From 04c67da5b455416c71fe9bc4c70fe61ceb7aad79 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= <bjorn@erlang.org>
Date: Tue, 16 Aug 2016 14:19:59 +0200
Subject: erl_internal: Add add_predefined_functions/1

The sys_pre_expand module used to do a lot more (translate records and
funs, for example), but now it does very little. Most of the code is
an identify transformation of the abstract format.

The identity transformation part of the code must be maintained and
kept correct when new forms are added to the abstract format. That
adds to the maintance burden. It also adds (slightly) to compilation
times.  Therefore, we want to eliminate sys_pre_expand, moving all of
its (non-identity) transformations to better places.

As a preliminary first step, move the code that adds the pre-defined
functions (such as module_info/0) to a new function in erl_internal.
---
 lib/stdlib/doc/src/erl_internal.xml | 10 ++++++
 lib/stdlib/src/erl_internal.erl     | 67 +++++++++++++++++++++++++++++++++++++
 2 files changed, 77 insertions(+)

diff --git a/lib/stdlib/doc/src/erl_internal.xml b/lib/stdlib/doc/src/erl_internal.xml
index cf49df0972..17cd0fb240 100644
--- a/lib/stdlib/doc/src/erl_internal.xml
+++ b/lib/stdlib/doc/src/erl_internal.xml
@@ -43,6 +43,16 @@
   </description>
 
   <funcs>
+    <func>
+      <name name="add_predefined_functions" arity="1"/>
+      <fsummary>Add code for pre-defined functions.</fsummary>
+      <desc>
+        <p>Adds to <c><anno>Forms</anno></c> the code for the standard
+        pre-defined functions (such as <c>module_info/0</c>) that are
+        to be included in every module.</p>
+      </desc>
+    </func>
+
     <func>
       <name name="arith_op" arity="2"/>
       <fsummary>Test for an arithmetic operator.</fsummary>
diff --git a/lib/stdlib/src/erl_internal.erl b/lib/stdlib/src/erl_internal.erl
index 46059f42a5..5d6aa0ebe8 100644
--- a/lib/stdlib/src/erl_internal.erl
+++ b/lib/stdlib/src/erl_internal.erl
@@ -54,6 +54,8 @@
 
 -export([is_type/2]).
 
+-export([add_predefined_functions/1]).
+
 %%---------------------------------------------------------------------------
 
 %%  Erlang builtin functions allowed in guards.
@@ -569,3 +571,68 @@ is_type(term, 0) -> true;
 is_type(timeout, 0) -> true;
 is_type(tuple, 0) -> true;
 is_type(_, _) -> false.
+
+%%%
+%%% Add and export the pre-defined functions:
+%%%
+%%%   module_info/0
+%%%   module_info/1
+%%%   behaviour_info/1 (optional)
+%%%
+
+-spec add_predefined_functions(Forms) -> UpdatedForms when
+      Forms :: [erl_parse:abstract_form() | erl_parse:form_info()],
+      UpdatedForms :: [erl_parse:abstract_form() | erl_parse:form_info()].
+
+add_predefined_functions(Forms) ->
+    Forms ++ predefined_functions(Forms).
+
+predefined_functions(Forms) ->
+    Attrs = [{Name,Val} || {attribute,_,Name,Val} <- Forms],
+    {module,Mod} = lists:keyfind(module, 1, Attrs),
+    Callbacks = [Callback || {callback,Callback} <- Attrs],
+    OptionalCallbacks = get_optional_callbacks(Attrs),
+    Mpf1 = module_predef_func_beh_info(Callbacks, OptionalCallbacks),
+    Mpf2 = module_predef_funcs_mod_info(Mod),
+    Mpf = [erl_parse:new_anno(F) || F <- Mpf1++Mpf2],
+    Exp = [{F,A} || {function,_,F,A,_} <- Mpf],
+    [{attribute,0,export,Exp}|Mpf].
+
+get_optional_callbacks(Attrs) ->
+    L = [O || {optional_callbacks,O} <- Attrs, is_fa_list(O)],
+    lists:append(L).
+
+is_fa_list([{FuncName, Arity}|L])
+  when is_atom(FuncName), is_integer(Arity), Arity >= 0 ->
+    is_fa_list(L);
+is_fa_list([]) -> true;
+is_fa_list(_) -> false.
+
+module_predef_func_beh_info([], _) ->
+    [];
+module_predef_func_beh_info(Callbacks0, OptionalCallbacks) ->
+    Callbacks = [FA || {{_,_}=FA,_} <- Callbacks0],
+    List = make_list(Callbacks),
+    OptionalList = make_list(OptionalCallbacks),
+    [{function,0,behaviour_info,1,
+      [{clause,0,[{atom,0,callbacks}],[],[List]},
+       {clause,0,[{atom,0,optional_callbacks}],[],[OptionalList]}]}].
+
+make_list([]) -> {nil,0};
+make_list([{Name,Arity}|Rest]) ->
+    {cons,0,
+     {tuple,0,
+      [{atom,0,Name},
+       {integer,0,Arity}]},
+     make_list(Rest)}.
+
+module_predef_funcs_mod_info(Mod) ->
+    ModAtom = {atom,0,Mod},
+    [{function,0,module_info,0,
+      [{clause,0,[],[],
+        [{call,0,{remote,0,{atom,0,erlang},{atom,0,get_module_info}},
+          [ModAtom]}]}]},
+     {function,0,module_info,1,
+      [{clause,0,[{var,0,'X'}],[],
+        [{call,0,{remote,0,{atom,0,erlang},{atom,0,get_module_info}},
+          [ModAtom,{var,0,'X'}]}]}]}].
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