@AlexWaygood pointed out that the `SliceLiteral` type variant was originally created to handle slices before we had generics. https://github.com/astral-sh/ruff/pull/17927#discussion_r2078115787 Now that we _do_ have generics, we can use a specialization of the `slice` builtin type for slice literals. This depends on https://github.com/astral-sh/ruff/pull/17956, since we need to make sure that all typevar defaults are fully substituted when specializing `slice`.
Markdown files within the mdtest/ subdirectory are tests of type inference and type checking;
executed by the tests/mdtest.rs integration test.
See crates/ty_test/README.md for documentation of this test format.