From 6aca6560022f22d2ab0dc4de0724387b035f040f Mon Sep 17 00:00:00 2001
From: Lukasz Samson <lukaszsamson@gmail.com>
Date: Thu, 26 Sep 2024 23:42:08 +0200
Subject: [PATCH] do not infer special forms as local calls

---
 lib/elixir_sense/core/type_inference.ex       | 48 ++++++++++++++++
 .../elixir_sense/core/type_inference_test.exs | 55 +++++++++++++++++++
 2 files changed, 103 insertions(+)

diff --git a/lib/elixir_sense/core/type_inference.ex b/lib/elixir_sense/core/type_inference.ex
index 26a02804..e31a1fbc 100644
--- a/lib/elixir_sense/core/type_inference.ex
+++ b/lib/elixir_sense/core/type_inference.ex
@@ -167,6 +167,54 @@ defmodule ElixirSense.Core.TypeInference do
     {:list, list |> Enum.map(&type_of(&1, context))}
   end
 
+  # block expressions
+  def type_of({:__block__, _meta, exprs}, context) do
+    case List.last(exprs) do
+      nil -> nil
+      last_expr -> type_of(last_expr, context)
+    end
+  end
+
+  # anonymous functions
+  def type_of({:fn, _meta, _clauses}, _context), do: nil
+
+  # special forms
+  # for case/cond/with/receive/for/try we have no idea what the type is going to be
+  # we don't support binaries
+  # TODO guard?
+  # other are not worth handling
+  def type_of({form, _meta, _clauses}, _context)
+      when form in [
+             :case,
+             :cond,
+             :try,
+             :receive,
+             :for,
+             :with,
+             :quote,
+             :unquote,
+             :unquote_splicing,
+             :import,
+             :alias,
+             :require,
+             :__aliases__,
+             :__cursor__,
+             :__DIR__,
+             :super,
+             :<<>>,
+             :"::"
+           ],
+      do: nil
+
+  # __ENV__ is already expanded to map
+  def type_of({form, _meta, _clauses}, _context) when form in [:__CALLER__] do
+    {:struct, [], {:atom, Macro.Env}, nil}
+  end
+
+  def type_of({:__STACKTRACE__, _meta, _clauses}, _context) do
+    {:list, nil}
+  end
+
   # local call
   def type_of({var, _, args}, context) when is_atom(var) and is_list(args) do
     {:local_call, var, Enum.map(args, &type_of(&1, context))}
diff --git a/test/elixir_sense/core/type_inference_test.exs b/test/elixir_sense/core/type_inference_test.exs
index 5059395c..ca63badb 100644
--- a/test/elixir_sense/core/type_inference_test.exs
+++ b/test/elixir_sense/core/type_inference_test.exs
@@ -488,5 +488,60 @@ defmodule ElixirSense.Core.TypeInferenceTest do
       assert type_of("\"asd\"") == nil
       assert type_of("1.23") == nil
     end
+
+    test "__STACKTRACE__ returns {:list, nil}" do
+      assert type_of("__STACKTRACE__") == {:list, nil}
+    end
+
+    test "anonymous function returns nil" do
+      assert type_of("fn -> a end") == nil
+      assert type_of("fn x -> x + 1 end") == nil
+      assert type_of("fn x, y -> x * y end") == nil
+    end
+  end
+
+  describe "block expressions" do
+    test "non-empty block returns type of last expression" do
+      assert type_of("(a = 1; b = 2; c = 3)") == {:integer, 3}
+
+      assert type_of("""
+               (
+                 a = 1
+                 b = 2
+                 c = 3
+               )
+             """) == {:integer, 3}
+    end
+
+    test "empty block returns nil" do
+      assert type_of("( )") == nil
+    end
+
+    test "__CALLER__ returns {:struct, [], {:atom, Macro.Env}, nil}" do
+      assert type_of("__CALLER__") == {:struct, [], {:atom, Macro.Env}, nil}
+    end
+  end
+
+  describe "special forms" do
+    special_forms = [
+      "case a do\n  :ok -> 1\n  :error -> 2\nend",
+      "cond do\n  a -> 1\n  b -> 2\nend",
+      "try do\n  risky_operation()\nrescue\n  e -> handle(e)\nend",
+      "receive do\n  {:msg, msg} -> process(msg)\nend",
+      "for x <- list, do: x * 2",
+      "with {:ok, a} <- fetch_a(), {:ok, b} <- fetch_b(a), do: a + b",
+      "quote do: a + b",
+      "unquote(expr)",
+      "unquote_splicing(expr)",
+      "import Module",
+      "alias Module.SubModule",
+      "require Module"
+    ]
+
+    for form <- special_forms do
+      test "special form: #{inspect(form)} returns nil" do
+        assert type_of(unquote(form)) == nil
+      end
+    end
   end
 end