Fix mypy dependencies

mypy-0.780.nix

@@ -2,17 +2,24 @@
   lib,
   fetchFromGitHub,
   python3,
+  # Injected dependencies
+  mypy-extensions,
+  typed-ast,
 }:
 
-python3.pkgs.buildPythonPackage rec {
+# mypy 0.780 is the last version with --py2 support
+# Built without mypyc so mycpp can extend its classes
+python3.pkgs.buildPythonPackage (finalAttrs: {
   pname = "mypy";
-  # This is the version oils-for-unix uses for mycpp Python-to-C++ translation
   version = "0.780";
 
+  pyproject = true;
+  build-system = [ python3.pkgs.setuptools ];
+
   src = fetchFromGitHub {
     owner = "python";
     repo = "mypy";
-    rev = "v${version}";
+    rev = "v${finalAttrs.version}";
     # Fetch submodules to include typeshed (required for type stubs)
     fetchSubmodules = true;
     hash = "sha256-czwCx6ZjCu3CrVmbI6NbstzWM0GvuPTWJiiUhXSznu4=";
@@ -27,14 +34,18 @@ python3.pkgs.buildPythonPackage rec {
   # Skip tests to speed up build
   doCheck = false;
 
-  dependencies = with python3.pkgs; [
+  # Skip runtime dependency check since we're using pinned older versions
+  pythonRuntimeDepsCheck = false;
+  dontCheckRuntimeDeps = true;
+
+  dependencies = [
     mypy-extensions
-    typing-extensions
     typed-ast
+    python3.pkgs.typing-extensions
   ];
 
   # Ensure we're not pulling in a compiled version
   pythonImportsCheck = [ "mypy" ];
 
   meta.license = lib.licenses.mit;
-}
+})