Correctly validate number of args for clauses with when in for and catch (#13785)

Author: lukaszsamson

lib/elixir/src/elixir_clauses.erl

@@ -257,6 +257,9 @@ expand_clauses_with_stacktrace(Meta, Fun, Clauses, S, E) ->
   {Ret, SE} = expand_clauses(Meta, 'try', Fun, Clauses, SS, E),
   {Ret, SE#elixir_ex{stacktrace=OldStacktrace}}.
 
+expand_catch(Meta, [{'when', _, [_, _, _, _ | _]}], _, E) ->
+  Error = {wrong_number_of_args_for_clause, "one or two args", origin(Meta, 'try'), 'catch'},
+  file_error(Meta, E, ?MODULE, Error);
 expand_catch(_Meta, [_] = Args, S, E) ->
   head(Args, S, E);
 expand_catch(_Meta, [_, _] = Args, S, E) ->

lib/elixir/src/elixir_expand.erl

@@ -812,6 +812,9 @@ expand_for_do_block(_Meta, Expr, S, E, false) ->
   expand(Expr, S, E);
 expand_for_do_block(Meta, [{'->', _, _} | _] = Clauses, S, E, {reduce, _}) ->
   Transformer = fun
+    ({_, _, [[{'when', _, [_, _, _ | _]}], _]}, _) ->
+      file_error(Meta, E, ?MODULE, for_with_reduce_bad_block);
+
     ({_, _, [[_], _]} = Clause, SA) ->
       SReset = elixir_env:reset_unused_vars(SA),
 

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

@@ -948,6 +948,11 @@ defmodule Kernel.ExpansionTest do
         ~r"when using :reduce with comprehensions, the do block must be written using acc -> expr clauses",
         fn -> expand(quote(do: for(x <- 1..3, reduce: %{}, do: (acc, x -> x)))) end
       )
+
+      assert_compile_error(
+        ~r"when using :reduce with comprehensions, the do block must be written using acc -> expr clauses",
+        fn -> expand(quote(do: for(x <- 1..3, reduce: %{}, do: (acc, x when 1 == 1 -> x)))) end
+      )
     end
 
     test "raise error for unknown options" do
@@ -2130,6 +2135,19 @@ defmodule Kernel.ExpansionTest do
 
         expand(code)
       end)
+
+      assert_compile_error(message, fn ->
+        code =
+          quote do
+            try do
+              x
+            catch
+              _, _, _ when 1 == 1 -> :ok
+            end
+          end
+
+        expand(code)
+      end)
     end
 
     test "expects clauses for rescue, else, catch" do