Prevent infinite loop in compiler for some invalid type specs (#14155)

lib/elixir/lib/kernel/typespec.ex

@@ -938,17 +938,20 @@ defmodule Kernel.Typespec do
 
   ## Helpers
 
-  # This is a backport of Macro.expand/2 because we want to expand
+  # This is a modified backport of Macro.expand/2 because we want to expand
   # aliases but we don't them to become compile-time references.
   defp expand_remote({:__aliases__, meta, list} = alias, env) do
     case :elixir_aliases.expand_or_concat(meta, list, env, true) do
       receiver when is_atom(receiver) ->
         receiver
 
       [head | tail] ->
-        case Macro.expand_once(head, env) do
-          head when is_atom(head) -> :elixir_aliases.concat([head | tail])
-          _ -> alias
+        case Macro.expand(head, env) do
+          head when is_atom(head) ->
+            :elixir_aliases.concat([head | tail])
+
+          _ ->
+            compile_error(env, "unexpected expression in typespec: #{Macro.to_string(alias)}")
         end
     end
   end

lib/elixir/test/elixir/typespec_test.exs

@@ -75,6 +75,14 @@ defmodule TypespecTest do
                        @type my_type :: %URI.t(){}
                      end
                    end
+
+      assert_raise Kernel.TypespecError,
+                   ~r"unexpected expression in typespec: t\.Foo",
+                   fn ->
+                     test_module do
+                       @type my_type :: t.Foo
+                     end
+                   end
     end
 
     test "invalid function specification" do
@@ -120,7 +128,7 @@ defmodule TypespecTest do
 
     test "redefined type" do
       assert_raise Kernel.TypespecError,
-                   ~r"type foo/0 is already defined in .*test/elixir/typespec_test.exs:126",
+                   ~r"type foo/0 is already defined in .*test/elixir/typespec_test.exs:134",
                    fn ->
                      test_module do
                        @type foo :: atom
@@ -129,7 +137,7 @@ defmodule TypespecTest do
                    end
 
       assert_raise Kernel.TypespecError,
-                   ~r"type foo/2 is already defined in .*test/elixir/typespec_test.exs:136",
+                   ~r"type foo/2 is already defined in .*test/elixir/typespec_test.exs:144",
                    fn ->
                      test_module do
                        @type foo :: atom
@@ -139,7 +147,7 @@ defmodule TypespecTest do
                    end
 
       assert_raise Kernel.TypespecError,
-                   ~r"type foo/0 is already defined in .*test/elixir/typespec_test.exs:145",
+                   ~r"type foo/0 is already defined in .*test/elixir/typespec_test.exs:153",
                    fn ->
                      test_module do
                        @type foo :: atom
@@ -841,6 +849,19 @@ defmodule TypespecTest do
       assert [{:atom, _, Keyword}, {:atom, _, :t}, [{:var, _, :value}]] = kw_with_value_args
     end
 
+    test "@type with macro in alias" do
+      bytecode =
+        test_module do
+          defmacro module() do
+            quote do: __MODULE__
+          end
+
+          @type my_type :: module().Foo
+        end
+
+      assert [type: {:my_type, {:atom, _, TypespecTest.TypespecSample.Foo}, []}] = types(bytecode)
+    end
+
     test "@type with a reserved signature" do
       assert_raise Kernel.TypespecError,
                    ~r"type required\/1 is a reserved type and it cannot be defined",