Remove unsupported matching on rescue clause

Author: José Valim

lib/elixir/src/elixir_try.erl

@@ -49,7 +49,6 @@ each_clause(Meta, { rescue, [Condition|T], Expr }, S) ->
           end
       end;
     _ ->
-      validate_rescue_access(Meta, Condition, S),
       each_clause(Meta, { 'catch', [error, Condition|T], Expr }, S)
   end;
 
@@ -65,8 +64,12 @@ each_clause(Meta, {Key,_,_}, S) ->
 normalize_rescue(Meta, List, S) when is_list(List) ->
   normalize_rescue(Meta, { in, Meta, [{ '_', Meta, nil }, List] }, S);
 
+%% rescue _
+normalize_rescue(_, { '_', _, Atom }, _S) when is_atom(Atom) ->
+  false;
+
 %% rescue var -> var in _
-normalize_rescue(_, { Name, Meta, Atom } = Rescue, S) when is_atom(Name), is_atom(Atom), Name /= '_' ->
+normalize_rescue(_, { Name, Meta, Atom } = Rescue, S) when is_atom(Name), is_atom(Atom) ->
   normalize_rescue(Meta, { in, Meta, [Rescue, { '_', Meta, nil }] }, S);
 
 %% rescue var in [Exprs]
@@ -85,22 +88,13 @@ normalize_rescue(_, { in, Meta, [Left, Right] }, S) ->
       end
   end;
 
-normalize_rescue(_, { '=', Meta, [{ '__aliases__', _, _ } = Alias, { Name, _, Atom } = Var] }, S)
-    when is_atom(Name) and is_atom(Atom) ->
-  elixir_errors:handle_file_warning(S#elixir_scope.file, { Meta, ?MODULE, { rescue_no_match, Var, Alias } }),
-  false;
-
-normalize_rescue(_, { '=', Meta, [{ Name, _, Atom } = Var, { '__aliases__', _, _ } = Alias] }, S)
-    when is_atom(Name) and is_atom(Atom) ->
-  elixir_errors:handle_file_warning(S#elixir_scope.file, { Meta, ?MODULE, { rescue_no_match, Var, Alias } }),
-  false;
-
 normalize_rescue(Meta, Condition, S) ->
   case elixir_translator:translate_each(Condition, S#elixir_scope{context=match}) of
     { { atom, _, Atom }, _ } ->
       normalize_rescue(Meta, { in, Meta, [{ '_', Meta, nil }, [Atom]] }, S);
     _ ->
-      false
+      elixir_errors:syntax_error(Meta, S#elixir_scope.file, "invalid rescue clause. The clause should match on an alias, "
+        "a variable or be in the `var in [alias]` format")
   end.
 
 %% Convert rescue clauses into guards.
@@ -242,24 +236,6 @@ erlang_rescue_guard_for(Meta, Var, 'Elixir.ErlangError') ->
   ] },
   { 'or', Meta, [IsNotTuple, IsException] }.
 
-%% Validate rescue access
-
-validate_rescue_access(Meta, { '=', _, [Left, Right] }, S) ->
-  validate_rescue_access(Meta, Left, S),
-  validate_rescue_access(Meta, Right, S);
-
-validate_rescue_access(Meta, { { '.', _, ['Elixir.Kernel', 'access'] }, _, [Element, _] }, S) ->
-  case elixir_translator:translate_each(Element, S) of
-    { { atom, _, Atom }, _ } ->
-      case lists:member(Atom, erlang_rescues()) of
-        false -> [];
-        true -> elixir_errors:syntax_error(Meta, S#elixir_scope.file, "cannot (yet) pattern match against erlang exceptions")
-      end;
-    _ -> []
-  end;
-
-validate_rescue_access(_, _, _) -> [].
-
 %% Helpers
 
 format_error({ rescue_no_match, Var, Alias }) ->

lib/elixir/test/elixir/kernel/errors_test.exs

@@ -229,8 +229,8 @@ defmodule Kernel.ErrorsTest do
       format_rescue 'Kernel.ErrorsTest.Config[foo: :bar]'
   end
 
-  test :invalid_access_protocol_on_rescue do
-    assert "nofile:1: cannot (yet) pattern match against erlang exceptions" ==
+  test :invalid_rescue_clause do
+    assert "nofile:1: invalid rescue clause. The clause should match on an alias, a variable or be in the `var in [alias]` format" ==
       format_rescue 'try do\n1\nrescue\nUndefinedFunctionError[arity: 1] -> false\nend'
   end
 

lib/elixir/test/elixir/kernel/rescue_test.exs

@@ -93,18 +93,6 @@ defmodule Kernel.RescueTest do
     assert result == "an exception"
   end
 
-  test :rescue_defined_variable do
-    var = Protocol.UndefinedError[protocol: Foo]
-
-    result = try do
-      raise Protocol.UndefinedError, protocol: Foo
-    rescue
-      ^var -> true
-    end
-
-    assert result, "Expected to rescue with success"
-  end
-
   test :rescue_named_defined_variable do
     expected = RuntimeError
 
@@ -262,16 +250,5 @@ defmodule Kernel.RescueTest do
     assert result == "undefined function: DoNotExist.for_sure/0"
   end
 
-  test :pattern_matching do
-    result = try do
-      raise Protocol.UndefinedError, protocol: Foo
-    rescue
-      Protocol.UndefinedError[protocol: Bar] -> false
-      Protocol.UndefinedError[protocol: Foo] = x -> x.message
-    end
-
-    assert result == "protocol Foo not implemented for nil"
-  end
-
   defp zero(0), do: 0
 end