Do not attempt to group module warnings with context

Otherwise, the larger the context, the more expensive
grouping the warnings would get.

Closes #13742

lib/elixir/lib/module/parallel_checker.ex

@@ -291,18 +291,34 @@ defmodule Module.ParallelChecker do
   ## Warning helpers
 
   defp group_warnings(warnings) do
-    warnings
-    |> Enum.reduce(%{}, fn {module, warning, location}, acc ->
-      locations = MapSet.new([location])
-      Map.update(acc, {module, warning}, locations, &MapSet.put(&1, location))
-    end)
-    |> Enum.map(fn {{module, warning}, locations} -> {module, warning, Enum.sort(locations)} end)
-    |> Enum.sort()
+    {ungrouped, grouped} =
+      Enum.reduce(warnings, {[], %{}}, fn {module, warning, location}, {ungrouped, grouped} ->
+        %{message: _} = diagnostic = module.format_diagnostic(warning)
+
+        if Map.get(diagnostic, :group, false) do
+          locations = MapSet.new([location])
+
+          grouped =
+            Map.update(grouped, warning, {locations, diagnostic}, fn
+              {locations, diagnostic} -> {MapSet.put(locations, location), diagnostic}
+            end)
+
+          {ungrouped, grouped}
+        else
+          {[{[location], diagnostic} | ungrouped], grouped}
+        end
+      end)
+
+    grouped =
+      Enum.map(grouped, fn {_warning, {locations, diagnostic}} ->
+        {Enum.sort(locations), diagnostic}
+      end)
+
+    Enum.sort(ungrouped ++ grouped)
   end
 
   defp emit_warnings(warnings, log?) do
-    Enum.flat_map(warnings, fn {module, warning, locations} ->
-      %{message: _} = diagnostic = module.format_diagnostic(warning)
+    Enum.flat_map(warnings, fn {locations, diagnostic} ->
       diagnostics = Enum.map(locations, &to_diagnostic(diagnostic, &1))
       log? and print_diagnostics(diagnostics)
       diagnostics

lib/elixir/lib/module/types/of.ex

@@ -700,14 +700,16 @@ defmodule Module.Types.Of do
           " is undefined (module ",
           inspect(module),
           " is not available or is yet to be defined)"
-        ])
+        ]),
+      group: true
     }
   end
 
   def format_diagnostic({:undefined_function, module, :__struct__, 0, _exports}) do
     %{
       message:
-        "struct #{inspect(module)} is undefined (there is such module but it does not define a struct)"
+        "struct #{inspect(module)} is undefined (there is such module but it does not define a struct)",
+      group: true
     }
   end
 
@@ -718,7 +720,8 @@ defmodule Module.Types.Of do
           Exception.format_mfa(module, fun, arity),
           " is undefined or private",
           UndefinedFunctionError.hint_for_loaded_module(module, fun, arity, exports)
-        ])
+        ]),
+      group: true
     }
   end
 
@@ -729,7 +732,8 @@ defmodule Module.Types.Of do
           Exception.format_mfa(module, fun, arity),
           " is deprecated. ",
           reason
-        ])
+        ]),
+      group: true
     }
   end
 
@@ -741,7 +745,8 @@ defmodule Module.Types.Of do
           inspect(module),
           " before invoking the macro ",
           Exception.format_mfa(module, fun, arity)
-        ])
+        ]),
+      group: true
     }
   end