## Summary
This PR closesastral-sh/ty#164.
This PR introduces a basic type narrowing mechanism for
attribute/subscript expressions.
Member accesses, int literal subscripts, string literal subscripts are
supported (same as mypy and pyright).
## Test Plan
New test cases are added to `mdtest/narrow/complex_target.md`.
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Co-authored-by: David Peter <mail@david-peter.de>
## Summary
This is sort of an anticlimactic resolution to #17863, but now that we
understand what the root cause for the stack overflows was, I think it's
fine to enable running on this project. See the linked ticket for the
full analysis.
closes#17863
## Test Plan
Ran lots of times locally and never observed a crash at worker thread
stack sizes > 8 MiB.
