MyPy doesn't report any errors when using TypeVars within TypeVar constraints

[dadus33]

Bug Report

According to this, using TypeVars to constraint other TypeVars is not possible. However, MyPy doesn't report any errors in such cases.

To Reproduce

https://mypy-play.net/?mypy=latest&python=3.11&gist=e4febb3ef7aeaa11ea0aaabd4a068739

Expected Behavior

Some error should be reported

Actual Behavior

No error is reported

Your Environment

• Mypy version used: 1.9.0
• Mypy command-line flags: N/A
• Mypy configuration options from mypy.ini (and other config files): N/A
• Python version used: 3.11

[erictraut]

FWIW, I just updated the typing spec conformance tests to validate this part of the spec. Previously, the tests were attempting to validate this, but they were written in a way that masked the false negative in mypy. The updated tests correctly identify this conformance failure, and this is reflected in the latest conformance results summary.