PEP 593 aliasing Annotated is not working (type of instance is TypeVar instead of the actual type) #7729
Description
I'm running mypy 222b14d and Python 3.7.4. I added the following code to the test suite:
diff --git a/test-data/unit/check-annotated.test b/test-data/unit/check-annotated.test
index 1eaec3805d63..239ba2f13961 100644
--- a/test-data/unit/check-annotated.test
+++ b/test-data/unit/check-annotated.test
@@ -63,3 +63,11 @@ reveal_type(x) # N: Revealed type is 'Any'
[case testAnnotatedNoImport]
x: Annotated[int, ...] # E: Name 'Annotated' is not defined
reveal_type(x) # N: Revealed type is 'Any'
+
+[case testAnnotatedAlias]
+from typing import TypeVar
+from typing_extensions import Annotated
+T = TypeVar('T')
+Alias = Annotated[T, ...]
+x: Alias[int]
+reveal_type(x) # N: Revealed type is 'builtins.int'The tests fail with:
mypy% pytest -k "Annotated"
============================================================================================================ test session starts =============================================================================================================
platform darwin -- Python 3.7.4, pytest-3.10.1, py-1.8.0, pluggy-0.9.0
rootdir: /Users/user/projects/mypy, inifile: pytest.ini
plugins: xdist-1.25.0, forked-0.2, cov-2.5.1
gw0 [32] / gw1 [32] / gw2 [32] / gw3 [32] / gw4 [32] / gw5 [32] / gw6 [32] / gw7 [32]
..............................F. [100%]
================================================================================================================== FAILURES ==================================================================================================================
_____________________________________________________________________________________________________________ testAnnotatedAlias _____________________________________________________________________________________________________________
[gw6] darwin -- Python 3.7.4 /Users/user/.ve37/bin/python
data: /Users/user/projects/mypy/test-data/unit/check-annotated.test:67:
/Users/user/projects/mypy/mypy/test/testcheck.py:127: in run_case
self.run_case_once(testcase)
/Users/user/projects/mypy/mypy/test/testcheck.py:222: in run_case_once
assert_string_arrays_equal(output, a, msg.format(testcase.file, testcase.line))
/Users/user/projects/mypy/mypy/test/helpers.py:116: in assert_string_arrays_equal
raise AssertionError(msg)
E AssertionError: Unexpected type checker output (/Users/user/projects/mypy/test-data/unit/check-annotated.test, line 67)
------------------------------------------------------------------------------------------------------------ Captured stderr call ------------------------------------------------------------------------------------------------------------
Expected:
main:6: note: Revealed type is 'builtins.int' (diff)
Actual:
main:6: note: Revealed type is 'T?' (diff)
Alignment of first line difference:
E: ...te: Revealed type is 'builtins.int'
A: ...te: Revealed type is 'T?'
^
This is a bug I believe. I noticed this when I wanted to trigger mypy error when type-checking code that uses Annotated aliases and failed. I'd create a patch for this but I'm out of my depth when it comes to mypy type analysis, so the next best thing is to report this.