Do not crash on preemptive errors with static atoms encoder, closes #13927

Author: josevalim

lib/elixir/src/elixir_tokenizer.erl

@@ -1364,7 +1364,7 @@ interpolation_format({_, _, _} = Reason, _Extension, _Args, _Line, _Column, _Ope
 
 %% Terminators
 
-handle_terminator(Rest, _, _, Scope, {'(', {Line, Column, _}}, [{alias, _, Alias} | Tokens]) ->
+handle_terminator(Rest, _, _, Scope, {'(', {Line, Column, _}}, [{alias, _, Alias} | Tokens]) when is_atom(Alias) ->
   Reason =
     io_lib:format(
       "unexpected ( after alias ~ts. Function names and identifiers in Elixir "

lib/elixir/test/elixir/kernel/parser_test.exs

@@ -345,6 +345,16 @@ defmodule Kernel.ParserTest do
                 {[line: 1, column: 1], "atom length must be less than system limit: ", atom}}
     end
 
+    test "avoids crashes on invalid AST" do
+      encoder = fn atom, _meta -> {:ok, {:atom, [], [atom]}} end
+
+      assert {:error, {_, "missing terminator: )", ""}} =
+               Code.string_to_quoted("Module(", static_atoms_encoder: encoder)
+
+      assert {:error, {_, "syntax error before: ", "'('"}} =
+               Code.string_to_quoted("Module()", static_atoms_encoder: encoder)
+    end
+
     test "may return errors" do
       encoder = fn _atom, _meta ->
         {:error, "Invalid atom name"}