Support generated: true in quote

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

Author: José Valim

lib/elixir/lib/kernel/special_forms.ex

@@ -765,6 +765,10 @@ defmodule Kernel.SpecialForms do
       quote. Read the Stacktrace information section below for more
       information.
 
+    * `:generated` - marks the given chunk as generated so it does not emit warnings.
+      Currently it only works on special forms (for example, you cannot annotate
+      a `case` but not an `if`).
+
     * `:context` - sets the resolution context.
 
     * `:bind_quoted` - passes a binding to the macro. Whenever a binding is

lib/elixir/src/elixir.hrl

@@ -29,7 +29,8 @@
   imports_hygiene=true,
   unquote=true,
   unquoted=false,
-  escape=false
+  escape=false,
+  generated=false
 }).
 
 -record(elixir_tokenizer, {

lib/elixir/src/elixir_exp.erl

@@ -157,7 +157,7 @@ expand({quote, Meta, [KV, Do]}, E) when is_list(Do) ->
       false -> compile_error(Meta, E#elixir_scope.file, "missing do keyword in quote")
     end,
 
-  ValidOpts = [context, location, line, file, unquote, bind_quoted],
+  ValidOpts = [context, location, line, file, unquote, bind_quoted, generated],
   {EKV, ET} = expand_opts(Meta, quote, ValidOpts, KV, E),
 
   Context = case lists:keyfind(context, 1, EKV) of
@@ -198,7 +198,13 @@ expand({quote, Meta, [KV, Do]}, E) when is_list(Do) ->
     false -> DefaultUnquote
   end,
 
-  Q = #elixir_quote{line=Line, file=File, unquote=Unquote, context=Context},
+  Generated = lists:keyfind(generated, 1, EKV) == {generated, true},
+
+  %% TODO: Do not allow negative line numbers once Erlang 18
+  %% support is dropped as it only allows negative line
+  %% annotations alongside the generated check.
+  Q = #elixir_quote{line=Line, file=File, unquote=Unquote,
+                    context=Context, generated=Generated},
 
   {Quoted, _Q} = elixir_quote:quote(Exprs, Binding, Q, ET),
   expand(Quoted, ET);

lib/elixir/src/elixir_quote.erl

@@ -321,7 +321,10 @@ do_quote_tuple({Left, Meta, Right}, Q, E) ->
   {{'{}', [], [TLeft, meta(Meta, Q), TRight]}, RQ}.
 
 meta(Meta, Q) ->
-  file(line(Meta, Q), Q).
+  generated(file(line(Meta, Q), Q), Q).
+
+generated(Meta, #elixir_quote{generated=true}) -> [{generated, true}|Meta];
+generated(Meta, #elixir_quote{generated=false}) -> Meta.
 
 file(Meta, #elixir_quote{file=nil}) -> Meta;
 file(Meta, #elixir_quote{file=File}) -> [{file, File}|Meta].

lib/elixir/test/elixir/kernel/quote_test.exs

@@ -27,6 +27,10 @@ defmodule Kernel.QuoteTest do
     assert quote(line: line, do: bar(1, 2, 3)) == {:bar, [line: 26], [1, 2, 3]}
   end
 
+  test "generated" do
+    assert quote(generated: true, do: bar(1)) == {:bar, [generated: true], [1]}
+  end
+
   test "unquote call" do
     assert quote(do: foo(bar)[unquote(:baz)]) == quote(do: foo(bar)[:baz])
     assert quote(do: unquote(:bar)()) == quote(do: bar())
@@ -216,7 +220,7 @@ defmodule Kernel.QuoteTest.ErrorsTest do
 
     mod  = Kernel.QuoteTest.ErrorsTest
     file = __ENV__.file |> Path.relative_to_cwd |> String.to_char_list
-    assert [{^mod, :add, 2, [file: ^file, line: 196]}|_] = System.stacktrace
+    assert [{^mod, :add, 2, [file: ^file, line: 200]}|_] = System.stacktrace
   end
 
   test "outside function error" do
@@ -226,7 +230,7 @@ defmodule Kernel.QuoteTest.ErrorsTest do
 
     mod  = Kernel.QuoteTest.ErrorsTest
     file = __ENV__.file |> Path.relative_to_cwd |> String.to_char_list
-    assert [{^mod, _, _, [file: ^file, line: 224]}|_] = System.stacktrace
+    assert [{^mod, _, _, [file: ^file, line: 228]}|_] = System.stacktrace
   end
 end