Use TYPE_CHECKING instead of False

This allows for e.g. Jedi to infer types.

It was only used to support Python 3.5.0/3.5.1, where this is available
in `typing_extensions`.

Ref: davidhalter/jedi#1472

doc/en/conf.py

@@ -20,7 +20,11 @@
 
 from _pytest import __version__ as version
 
-if False:  # TYPE_CHECKING
+try:
+    from typing import TYPE_CHECKING
+except ImportError:
+    from typing_extensions import TYPE_CHECKING
+if TYPE_CHECKING:
     import sphinx.application
 
 

src/_pytest/_code/code.py

@@ -33,7 +33,11 @@
 from _pytest._io.saferepr import saferepr
 from _pytest.compat import overload
 
-if False:  # TYPE_CHECKING
+try:
+    from typing import TYPE_CHECKING
+except ImportError:
+    from typing_extensions import TYPE_CHECKING
+if TYPE_CHECKING:
     from typing import Type
     from typing_extensions import Literal
     from weakref import ReferenceType  # noqa: F401

src/_pytest/compat.py

@@ -28,7 +28,11 @@
 from _pytest.outcomes import fail
 from _pytest.outcomes import TEST_OUTCOME
 
-if False:  # TYPE_CHECKING
+try:
+    from typing import TYPE_CHECKING
+except ImportError:
+    from typing_extensions import TYPE_CHECKING
+if TYPE_CHECKING:
     from typing import Type  # noqa: F401 (used in type string)
 
 

src/_pytest/config/__init__.py

@@ -42,7 +42,11 @@
 from _pytest.pathlib import Path
 from _pytest.warning_types import PytestConfigWarning
 
-if False:  # TYPE_CHECKING
+try:
+    from typing import TYPE_CHECKING
+except ImportError:
+    from typing_extensions import TYPE_CHECKING
+if TYPE_CHECKING:
     from typing import Type
 
     from .argparsing import Argument

src/_pytest/config/argparsing.py

@@ -17,7 +17,11 @@
 
 from _pytest.config.exceptions import UsageError
 
-if False:  # TYPE_CHECKING
+try:
+    from typing import TYPE_CHECKING
+except ImportError:
+    from typing_extensions import TYPE_CHECKING
+if TYPE_CHECKING:
     from typing import NoReturn
     from typing_extensions import Literal  # noqa: F401
 

src/_pytest/doctest.py

@@ -24,7 +24,11 @@
 from _pytest.python_api import approx
 from _pytest.warning_types import PytestWarning
 
-if False:  # TYPE_CHECKING
+try:
+    from typing import TYPE_CHECKING
+except ImportError:
+    from typing_extensions import TYPE_CHECKING
+if TYPE_CHECKING:
     import doctest
     from typing import Type
 

src/_pytest/fixtures.py

@@ -32,7 +32,11 @@
 from _pytest.outcomes import fail
 from _pytest.outcomes import TEST_OUTCOME
 
-if False:  # TYPE_CHECKING
+try:
+    from typing import TYPE_CHECKING
+except ImportError:
+    from typing_extensions import TYPE_CHECKING
+if TYPE_CHECKING:
     from typing import Type
 
     from _pytest import nodes

src/_pytest/nodes.py

@@ -27,7 +27,11 @@
 from _pytest.mark.structures import NodeKeywords
 from _pytest.outcomes import Failed
 
-if False:  # TYPE_CHECKING
+try:
+    from typing import TYPE_CHECKING
+except ImportError:
+    from typing_extensions import TYPE_CHECKING
+if TYPE_CHECKING:
     # Imported here due to circular import.
     from _pytest.main import Session  # noqa: F401
 

src/_pytest/outcomes.py

@@ -8,7 +8,11 @@
 
 from packaging.version import Version
 
-if False:  # TYPE_CHECKING
+try:
+    from typing import TYPE_CHECKING
+except ImportError:
+    from typing_extensions import TYPE_CHECKING
+if TYPE_CHECKING:
     from typing import NoReturn
 
 

src/_pytest/pytester.py

@@ -35,7 +35,11 @@
 from _pytest.pathlib import Path
 from _pytest.reports import TestReport
 
-if False:  # TYPE_CHECKING
+try:
+    from typing import TYPE_CHECKING
+except ImportError:
+    from typing_extensions import TYPE_CHECKING
+if TYPE_CHECKING:
     from typing import Type
 
 
@@ -189,7 +193,7 @@ def __repr__(self):
         del d["_name"]
         return "<ParsedCall {!r}(**{!r})>".format(self._name, d)
 
-    if False:  # TYPE_CHECKING
+    if TYPE_CHECKING:
         # The class has undetermined attributes, this tells mypy about it.
         def __getattr__(self, key):
             raise NotImplementedError()

src/_pytest/python_api.py

@@ -25,7 +25,11 @@
 from _pytest.compat import STRING_TYPES
 from _pytest.outcomes import fail
 
-if False:  # TYPE_CHECKING
+try:
+    from typing import TYPE_CHECKING
+except ImportError:
+    from typing_extensions import TYPE_CHECKING
+if TYPE_CHECKING:
     from typing import Type  # noqa: F401 (used in type string)
 
 

src/_pytest/recwarn.py

@@ -15,7 +15,11 @@
 from _pytest.fixtures import yield_fixture
 from _pytest.outcomes import fail
 
-if False:  # TYPE_CHECKING
+try:
+    from typing import TYPE_CHECKING
+except ImportError:
+    from typing_extensions import TYPE_CHECKING
+if TYPE_CHECKING:
     from typing import Type
 
 

src/_pytest/runner.py

@@ -20,7 +20,11 @@
 from _pytest.outcomes import Skipped
 from _pytest.outcomes import TEST_OUTCOME
 
-if False:  # TYPE_CHECKING
+try:
+    from typing import TYPE_CHECKING
+except ImportError:
+    from typing_extensions import TYPE_CHECKING
+if TYPE_CHECKING:
     from typing import Type
 
 #

src/_pytest/warning_types.py

@@ -5,7 +5,11 @@
 import attr
 
 
-if False:  # TYPE_CHECKING
+try:
+    from typing import TYPE_CHECKING
+except ImportError:
+    from typing_extensions import TYPE_CHECKING
+if TYPE_CHECKING:
     from typing import Type  # noqa: F401 (used in type string)