Raise on missing struct for module conflict, closes #12113

Author: josevalim

lib/elixir/src/elixir_map.erl

@@ -138,13 +138,19 @@ load_struct(Meta, Name, Args, Keys, E) ->
 wrapped_load_struct(Meta, Name, Args, Keys, E) ->
   %% We also include the current module because it won't be present
   %% in context module in case the module name is defined dynamically.
-  InContext = lists:member(Name, [?key(E, module) | ?key(E, context_modules)]),
+  Module = ?key(E, module),
+  InContext = lists:member(Name, [Module | ?key(E, context_modules)]),
 
   Arity = length(Args),
   External = InContext orelse (not(ensure_loaded(Name)) andalso wait_for_struct(Name)),
 
   try
     case External andalso elixir_def:external_for(Meta, Name, '__struct__', Arity, [def]) of
+      %% If I am accessing myself and there is no __struct__ function,
+      %% don't invoke the fallback to avoid calling loaded code.
+      false when Module == Name ->
+        error(undef);
+
       false ->
         apply(Name, '__struct__', Args);
 

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

@@ -204,6 +204,23 @@ defmodule Kernel.ErrorsTest do
       end
     end
 
+    test "bad struct on module conflict" do
+      Code.put_compiler_option(:ignore_module_conflict, true)
+
+      assert_eval_raise CompileError, ~r'MissingStructOnReload\.__struct__/1 is undefined', ~c'''
+      defmodule MissingStructOnReload do
+        defstruct [:title]
+        def d(), do: %MissingStructOnReload{}
+      end
+
+      defmodule MissingStructOnReload do
+        def d(), do: %MissingStructOnReload{}
+      end
+      '''
+    after
+      Code.put_compiler_option(:ignore_module_conflict, false)
+    end
+
     test "missing struct key" do
       missing_struct_key_error =
         ~r"expected Kernel.ErrorsTest.MissingStructKey.__struct__/(0|1) to return a map.*, got: %\{\}"