Do not crash on duplicate bindings, closes #11378

Author: josevalim

lib/elixir/src/elixir.erl

@@ -254,7 +254,7 @@ eval_quoted(Tree, Binding, #{line := Line} = E) ->
 eval_forms(Tree, Binding, Opts) when is_list(Opts) ->
   eval_forms(Tree, Binding, env_for_eval(Opts));
 eval_forms(Tree, RawBinding, OrigE) ->
-  {Vars, Binding} = normalize_binding(RawBinding, [], []),
+  {Vars, Binding} = normalize_binding(RawBinding, [], [], 0),
   E = elixir_env:with_vars(OrigE, Vars),
   {_, S} = elixir_env:env_to_erl(E),
   {Erl, NewErlS, NewExS, NewE} = quoted_to_erl(Tree, E, S),
@@ -275,12 +275,12 @@ eval_forms(Tree, RawBinding, OrigE) ->
       {Value, elixir_erl_var:dump_binding(NewBinding, NewExS, NewErlS), NewE}
   end.
 
-normalize_binding([{Key, Value} | Binding], Vars, Acc) when is_atom(Key) ->
-  normalize_binding(Binding, [{Key, nil} | Vars], [{{Key, nil}, Value} | Acc]);
-normalize_binding([{Pair, Value} | Binding], Vars, Acc) ->
-  normalize_binding(Binding, [Pair | Vars], [{Pair, Value} | Acc]);
-normalize_binding([], Vars, Acc) ->
-  {Vars, Acc}.
+normalize_binding([{Key, Value} | Binding], Vars, Acc, I) when is_atom(Key) ->
+  normalize_binding(Binding, [{{Key, nil}, I} | Vars], [{{Key, nil}, Value} | Acc], I + 1);
+normalize_binding([{Pair, Value} | Binding], Vars, Acc, I) ->
+  normalize_binding(Binding, [{Pair, I} | Vars], [{Pair, Value} | Acc], I + 1);
+normalize_binding([], Vars, Acc, _I) ->
+  {maps:from_list(Vars), Acc}.
 
 recur_eval([Expr | Exprs], Binding, Env) ->
   {value, Value, NewBinding} =

lib/elixir/src/elixir_env.erl

@@ -38,8 +38,7 @@ to_caller(#{} = Env) ->
   Env.
 
 with_vars(Env, Vars) ->
-  {VarVersions, _} = lists:mapfoldl(fun(Var, I) -> {{Var, I}, I + 1} end, 0, Vars),
-  Env#{versioned_vars := maps:from_list(VarVersions)}.
+  Env#{versioned_vars := Vars}.
 
 reset_vars(Env) ->
   Env#{versioned_vars := #{}}.

lib/elixir/test/elixir/code_test.exs

@@ -35,10 +35,6 @@ defmodule CodeTest do
       assert {3, _} = Code.eval_string("a + b", [a: 1, b: 2], __ENV__)
     end
 
-    test "returns bindings from a different context" do
-      assert Code.eval_string("var!(a, Sample) = 1") == {1, [{{:a, Sample}, 1}]}
-    end
-
     test "supports unnamed scopes" do
       assert {%RuntimeError{}, [a: %RuntimeError{}]} =
                Code.eval_string("a = (try do (raise \"hello\") rescue e -> e end)")
@@ -48,6 +44,16 @@ defmodule CodeTest do
       assert Code.eval_string("Kernel.if true, do: :ok", [], requires: [Z, Kernel]) == {:ok, []}
     end
 
+    test "returns bindings from a different context" do
+      assert Code.eval_string("var!(a, Sample) = 1") == {1, [{{:a, Sample}, 1}]}
+    end
+
+    test "does not raise on duplicate bindings" do
+      # The order of which values win is not guaranteed, but it should evaluate successfully.
+      assert Code.eval_string("b = String.Chars.to_string(a)", a: 0, a: 1) ==
+               {"1", [{:b, "1"}, {:a, 1}]}
+    end
+
     test "with many options" do
       options = [
         functions: [{Kernel, [is_atom: 1]}],