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ruff/crates/red_knot_python_semantic/resources/mdtest/subscript/string.md
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[red-knot] Type narrow in else clause (#13918) 
## Summary

Add support for type narrowing in elif and else scopes as part of
#13694.

## Test Plan

- mdtest
- builder unit test for union negation.

---------

Co-authored-by: Carl Meyer <carl@astral.sh>
2024-10-26 16:22:57 +00:00

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Subscript on strings

Simple

s = "abcde"

reveal_type(s[0])  # revealed: Literal["a"]
reveal_type(s[1])  # revealed: Literal["b"]
reveal_type(s[-1])  # revealed: Literal["e"]
reveal_type(s[-2])  # revealed: Literal["d"]

reveal_type(s[False])  # revealed: Literal["a"]
reveal_type(s[True])  # revealed: Literal["b"]

a = s[8]  # error: [index-out-of-bounds] "Index 8 is out of bounds for string `Literal["abcde"]` with length 5"
reveal_type(a)  # revealed: Unknown

b = s[-8]  # error: [index-out-of-bounds] "Index -8 is out of bounds for string `Literal["abcde"]` with length 5"
reveal_type(b)  # revealed: Unknown

Function return

def int_instance() -> int:
    return 42

a = "abcde"[int_instance()]
# TODO: Support overloads... Should be `str`
reveal_type(a)  # revealed: @Todo