Merge branch 'master' into omit_type_checking

Author: PetterS

.travis.yml

@@ -12,5 +12,10 @@ matrix:
       dist: xenial
     - python: nightly
       dist: xenial
+# TODO: https://bugs.python.org/issue40334
+# the PEG parser is currently broken in some cases
+  allow_failures:
+    - python: nightly
+      dist: xenial
 install: pip install tox
 script: tox -e py

pyflakes/test/test_api.py

@@ -449,6 +449,8 @@ def evaluate(source):
         with self.makeTempFile(source) as sourcePath:
             if PYPY:
                 message = 'end of file (EOF) while scanning triple-quoted string literal'
+            elif sys.version_info >= (3, 9):
+                message = 'invalid string prefix'
             else:
                 message = 'invalid syntax'
 

pyflakes/test/test_type_annotations.py

@@ -552,3 +552,47 @@ def test_partial_string_annotations_with_future_annotations(self):
             def f() -> Optional['Queue[str]']:
                 return None
         """)
+
+    def test_idomiatic_typing_guards(self):
+        # typing.TYPE_CHECKING: python3.5.3+
+        self.flakes("""
+            from typing import TYPE_CHECKING
+
+            if TYPE_CHECKING:
+                from t import T
+
+            def f():  # type: () -> T
+                pass
+        """)
+        # False: the old, more-compatible approach
+        self.flakes("""
+            if False:
+                from t import T
+
+            def f():  # type: () -> T
+                pass
+        """)
+        # some choose to assign a constant and do it that way
+        self.flakes("""
+            MYPY = False
+
+            if MYPY:
+                from t import T
+
+            def f():  # type: () -> T
+                pass
+        """)
+
+    def test_typing_guard_for_protocol(self):
+        self.flakes("""
+            from typing import TYPE_CHECKING
+
+            if TYPE_CHECKING:
+                from typing import Protocol
+            else:
+                Protocol = object
+
+            class C(Protocol):
+                def f():  # type: () -> int
+                    pass
+        """)