fix typing issue around lru_cache arguments (#2098)

This was found by python/mypy#10308

diff --git a/src/black/__init__.py b/src/black/__init__.py
index 0065beafe0e57912db60229e6da863a8575a8ce7..2bb42a470eadb617b3cb57c4ee4b9c0c76377d40 100644 (file)
--- a/src/black/__init__.py
+++ b/src/black/__init__.py
@@ -302,7 +302,7 @@ def supports_feature(target_versions: Set[TargetVersion], feature: Feature) -> b
     return all(feature in VERSION_TO_FEATURES[version] for version in target_versions)
 
 
-def find_pyproject_toml(path_search_start: Iterable[str]) -> Optional[str]:
+def find_pyproject_toml(path_search_start: Tuple[str, ...]) -> Optional[str]:
     """Find the absolute filepath to a pyproject.toml if it exists"""
     path_project_root = find_project_root(path_search_start)
     path_pyproject_toml = path_project_root / "pyproject.toml"
@@ -6214,7 +6214,7 @@ def gen_python_files(
 
 
 @lru_cache()
-def find_project_root(srcs: Iterable[str]) -> Path:
+def find_project_root(srcs: Tuple[str, ...]) -> Path:
     """Return a directory containing .git, .hg, or pyproject.toml.
 
     That directory will be a common parent of all files and directories