Address ambiguity on type violation in nested ||

Author: josevalim

lib/elixir/lib/module/types/pattern.ex

@@ -1430,8 +1430,16 @@ defmodule Module.Types.Pattern do
                     #{to_quoted_string(type) |> indent(4)}
                 """
               else
+                additional =
+                  with {:case, meta, [_, _]} <- expr,
+                       {:case, :||} <- meta[:type_check] do
+                    "(shown as ... below) "
+                  else
+                    _ -> ""
+                  end
+
                 """
-                the right-hand side of || will never be executed:
+                the right-hand side of || #{additional}will never be executed:
 
                     #{expr_to_string({:||, [], [expr, {:..., [], []}]}) |> indent(4)}
 

lib/elixir/test/elixir/module/types/expr_test.exs

@@ -1963,6 +1963,17 @@ defmodule Module.Types.ExprTest do
 
              """
 
+      assert typeerror!([x = 123], System.get_env("foo") || x || true) =~ """
+             the right-hand side of || (shown as ... below) will never be executed:
+
+                 System.get_env("foo") || x || ...
+
+             because the left-hand side always evaluates to:
+
+                 dynamic(binary() or integer())
+
+             """
+
       assert typeerror!([x = false], x || true) =~ """
              the following conditional expression will never succeed: