit.CaptureIO.capture_io(:stderr, fn ->
+        assert_raise CompileError, fn ->
+          Code.eval_string("""
+          defmodule EnvMatch do
+            import ExUnit.Assertions
+
+            def run do
+              assert __ENV__ = %{}
+            end
+          end
+          """)
+        end
+      end)
+
+    assert message =~ "invalid pattern in match, __ENV__ is not allowed in matches"
+  after
+    :code.purge(EnvMatch)
+    :code.delete(EnvMatch)
+  end
+
   test "assert match?" do
     true = assert match?({2, 1}, Value.tuple())