rebase against source

src/pip/_internal/req/req_install.py

@@ -192,12 +192,17 @@ def __init__(
 
     @property
     def req(self) -> Optional[Requirement]:
-        """Calculate a requirement from the cached dist if necessary."""
+        """Calculate a requirement from the cached dist, if populated.
+
+        The cached dist can be populated by either
+        ``self.cache_virtual_metadata_only_dist()`` or
+        ``self.cache_concrete_dist()`` and can also be retrieved with
+        ``self.get_dist()``."""
         if self._req is not None:
             return self._req
-        if self._cached_dist is not None:
-            name = self._cached_dist.canonical_name
-            version = str(self._cached_dist.version)
+        if self._dist is not None:
+            name = self._dist.canonical_name
+            version = str(self._dist.version)
             self._req = Requirement(f"{name}=={version}")
             return self._req
         return None