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915576935a
Use `Option<Ident>` for lowered param names. Parameter patterns are lowered to an `Ident` by `lower_fn_params_to_names`, which is used when lowering bare function types, trait methods, and foreign functions. Currently, there are two exceptional cases where the lowered param can become an empty `Ident`. - If the incoming pattern is an empty `Ident`. This occurs if the parameter is anonymous, e.g. in a bare function type. - If the incoming pattern is neither an ident nor an underscore. Any such parameter will have triggered a compile error (hence the `span_delayed_bug`), but lowering still occurs. This commit replaces these empty `Ident` results with `None`, which eliminates a number of `kw::Empty` uses, and makes it impossible to fail to check for these exceptional cases. Note: the `FIXME` comment in `is_unwrap_or_empty_symbol` is removed. It actually should have been removed in #138482, the precursor to this PR. That PR changed the lowering of wild patterns to `_` symbols instead of empty symbols, which made the mentioned underscore check load-bearing. r? ``@compiler-errors`` |
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| README.md | ||
For high-level intro to how type checking works in rustc, see the type checking chapter of the rustc dev guide.