diff --git a/src/pip/_internal/models/candidate.py b/src/pip/_internal/models/candidate.py
index c736de6c9af..4475458ab3d 100644
--- a/src/pip/_internal/models/candidate.py
+++ b/src/pip/_internal/models/candidate.py
@@ -1,6 +1,12 @@
 from pip._vendor.packaging.version import parse as parse_version
 
 from pip._internal.utils.models import KeyBasedCompareMixin
+from pip._internal.utils.typing import MYPY_CHECK_RUNNING
+
+if MYPY_CHECK_RUNNING:
+    from pip._vendor.packaging.version import _BaseVersion  # noqa: F401
+    from pip._internal.models.link import Link  # noqa: F401
+    from typing import Any, Union  # noqa: F401
 
 
 class InstallationCandidate(KeyBasedCompareMixin):
@@ -8,8 +14,9 @@ class InstallationCandidate(KeyBasedCompareMixin):
     """
 
     def __init__(self, project, version, location):
+        # type: (Any, str, Link) -> None
         self.project = project
-        self.version = parse_version(version)
+        self.version = parse_version(version)  # type: _BaseVersion
         self.location = location
 
         super(InstallationCandidate, self).__init__(
@@ -18,6 +25,7 @@ def __init__(self, project, version, location):
         )
 
     def __repr__(self):
+        # type: () -> str
         return "<InstallationCandidate({!r}, {!r}, {!r})>".format(
             self.project, self.version, self.location,
         )
diff --git a/src/pip/_internal/models/index.py b/src/pip/_internal/models/index.py
index 870a315ed1d..ead1efbda76 100644
--- a/src/pip/_internal/models/index.py
+++ b/src/pip/_internal/models/index.py
@@ -6,6 +6,7 @@ class PackageIndex(object):
     """
 
     def __init__(self, url, file_storage_domain):
+        # type: (str, str) -> None
         super(PackageIndex, self).__init__()
         self.url = url
         self.netloc = urllib_parse.urlsplit(url).netloc
@@ -18,6 +19,7 @@ def __init__(self, url, file_storage_domain):
         self.file_storage_domain = file_storage_domain
 
     def _url_for_path(self, path):
+        # type: (str) -> str
         return urllib_parse.urljoin(self.url, path)
 
 
diff --git a/src/pip/_internal/models/link.py b/src/pip/_internal/models/link.py
index 83c72657009..ad2f93e191a 100644
--- a/src/pip/_internal/models/link.py
+++ b/src/pip/_internal/models/link.py
@@ -8,6 +8,11 @@
     WHEEL_EXTENSION, redact_password_from_url, splitext,
 )
 from pip._internal.utils.models import KeyBasedCompareMixin
+from pip._internal.utils.typing import MYPY_CHECK_RUNNING
+
+if MYPY_CHECK_RUNNING:
+    from typing import Optional, Tuple, Union, Text  # noqa: F401
+    from pip._internal.index import HTMLPage  # noqa: F401
 
 
 class Link(KeyBasedCompareMixin):
@@ -15,6 +20,7 @@ class Link(KeyBasedCompareMixin):
     """
 
     def __init__(self, url, comes_from=None, requires_python=None):
+        # type: (str, Optional[Union[str, HTMLPage]], Optional[str]) -> None
         """
         url:
             url of the resource pointed to (href of the link)
@@ -55,6 +61,7 @@ def __repr__(self):
 
     @property
     def filename(self):
+        # type: () -> str
         _, netloc, path, _, _ = urllib_parse.urlsplit(self.url)
         name = posixpath.basename(path.rstrip('/')) or netloc
         name = urllib_parse.unquote(name)
@@ -63,25 +70,31 @@ def filename(self):
 
     @property
     def scheme(self):
+        # type: () -> str
         return urllib_parse.urlsplit(self.url)[0]
 
     @property
     def netloc(self):
+        # type: () -> str
         return urllib_parse.urlsplit(self.url)[1]
 
     @property
     def path(self):
+        # type: () -> str
         return urllib_parse.unquote(urllib_parse.urlsplit(self.url)[2])
 
     def splitext(self):
+        # type: () -> Tuple[str, str]
         return splitext(posixpath.basename(self.path.rstrip('/')))
 
     @property
     def ext(self):
+        # type: () -> str
         return self.splitext()[1]
 
     @property
     def url_without_fragment(self):
+        # type: () -> str
         scheme, netloc, path, query, fragment = urllib_parse.urlsplit(self.url)
         return urllib_parse.urlunsplit((scheme, netloc, path, query, None))
 
@@ -89,6 +102,7 @@ def url_without_fragment(self):
 
     @property
     def egg_fragment(self):
+        # type: () -> Optional[str]
         match = self._egg_fragment_re.search(self.url)
         if not match:
             return None
@@ -98,6 +112,7 @@ def egg_fragment(self):
 
     @property
     def subdirectory_fragment(self):
+        # type: () -> Optional[str]
         match = self._subdirectory_fragment_re.search(self.url)
         if not match:
             return None
@@ -109,6 +124,7 @@ def subdirectory_fragment(self):
 
     @property
     def hash(self):
+        # type: () -> Optional[str]
         match = self._hash_re.search(self.url)
         if match:
             return match.group(2)
@@ -116,6 +132,7 @@ def hash(self):
 
     @property
     def hash_name(self):
+        # type: () -> Optional[str]
         match = self._hash_re.search(self.url)
         if match:
             return match.group(1)
@@ -123,14 +140,17 @@ def hash_name(self):
 
     @property
     def show_url(self):
+        # type: () -> Optional[str]
         return posixpath.basename(self.url.split('#', 1)[0].split('?', 1)[0])
 
     @property
     def is_wheel(self):
+        # type: () -> bool
         return self.ext == WHEEL_EXTENSION
 
     @property
     def is_artifact(self):
+        # type: () -> bool
         """
         Determines if this points to an actual artifact (e.g. a tarball) or if
         it points to an "abstract" thing like a path or a VCS location.