Do not expand bind_quoted expressions twice

Author: josevalim

lib/elixir/src/elixir_expand.erl

@@ -207,9 +207,14 @@ expand({quote, Meta, [Opts, Do]}, S, E) when is_list(Do) ->
   Unquote = proplists:get_value(unquote, EOpts, DefaultUnquote),
   Generated = proplists:get_value(generated, EOpts, false),
 
-  {Q, Prelude} = elixir_quote:build(Meta, Line, File, Context, Unquote, Generated, ET),
-  Quoted = elixir_quote:quote(Meta, Exprs, Binding, Q, Prelude),
-  expand(Quoted, ST, ET);
+  {Q, EBinding, Prelude} = elixir_quote:build(Meta, Line, File, Context, Unquote, Generated, Binding, ET),
+  Quoted = elixir_quote:quote(Exprs, Q, Prelude),
+  {EQuoted, ES, EQ} = expand(Quoted, ST, ET),
+
+  case EBinding of
+    [] -> {EQuoted, ES, EQ};
+     _ -> {{'{}', [], ['__block__', [], EBinding ++ [EQuoted]]}, ES, EQ}
+  end;
 
 expand({quote, Meta, [_, _]}, _S, E) ->
   file_error(Meta, E, ?MODULE, {invalid_args, 'quote'});

lib/elixir/src/elixir_quote.erl

@@ -1,5 +1,5 @@
 -module(elixir_quote).
--export([escape/3, linify/3, linify_with_context_counter/3, build/7, quote/5, has_unquotes/1, fun_to_quoted/1]).
+-export([escape/3, linify/3, linify_with_context_counter/3, build/8, quote/3, has_unquotes/1, fun_to_quoted/1]).
 -export([dot/5, tail_list/3, list/2, validate_runtime/2]). %% Quote callbacks
 
 -include("elixir.hrl").
@@ -200,7 +200,7 @@ bad_escape(Arg) ->
 
 %% Quote entry points
 
-build(Meta, Line, File, Context, Unquote, Generated, E) ->
+build(Meta, Line, File, Context, Unquote, Generated, Binding, E) ->
   Acc0 = [],
   {ELine, Acc1} = validate_compile(Meta, line, Line, Acc0),
   {EFile, Acc2} = validate_compile(Meta, file, File, Acc1),
@@ -219,7 +219,15 @@ build(Meta, Line, File, Context, Unquote, Generated, E) ->
     generated=Generated
   },
 
-  {Q, Acc3}.
+  Vars =
+    [{'{}', [],
+      ['=', [], [
+        {'{}', [], [K, Meta, EContext]},
+        V
+      ]
+     ]} || {K, V} <- Binding],
+
+  {Q, Vars, Acc3}.
 
 validate_compile(_Meta, line, Value, Acc) when is_boolean(Value) ->
   {Value, Acc};
@@ -255,30 +263,16 @@ is_valid(context, Context) -> is_atom(Context) andalso (Context /= nil);
 is_valid(generated, Generated) -> is_boolean(Generated);
 is_valid(unquote, Unquote) -> is_boolean(Unquote).
 
-quote(_Meta, {unquote_splicing, _, [_]}, _Binding, #elixir_quote{unquote=true}, _) ->
+quote({unquote_splicing, _, [_]}, #elixir_quote{unquote=true}, _) ->
   argument_error(<<"unquote_splicing only works inside arguments and block contexts, "
     "wrap it in parens if you want it to work with one-liners">>);
 
-quote(Meta, Expr, Binding, Q, Prelude) ->
-  Context = Q#elixir_quote.context,
-
-  Vars = [{'{}', [],
-    ['=', [], [
-      {'{}', [], [K, Meta, Context]},
-      V
-    ]]
-  } || {K, V} <- Binding],
-
+quote(Expr, Q, Prelude) ->
   Quoted = do_quote(Expr, Q),
 
-  WithVars = case Vars of
-    [] -> Quoted;
-    _ -> {'{}', [], ['__block__', [], Vars ++ [Quoted]]}
-  end,
-
   case Prelude of
-    [] -> WithVars;
-    _ -> {'__block__', [], Prelude ++ [WithVars]}
+    [] -> Quoted;
+    _ -> {'__block__', [], Prelude ++ [Quoted]}
   end.
 
 %% quote/unquote

lib/elixir/test/elixir/kernel/expansion_test.exs

@@ -621,6 +621,23 @@ defmodule Kernel.ExpansionTest do
       assert expand(quote(do: quote(do: hello)), []) == {:{}, [], [:hello, [], __MODULE__]}
     end
 
+    test "expand bind_quoted once" do
+      expand_env(
+        quote do
+          var = 123
+          quote(bind_quoted: [var: var], do: var)
+        end,
+        __ENV__,
+        []
+      )
+      |> elem(0)
+      |> Macro.prewalk(fn
+        {:var, [version: 0], Kernel.ExpansionTest} -> :ok
+        {:var, _, Kernel.ExpansionTest} = invalid -> flunk("unexpected node #{inspect(invalid)}")
+        node -> node
+      end)
+    end
+
     test "raises if the :bind_quoted option is invalid" do
       assert_compile_error(~r"invalid :bind_quoted for quote", fn ->
         expand(quote(do: quote(bind_quoted: self(), do: :ok)))