Type fixes

src/pip/_internal/locations/__init__.py

@@ -131,8 +131,16 @@ def get_prefixed_libs(prefix):
     """Return the lib locations under ``prefix``."""
     old_pure, old_plat = _distutils.get_prefixed_libs(prefix)
     new_pure, new_plat = _sysconfig.get_prefixed_libs(prefix)
-    _warn_if_mismatch(old_pure, new_pure, key="prefixed-purelib")
-    _warn_if_mismatch(old_plat, new_plat, key="prefixed-platlib")
+    _warn_if_mismatch(
+        pathlib.Path(old_pure),
+        pathlib.Path(new_pure),
+        key="prefixed-purelib",
+    )
+    _warn_if_mismatch(
+        pathlib.Path(old_plat),
+        pathlib.Path(new_plat),
+        key="prefixed-platlib",
+    )
     if old_pure == old_plat:
         return [old_pure]
     return [old_pure, old_plat]

src/pip/_internal/locations/_sysconfig.py

@@ -18,7 +18,7 @@
 
 
 def _infer_scheme(variant):
-    # (typing.Literal["home", "prefix", "user"]) -> str
+    # type: (typing.Literal["home", "prefix", "user"]) -> str
     """Try to find a scheme for the current platform.
 
     Unfortunately ``_get_default_scheme()`` is private, so there's no way to
@@ -46,16 +46,16 @@ def _infer_scheme(variant):
 
 
 # Update these keys if the user sets a custom home.
-_HOME_KEYS = (
+_HOME_KEYS = [
     "installed_base",
     "base",
     "installed_platbase",
     "platbase",
     "prefix",
     "exec_prefix",
-)
+]
 if sysconfig.get_config_var("userbase") is not None:
-    _HOME_KEYS += ("userbase",)
+    _HOME_KEYS.append("userbase")
 
 
 def get_scheme(
@@ -86,11 +86,11 @@ def get_scheme(
         raise InvalidSchemeCombination("--home", "--prefix")
 
     if home is not None:
-        scheme = _infer_scheme("home")
+        scheme_name = _infer_scheme("home")
     elif user:
-        scheme = _infer_scheme("user")
+        scheme_name = _infer_scheme("user")
     else:
-        scheme = _infer_scheme("prefix")
+        scheme_name = _infer_scheme("prefix")
 
     if home is not None:
         variables = {k: home for k in _HOME_KEYS}
@@ -99,7 +99,7 @@ def get_scheme(
     else:
         variables = {}
 
-    paths = sysconfig.get_paths(scheme=scheme, vars=variables)
+    paths = sysconfig.get_paths(scheme=scheme_name, vars=variables)
 
     # Special header path for compatibility to distutils.
     if running_under_virtualenv():
@@ -126,21 +126,22 @@ def get_bin_prefix():
     # Forcing to use /usr/local/bin for standard macOS framework installs.
     if sys.platform[:6] == "darwin" and sys.prefix[:16] == "/System/Library/":
         return "/usr/local/bin"
-    return sysconfig.get_path("scripts", scheme=_infer_scheme("prefix"))
+    return sysconfig.get_paths(scheme=_infer_scheme("prefix"))["scripts"]
 
 
 def get_bin_user():
-    return sysconfig.get_path("scripts", scheme=_infer_scheme("user"))
+    # type: () -> str
+    return sysconfig.get_paths(scheme=_infer_scheme("user"))["scripts"]
 
 
 def get_purelib():
     # type: () -> str
-    return sysconfig.get_path("purelib")
+    return sysconfig.get_paths()["purelib"]
 
 
 def get_platlib():
     # type: () -> str
-    return sysconfig.get_path("platlib")
+    return sysconfig.get_paths()["platlib"]
 
 
 def get_prefixed_libs(prefix):

src/pip/_internal/locations/base.py

@@ -43,6 +43,6 @@ def get_src_prefix():
 try:
     # Use getusersitepackages if this is present, as it ensures that the
     # value is initialised properly.
-    user_site = site.getusersitepackages()
+    user_site = site.getusersitepackages()  # type: typing.Optional[str]
 except AttributeError:
     user_site = site.USER_SITE